UP-CONVERSION BASED ON GATED INFORMATION SIGNAL
A method and system is described wherein an information signal is gated at a frequency that is a sub-harmonic of the frequency of the desired output signal. In the modulation embodiments, the information signal is modulated as part of the up-conversion process. In a first modulation embodiment, one information signal is phase modulated onto the carrier signal as part of the up-conversion process. In a second modulation embodiment, two information signals are multiplied, and, as part of the up-conversion process, one signal is phase modulated onto the carrier and the other signal is amplitude modulated onto the carrier. In a third modulation embodiment, one information signal is phase modulated onto the “I” phase of the carrier signal as part of the up-conversion process and a second information signal is phase modulated onto the “Q” phase of the carrier as part of the up-conversion process.
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This is a continuation application of pending U.S. patent application Ser. No. 12/615,326, titled, “Up-Conversion Based On Gated Information Signal,” filed on Nov. 10, 2009, which is a continuation of U.S. Pat. No. 7,620,378, titled, “Method And System for Frequency Up-Conversion with Modulation Embodiments,” filed on Jul. 16, 2007, which is a continuation of U.S. Pat. No. 7,245,886, titled, “Method and System for Frequency Up-conversion With Modulation Embodiments, filed Feb. 3, 2005, which is a continuation of application of U.S. Pat. No. 7,039,372, titled, “Method and System for Frequency Up-Conversion With Modulation Embodiments,” filed Apr. 13, 2000, which is a continuation-in-part application of U.S. Pat. No. 6,353,735, titled “Method for Output Signal Generation,” filed Aug. 23, 1999, which is a continuation of U.S. Pat. No. 6,091,940, titled “Method and System for Frequency Up-Conversion,” filed Oct. 21, 1998, all of which are incorporated herein by reference in their entireties.
CROSS-REFERENCE TO OTHER APPLICATIONSThe following applications of common assignee are related to the present application, and are herein incorporated by reference in their entireties:
“Method and System for Down-Converting Electromagnetic Signals,” Ser. No. 09/176,022, filed Oct. 21, 1998.
“Method and System for Ensuring Reception of a Communications Signal,” Ser. No. 09/176,415, filed Oct. 21, 1998.
“Integrated Frequency Translation and Selectivity,” Ser. No. 09/175,966, filed Oct. 21, 1998, U.S. Pat. No. 6,049,706.
“Applications of Universal Frequency Translation,” Ser. No. 09/261,129, filed Mar. 3, 1999.
“Method and System for Down-Converting Electromagnetic Signals Having Optimized Switch Structures,” Ser. No. 09/293,095, filed Apr. 16, 1999.
“Method and System for Down-Converting Electromagnetic Signals Including Resonant Structures for Enhanced Energy Transfer,” Ser. No. 09/293,342, filed Apr. 16, 1999.
“Method and System for Frequency Up-Conversion With a Variety of Transmitter Configurations,” Ser. No. 09/293,580, filed Apr. 16, 1999.
“Integrated Frequency Translation And Selectivity With a Variety of Filter Embodiments,” Ser. No. 09/293,283, filed Apr. 16, 1999.
BACKGROUND OF THE INVENTION1. Field of the Invention
The present invention is generally directed to frequency up-conversion of electromagnetic (EM) signals.
2. Related Art
Modern day communication systems employ components such as transmitters and receivers to transmit information from a source to a destination. To accomplish this transmission, information is imparted on a carrier signal and the carrier signal is then transmitted. Typically, the carrier signal is at a frequency higher than the baseband frequency of the information signal. Typical ways that the information is imparted on the carrier signal are called modulation.
Three widely used modulation schemes include: frequency modulation (FM), where the frequency of the carrier wave changes to reflect the information that has been modulated on the signal; phase modulation (PM), where the phase of the carrier signal changes to reflect the information imparted on it; and amplitude modulation (AM), where the amplitude of the carrier signal changes to reflect the information. Also, these modulation schemes are used in combination with each other (e.g., AM combined with FM and AM combined with PM).
SUMMARY OF THE INVENTIONThe present invention is directed to methods and systems to up-convert a signal from a lower frequency to a higher frequency, and applications thereof.
In one embodiment, the invention uses a stable, low frequency signal to generate a higher frequency signal with a frequency and phase that can be used as stable references.
In another embodiment, the present invention is used as a transmitter. In this embodiment, the invention accepts an information signal at a baseband frequency and transmits a modulated signal at a frequency higher than the baseband frequency.
The methods and systems of transmitting vary slightly depending on the modulation scheme being used. For some embodiments using frequency modulation (FM) or phase modulation (PM), the information signal is used to modulate an oscillating signal to create a modulated intermediate signal. If needed, this modulated intermediate signal is “shaped” to provide a substantially optimum pulse-width-to-period ratio. This shaped signal is then used to control a switch which opens and closes as a function of the frequency and pulse width of the shaped signal. As a result of this opening and closing, a signal that is harmonically rich is produced with each harmonic of the harmonically rich signal being modulated substantially the same as the modulated intermediate signal. Through proper filtering, the desired harmonic (or harmonics) is selected and transmitted.
For some embodiments using amplitude modulation (AM), the switch is controlled by an unmodulated oscillating signal (which may, if needed, be shaped). As the switch opens and closes, it gates a reference signal which is the information signal. In an alternate implementation, the information signal is combined with a bias signal to create the reference signal, which is then gated. The result of the gating is a harmonically rich signal having a fundamental frequency substantially proportional to the oscillating signal and an amplitude substantially proportional to the amplitude of the reference signal. Each of the harmonics of the harmonically rich signal also have amplitudes proportional to the reference signal, and are thus considered to be amplitude modulated. Just as with the FM/PM embodiments described above, through proper filtering, the desired harmonic (or harmonics) is selected and transmitted.
Further features and advantages of the invention, as well as the structure and operation of various embodiments of the invention, are described in detail below with reference to the accompanying figures. The left-most digit(s) of a reference number typically identifies the figure in which the reference number first appears.
FIGS. 64A and 64A1 illustrate exemplary implementations of aliasing modules;
FIG. 65—illustrates an exemplary circuit for a first implementation for phase modulating an information signal as part of the up-conversion process;
FIG. 66—illustrates an exemplary circuit for a first implementation for phase modulating one information signal and amplitude modulating a second information signal as part of the up-conversion process;
FIG. 67—illustrates an exemplary circuit for a second implementation for phase modulating an information signal as part of the up-conversion process;
FIG. 68—illustrates an exemplary circuit for a second implementation for phase modulating one information signal and amplitude modulating a second information signal as part of the up-conversion process;
FIG. 69—illustrates an exemplary circuit for a first implementation for phase modulating one information signal onto the “I” phase of a carrier and for phase modulating a second information signal onto the “Q” phase of a carrier as part of the up-conversion process;
FIG. 70—illustrates an exemplary circuit for a second implementation for phase modulating one information signal onto the “I” phase of a carrier and for phase modulating a second information signal onto the “Q” phase of a carrier as part of the up-conversion process;
FIG. 71—illustrates an exemplary circuit for phase modulating a first information signal and amplitude modulating a second information signal onto the “I” phase of a carrier, and for phase modulating a third information signal and amplitude modulating a fourth information signal onto the “Q” phase of a carrier as part of the up-conversion process;
2.1 Discussion of Modulation Techniques.
2.2 Explanation of Exemplary Circuits and Waveforms.
-
- 2.2.1 Frequency Modulation.
- 2.2.2 Phase Modulation.
- 2.2.3 Amplitude Modulation.
- 2.2.4 In-phase/Quadrature-phase Modulation.
2.3 Features of the Invention.
3. Frequency Up-conversion.3.1 High Level Description.
-
- 3.1.1 Operational Description.
- 3.1.2 Structural Description.
3.2 Exemplary Embodiments.
-
- 3.2.1 First Embodiment: Frequency Modulation (FM) Mode.
- 3.2.1.1 Operational Description.
- 3.2.1.2 Structural Description.
- 3.2.2 Second Embodiment: Phase Modulation (PM) Mode.
- 3.2.2.1 Operational Description.
- 3.2.2.2 Structural Description.
- 3.2.3 Third Embodiment: Amplitude Modulation (AM) Mode.
- 3.2.3.1 Operational Description.
- 3.2.3.2 Structural Description.
- 3.2.4 Fourth Embodiment: In-phase/Quadrature-phase (“I/Q”) Modulation Mode.
- 3.2.4.1 Operational Description.
- 3.2.4.2 Structural Description.
- 3.2.5 Other Embodiments.
- 3.2.5.1 Combination of Modulation Techniques
- 3.2.5.2 Modulation as Part of the Up-Conversion Process.
- 3.2.1 First Embodiment: Frequency Modulation (FM) Mode.
3.3 Methods and Systems for Implementing the Embodiments.
-
- 3.3.1 The Voltage Controlled Oscillator (FM Mode).
- 3.3.1.1 Operational Description.
- 3.3.1.2 Structural Description.
- 3.3.2 The Local Oscillator (PM, AM, and “I/Q” Modes).
- 3.3.2.1 Operational Description.
- 3.3.2.2 Structural Description.
- 3.3.3 The Phase Shifter (PM Mode).
- 3.3.3.1 Operational Description.
- 3.3.3.2 Structural Description.
- 3.3.4 The Phase Modulator (PM and “I/Q” Modes).
- 3.3.4.1 Operational Description.
- 3.3.4.2 Structural Description.
- 3.3.5 The Summing Module (AM Mode).
- 3.3.5.1 Operational Description.
- 3.3.5.2 Structural Description.
- 3.3.6 The Switch Module (FM, PM, and “I/Q” Modes).
- 3.3.6.1 Operational Description.
- 3.3.6.2 Structural Description.
- 3.3.7 The Switch Module (AM Mode).
- 3.3.7.1 Operational Description.
- 3.3.7.2 Structural Description.
- 3.3.8 The Summer (“I/Q” Mode).
- 3.3.8.1 Operational Description.
- 3.3.8.2 Structural Description.
- 3.3.9 The Filter (FM, PM, AM, and “I/Q” Modes).
- 3.3.9.1 Operational Description.
- 3.3.9.2 Structural Description.
- 3.3.10 The Transmission Module (FM, PM, AM, and “I/Q” Modes).
- 3.3.10.1 Operational Description.
- 3.3.10.2 Structural Description.
- 3.3.11 Other Implementations.
- 3.3.1 The Voltage Controlled Oscillator (FM Mode).
4.1 High Level Description.
-
- 4.1.1 Operational Description.
- 4.1.2 Structural Description.
4.2 Exemplary Embodiments.
-
- 4.2.1 First Embodiment: When a Square Wave Feeds the Harmonic Enhancement Module to Create One Pulse per Cycle.
- 4.2.1.1 Operational Description.
- 4.2.1.2 Structural Description.
- 4.2.2 Second Embodiment: When a Square Wave Feeds the Harmonic Enhancement Module to Create Two Pulses per Cycle.
- 4.2.2.1 Operational Description.
- 4.2.2.2 Structural Description.
- 4.2.3 Third Embodiment: When Any Waveform Feeds the Harmonic Enhancement Module.
- 4.2.3.1 Operational Description.
- 4.2.3.2 Structural Description.
- 4.2.4 Other Embodiments.
- 4.2.1 First Embodiment: When a Square Wave Feeds the Harmonic Enhancement Module to Create One Pulse per Cycle.
4.3 Implementation Examples.
-
- 4.3.1 First Digital Logic Circuit.
- 4.3.2 Second Digital Logic Circuit.
- 4.3.3 Analog Circuit.
- 4.3.4 Other Implementations.
5.1 High Level Description.
-
- 5.1.1 Operational Description.
- 5.1.2 Structural Description.
5.2 Exemplary Embodiment.
-
- 5.2.1 Linear Amplifier.
- 5.2.1.1 Operational Description.
- 5.2.1.2 Structural Description.
- 5.2.2 Other Embodiments.
- 5.2.1 Linear Amplifier.
5.3 Implementation Examples.
-
- 5.3.1 Linear Amplifier.
- 5.3.1.1 Operational Description.
- 5.3.1.2 Structural Description.
- 5.3.2 Other Implementations.
- 5.3.1 Linear Amplifier.
6.1 High Level Description.
6.2 Exemplary Embodiments and Implementation Examples.
-
- 6.2.1 First Embodiment: The Transmitter of the Present Invention Being Used in a Circuit with a Superheterodyne Receiver.
- 6.2.2 Second Embodiment: The Transmitter of the Present Invention Being Used with a Universal Frequency Down Converter in a Half-Duplex Mode.
- 6.2.3 Third Embodiment: The Transmitter of the Present Invention Being Used with a Universal Frequency Down Converter in a Full-Duplex Mode.
- 6.2.4 Other Embodiments and Implementations.
6.3 Summary Description of Down-conversion Using a Universal Frequency Translation Module.
7. Designing a Transmitter According to an Embodiment of the Present Invention.7.1 Frequency of the Transmission Signal.
7.2 Characteristics of the Transmission Signal.
7.3 Modulation Scheme.
7.4 Characteristics of the Information Signal.
7.5 Characteristic of the Oscillating Signal.
-
- 7.5.1 Frequency of the Oscillating Signal.
- 7.5.2 Pulse Width of the String of Pulses.
7.6 Design of the Pulse Shaping Circuit.
7.7 Selection of the Switch.
-
- 7.7.1 Optimized Switch Structures.
- 7.7.2 Phased D2D—Splitter in CMOS
7.8 Design of the Filter.
7.9 Selection of an Amplifier.
7.10 Design of the Transmission Module.
1. TERMINOLOGYVarious terms used in this application are generally described in this section. Each description in this section is provided for illustrative and convenience purposes only, and is not limiting. The meaning of these terms will be apparent to persons skilled in the relevant art(s) based on the entirety of the teachings provided herein.
Amplitude Modulation (AM): A modulation technique wherein the amplitude of the carrier signal is shifted (i.e., varied) as a function of the information signal. The frequency of the carrier signal typically remains constant. A subset of AM is referred to as “amplitude shift keying” which is used primarily for digital communications where the amplitude of the carrier signal shifts between discrete states rather than varying continuously as it does for analog information.
Analog signal: A signal in which the information contained therein is continuous as contrasted to discrete, and represents a time varying physical event or quantity. The information content is conveyed by varying at least one characteristic of the signal, such as but not limited to amplitude, frequency, or phase, or any combinations thereof.
Baseband signal: Any generic information signal desired for transmission and/or reception. As used herein, it refers to both the information signal that is generated at a source prior to any transmission (also referred to as the modulating baseband signal), and to the signal that is to be used by the recipient after transmission (also referred to as the demodulated baseband signal).
Carrier signal: A signal capable of carrying information. Typically, it is an electromagnetic signal that can be varied through a process called modulation. The frequency of the carrier signal is referred to as the carrier frequency. A communications system may have multiple carrier signals at different carrier frequencies.
Control a switch: Causing a switch to open and close. The switch may be, without limitation, mechanical, electrical, electronic, optical, etc., or any combination thereof. Typically, it is controlled by an electrical or electronic input. If the switch is controlled by an electronic signal, it is typically a different signal than the signals connected to either terminal of the switch.
Demodulated baseband signal: The baseband signal that is to be used by the recipient after transmission. Typically it has been down converted from a carrier signal and has been demodulated. The demodulated baseband signal should closely approximate the information signal (i.e., the modulating baseband signal) in frequency, amplitude, and information.
Demodulation: The process of removing information from a carrier or intermediate frequency signal.
Digital signal: A signal in which the information contained therein has discrete states as contrasted to a signal that has a property that may be continuously variable.
Direct down conversion: A down conversion technique wherein a received signal is directly down converted and demodulated, if applicable, from the original transmitted frequency (i.e., a carrier frequency) to baseband without having an intermediate frequency.
Down conversion: A process for performing frequency translation in which the final frequency is lower than the initial frequency.
Drive a switch: Same as control a switch.
Frequency Modulation (FM): A modulation technique wherein the frequency of the carrier signal is shifted (i.e., varied) as a function of the information signal. A subset of FM is referred to as “frequency shift keying” which is used primarily for digital communications where the frequency of the carrier signal shifts between discrete states rather than varying continuously as it does for analog information.
Harmonic: A harmonic is a frequency or tone that, when compared to its fundamental or reference frequency or tone, is an integer multiple of it. In other words, if a periodic waveform has a fundamental frequency of “f” (also called the first harmonic), then its harmonics may be located at frequencies of “n·f,” where “n” is 2, 3, 4, etc. The harmonic corresponding to n=2 is referred to as the second harmonic, the harmonic corresponding to n=3 is referred to as the third harmonic, and so on.
In-phase (“I”) signal: The signal typically generated by an oscillator. It has not had its phase shifted and is often represented as a sine wave to distinguish it from a “Q” signal. The “I” signal can, itself, be modulated by any means. When the “I” signal is combined with a “Q” signal, the resultant signal is referred to as an “I/Q” signal.
In-phase/Quadrature-phase (“I/Q”) signal: The signal that results when an “I” signal is summed with a “Q” signal. Typically, both the “I” and “Q” signals have been phase modulated, although other modulation techniques may also be used, such as amplitude modulation. An “I/Q” signal is used to transmit separate streams of information simultaneously on a single transmitted carrier. Note that the modulated “I” signal and the modulated “Q” signal are both carrier signals having the same frequency. When combined, the resultant “I/Q” signal is also a carrier signal at the same frequency.
Information signal: The signal that contains the information that is to be transmitted. As used herein, it refers to the original baseband signal at the source. When it is intended that the information signal modulate a carrier signal, it is also referred to as the “modulating baseband signal.” It may be voice or data, analog or digital, or any other signal or combination thereof.
Intermediate frequency (IF) signal: A signal that is at a frequency between the frequency of the baseband signal and the frequency of the transmitted signal.
Modulation: The process of varying one or more physical characteristics of a signal to represent the information to be transmitted. Three commonly used modulation techniques are frequency modulation, phase modulation, and amplitude modulation. There are also variations, subsets, and combinations of these three techniques.
Operate a switch: Same as control a switch.
Phase Modulation (PM): A modulation technique wherein the phase of the carrier signal is shifted (i.e., varied) as a function of the information signal. A subset of PM is referred to as “phase shift keying” which is used primarily for digital communications where the phase of the carrier signal shifts between discrete states rather than varying continuously as it does for analog information.
Quadrature-phase (“Q”) signal: A signal that is out of phase with an in-phase (“I”) signal. The amount of phase shift is predetermined for a particular application, but in a typical implementation, the “Q” signal is 90° out of phase with the “I” signal. Thus, if the “I” signal were a sine wave, the “Q” signal would be a cosine wave. When discussed together, the “I” signal and the “Q” signal have the same frequencies.
Spectrum: Spectrum is used to signify a continuous range of frequencies, usually wide, within which electromagnetic (EM) waves have some specific common characteristic. Such waves may be propagated in any communication medium, both natural and manmade, including but not limited to air, space, wire, cable, liquid, waveguide, microstrip, stripline, optical fiber, etc. The EM spectrum includes all frequencies greater than zero hertz.
Subharmonic: A subharmonic is a frequency or tone that is an integer submultiple of a referenced fundamental frequency or tone. That is, a subharmonic frequency is the quotient obtained by dividing the fundamental frequency by an integer. For example, if a periodic waveform has a frequency of “f” (also called the “fundamental frequency” or first subharmonic), then its subharmonics have frequencies of “f/n,” where n is 2, 3, 4, etc. The subharmonic corresponding to n=2 is referred to as the second subharmonic, the subharmonic corresponding to n=3 is referred to as the third subharmonic, and so on. A subharmonic itself has possible harmonics, and the ith harmonic of the ith subharmonic will be at the fundamental frequency of the original periodic waveform. For example, the third subharmonic (which has a frequency of “f/3”) may have harmonics at integer multiples of itself (i.e., a second harmonic at “2·f/3,” a third harmonic at “3·f/3,” and so on). The third harmonic of the third subharmonic of the original signal (i.e., “3·f/3”) is at the frequency of the original signal.
Trigger a switch: Same as control a switch.
Up conversion: A process for performing frequency translation in which the final frequency is higher than the initial frequency.
2. OVERVIEW OF THE INVENTIONThe present invention is directed to systems and methods for frequency up-conversion, and applications thereof.
In one embodiment, the frequency up-converter of the present invention is used as a stable reference frequency source in a phase comparator or in a frequency comparator. This embodiment of the present invention achieves this through the use of a stable, low frequency local oscillator, a switch, and a filter. Because it up-converts frequency, the present invention can take advantage of the relatively low cost of low frequency oscillators to generate stable, high frequency signals.
In a second embodiment, the frequency up-converter is used as a system and method for transmitting an electromagnetic (EM) signal.
Based on the discussion contained herein, one skilled in the relevant art(s) will recognize that there are other, alternative embodiments in which the frequency up-converter of the present invention could be used in other applications, and that these alternative embodiments fall within the scope of the present invention.
For illustrative purposes, various modulation examples are discussed below. However, it should be understood that the invention is not limited by these examples. Other modulation techniques that might be used with the present invention will be apparent to persons skilled in the relevant art(s) based on the teaching contained herein.
Also for illustrative purposes, frequency up-conversion according to the present invention is described below in the context of a transmitter. However, the invention is not limited to this embodiment. Equivalents, extensions, variations, deviations, etc., of the following will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such equivalents, extensions, variations, deviations, etc., are within the scope and spirit of the present invention.
2.1 Discussion of Modulation Techniques.
Techniques by which information can be imparted onto EM signals to be transmitted are called modulation. These techniques are generally well known to one skilled in the relevant art(s), and include, but are not limited to, frequency modulation (FM), phase modulation (PM), amplitude modulation (AM), quadrature-phase shift keying (QPSK), frequency shift keying (FSK), phase shift keying (PSK), amplitude shift keying (ASK), etc., and combinations thereof. These last three modulation techniques, FSK, PSK, and ASK, are subsets of FM, PM, and AM, respectively, and refer to circuits having discrete input signals (e.g., digital input signals).
For illustrative purposes only, the circuits and techniques described below all refer to the EM broadcast medium. However, the invention is not limited by this embodiment. Persons skilled in the relevant art(s) will recognize that these same circuits and techniques can be used in all transmission media (e.g., over-the-air broadcast, point-to-point cable, etc.).
2.2 Explanation of Exemplary Circuits and Waveforms.
2.2.1 Frequency Modulation.
Frequency modulation circuit 100 receives an information signal 102, 2002 from a source (not shown). Information signal 102, 2002 can be amplified by an optional amplifier 104 and filtered by an optional filter 114 and is the voltage input that drives a voltage controlled oscillator (VCO) 106. Within VCO 106, an oscillating signal 202 (seen on
2.2.2 Phase Modulation.
Phase modulation circuit 300 receives information signal 302, 2102 from a source (not shown). Information signal 302, 2102 can be amplified by an optional amplifier 304 and filtered by an optional filter 318 and is routed to a phase modulator 306. Also feeding phase modulator 306 is LO output 308 of a local oscillator 310. LO output 308 is shown on
The output of phase modulator 306 is a modulated signal shown as a phase modulated signal 312 (
After information signal 302, 2102 and LO output 308 have been modulated by phase modulator 306, phase modulated signal 312, 2104 can be routed to an optional frequency multiplier 314 and optional amplifier 320. The purpose of optional frequency multiplier 314 is to increase the frequency of phase modulated signal 312 from a relatively low frequency (e.g., 50 MHz to 100 MHz) to a desired broadcast frequency (e.g., 900 MHz, 1.8 GHz). Optional amplifier 320 raises the signal strength of phase modulated signal 312, 2104 to a desired level to be transmitted by an exemplary antenna 316.
2.2.3 Amplitude Modulation.
Amplitude modulation circuit 500 receives information signal 502 from a source (not shown). Information signal 502, 2202 can be amplified by an optional amplifier 504 and filtered by an optional filter 518. Amplitude modulation circuit 500 also includes a local oscillator (LO) 506 which has an LO output 508. Information signal 502, 2202 and LO output 508 are then multiplied by a multiplier 510. The purpose of multiplier 510 is to cause the amplitude of LO output 508 to vary as a function of the amplitude of information signal 502, 2202. The output of multiplier 510 is a modulated signal shown as amplitude modulated signal 512 (
2.2.4 In-Phase/Quadrature-Phase Modulation.
This “I/Q” modulation system uses two PM circuits together in order to increase the bandwidth efficiency. As stated above, in a PM circuit, the phase of an oscillating signal, such as 710 (or 712) (
“I/Q” modulation circuit 700 receives an information signal 702 from a first source (not shown) and an information signal 704 from a second source (not shown). Examples of information signals 702 and 704 are shown in
The output of phase modulator 718 is a phase modulated signal 722 which is shown using a dotted line as one of the waveforms in
For simplicity of discussion and ease of display, oscillating signal 710 is shown on
“I/Q” signal 728 can then be routed to an optional frequency multiplier 730, where the frequency of “I/Q” signal 718 is increased from a relatively low level (e.g., 50 MHz to 100 MHz) to a higher level desired for broadcast (e.g., 900 MHz, 1.8 GHz), and to an optional amplifier 738 which increases the signal strength of “I/Q” signal 728 to a desired level for broadcast by an exemplary antenna 732.
2.3 Features of the Invention.
As apparent from the above, several frequencies are involved in a communications system. The frequency of the information signal is relatively low. The frequency of the local oscillator (both the voltage controlled oscillator as well as the other oscillators) is higher than that of the information signal, but typically not high enough for efficient transmission. A third frequency, not specifically mentioned above, is the frequency of the transmitted signal which is greater than or equal to the frequency of the oscillating signal. This is the frequency that is routed from the optional frequency multipliers and optional amplifiers to the antennas in the previously described circuits.
Typically, in the transmitter subsystem of a communications system, upconverting the information signal to broadcast frequency requires, at least, filters, amplifiers, and frequency multipliers. Each of these components is costly, not only in terms of the purchase price of the component, but also because of the power required to operate them.
The present invention provides a more efficient means for producing a modulated carrier for transmission, uses less power, and requires fewer components. These and additional advantages of the present invention will be apparent from the following description.
3. FREQUENCY UP-CONVERSIONThe present invention is directed to systems and methods for frequency up-conversion and applications of the same. In one embodiment, the frequency up-converter of the present invention allows the use of a stable, low frequency oscillator to generate a stable high frequency signal that, for example and without limitation, can be used as a reference signal in a phase comparator or a frequency comparator. In another embodiment, the up-converter of the present invention is used in a transmitter. The invention is also directed to a transmitter. Based on the discussion contained herein, one skilled in the relevant art(s) will recognize that there are other, alternative embodiments and applications in which the frequency up-converter of the present invention could be used, and that these alternative embodiments and applications fall within the scope of the present invention.
For illustrative purposes, frequency up-conversion according to the present invention is described below in the context of a transmitter. However, as apparent from the preceding paragraph, the invention is not limited to this embodiment.
The following sections describe methods related to a transmitter and frequency up-converter. Structural exemplary embodiments for achieving these methods are also described. It should be understood that the invention is not limited to the particular embodiments described below. Equivalents, extensions, variations, deviations, etc., of the following will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such equivalents, extensions, variations, deviations, etc., are within the scope and spirit of the present invention.
3.1. High Level DescriptionThis section (including its subsections) provides a high-level description of up-converting and transmitting signals according to the present invention. In particular, an operational process of frequency up-conversion in the context of transmitting signals is described at a high-level. The operational process is often represented by flowcharts. The flowcharts are presented herein for illustrative purposes only, and are not limiting. In particular, the use of flowcharts should not be interpreted as limiting the invention to discrete or digital operation. In practice, those skilled in the relevant art(s) will appreciate, based on the teachings contained herein, that the invention can be achieved via discrete operation, continuous operation, or any combination thereof. Furthermore, the flow of control represented by the flowcharts is also provided for illustrative purposes only, and it will be appreciated by persons skilled in the relevant art(s) that other operational control flows are within the scope and spirit of the invention.
Also, a structural implementation for achieving this process is described at a high-level. This structural implementation is described herein for illustrative purposes, and is not limiting. In particular, the process described in this section can be achieved using any number of structural implementations, one of which is described in this section. The details of such structural implementations will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein.
3.1.1 Operational Description.
The flow chart 900 of
In step 902, an information signal 1902 (
An oscillating signal 1904 (
A harmonically rich signal 1908 (
A continuous periodic waveform (such as waveform 1908) is composed of a series of sinusoidal waves of specific amplitudes and phases, the frequencies of which are integer multiples of the repetition frequency of the waveform. (A waveform's repetition frequency is the number of times per second the periodic waveform repeats.) A portion of the waveform of signal 1908 is shown in an expanded view as waveform 1910 of
In step 910, any unwanted harmonics of the continuous periodic waveform of signal 1908 are filtered out (for example, any harmonics that are not at frequencies desired to be transmitted). In the example of
3.1.2 Structural Description.
Preferably, the acceptance module 1004, harmonic generation and extraction module 1006, and transmission module 1008 process the information signal in the manner shown in the operational flowchart 900. In other words, transmitter 1000 is the structural embodiment for performing the operational steps of flowchart 900. However, it should be understood that the scope and spirit of the present invention includes other structural embodiments for performing the steps of flowchart 900. The specifics of these other structural embodiments will be apparent to persons skilled in the relevant art(s) based on the discussion contained herein.
The operation of the transmitter 1000 will now be described in detail with reference to the flowchart 900. In step 902, an information signal 1002 (for example, see
Various embodiments related to the method(s) and structure(s) described above are presented in this section (and its subsections). These embodiments are described herein for purposes of illustration, and not limitation. The invention is not limited to these embodiments. Alternate embodiments (including equivalents, extensions, variations, deviations, etc., of the embodiments described herein) will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. The invention is intended and adapted to include such alternate embodiments.
3.2.1 First Embodiment Frequency Modulation (FM) ModeIn this embodiment, an information signal is accepted and a modulated signal whose frequency varies as a function of the information signal results.
3.2.1.1 Operational Description.
The flow chart of
In step 1102, an information signal 1902 (
In step 1108, a harmonically rich signal with a continuous periodic waveform, shown in
As stated before, a continuous and periodic waveform, such as a rectangular wave 1908 as indicated in block 1110 of flowchart 1100, has sinusoidal components (harmonics) at frequencies that are integer multiples of the fundamental frequency of the underlying waveform (i.e., at the Fourier component frequencies). Three harmonics of periodic waveform 1910 are shown separately, in expanded views, in
In step 1112, the unwanted frequencies of waveform 1916 are removed. In the example of
The EM signal, shown here as remaining waveform 1918, is prepared for transmission in step 1116, and in step 1118, the EM signal is transmitted.
3.2.1.2 Structural Description.
Preferably, the voltage controlled oscillator 1204, switch module 1214, filter 1218, and transmission module 1222 process the information signal in the manner shown in the operational flowchart 1100. In other words, FM transmitter 1200 is the structural embodiment for performing the operational steps of flowchart 1100. However, it should be understood that the scope and spirit of the present invention includes other structural embodiments for performing the steps of flowchart 1100. The specifics of these other structural embodiments will be apparent to persons skilled in the relevant art(s) based on the discussion contained herein.
The operation of the transmitter 1200 will now be described in detail with reference to the flowchart 1100. In step 1102, an information signal 1202 (for example, see
In this embodiment, an information signal is accepted and a modulated signal whose phase varies as a function of the information signal is transmitted.
3.2.2.1 Operational Description.
The flow chart of
In step 1302, an information signal 4402 (
A harmonically rich signal 4408 (
The EM signal is prepared for transmission in step 1318, and in step 1320, the EM signal is transmitted.
3.2.2.2 Structural Description.
Preferably, the local oscillator 1406, phase modulator 1404, switch module 1410, filter 1414, and transmission module 1418 process the information signal in the manner shown in the operational flowchart 1300. In other words, PM transmitter 1400 is the structural embodiment for performing the operational steps of flowchart 1300. However, it should be understood that the scope and spirit of the present invention includes other structural embodiments for performing the steps of flowchart 1300. The specifics of these other structural embodiments will be apparent to persons skilled in the relevant art(s) based on the discussion contained herein.
The operation of the transmitter 1400 will now be described in detail with reference to the flowchart 1300. In step 1302, an information signal 1402 (for example, see
In this embodiment, an information signal is accepted and a modulated signal whose amplitude varies as a function of the information signal is transmitted.
3.2.3.1 Operational Description.
The flow chart of
In step 1502, an information signal 4502 (
An oscillating signal 4504 (
As stated before, a harmonically rich signal 4506, such as the rectangular wave as indicated in block 1514, has sinusoidal components (harmonics) at frequencies that are integer multiples of the fundamental frequency of the underlying waveform (the Fourier component frequencies). The first three harmonic waveforms are shown in
The EM signal is prepared for transmission in step 1520, and in step 1522, the EM signal is transmitted.
3.2.3.2 Structural Description.
Preferably, the local oscillator 1610, summing module 1606, switch module 1614, filter 1618, and transmission module 1622 process an information signal 1602 in the manner shown in the operational flowchart 1500. In other words, AM transmitter 1600 is the structural embodiment for performing the operational steps of flowchart 1500. However, it should be understood that the scope and spirit of the present invention includes other structural embodiments for performing the steps of flowchart 1500. The specifics of these other structural embodiments will be apparent to persons skilled in the relevant art(s) based on the discussion contained herein.
The operation of the transmitter 1600 will now be described in detail with reference to the flowchart 1500. In step 1502, information signal 1602 (for example, see
Note that the description of the AM embodiment given herein shows the information signal being gated, thus applying the amplitude modulation to the harmonically rich signal. However, is would be apparent based on the teachings contained herein, that the information signal can be modulated onto the harmonically rich signal or onto a filtered harmonic at any point in the circuit.
3.2.4 Fourth Embodiment In-Phase/Quadrature-Phase Modulation (“I/Q”) ModeIn-phase/quadrature-phase modulation (“I/Q”) is a specific subset of a phase modulation (PM) embodiment. Because “I/Q” is so pervasive, it is described herein as a separate embodiment. However, it should be remembered that since it is a specific subset of PM, the characteristics of PM also apply to “I/Q.”
In this embodiment, two information signals are accepted. An in-phase signal (“I”) is modulated such that its phase varies as a function of one of the information signals, and a quadrature-phase signal (“Q”) is modulated such that its phase varies as a function of the other information signal. The two modulated signals are combined to form an “I/Q” modulated signal and transmitted.
3.2.4.1 Operational Description.
The flow chart of
In step 1714, a second information signal is generated. Again, this signal may be analog, digital, or any combination thereof, and may be different than the first information signal. In step 1712, the phase of “I” oscillating signal generated in step 1710 is shifted, creating a quadrature-phase oscillating signal (referred to as the “Q” signal). In step 1716, the “Q” signal is modulated by the second information signal. This results in the “Q” modulated signal as indicated in block 1718 wherein the phase of the “Q” modulated signal is varied as a function of the second information signal.
An “I” signal with a continuous periodic waveform is generated at step 1708 using the “I” modulated signal, and a “Q” signal with a continuous periodic waveform is generated at step 1720 using the “Q” modulated signal. In step 1722, the “I” periodic waveform and the “Q” periodic waveform are combined forming what is referred to as the “I/Q” periodic waveform as indicated in block 1724. As stated before, a continuous and periodic waveform, such as a “I/Q” rectangular wave as indicated in block 1724, has sinusoidal components (harmonics) at frequencies that are integer multiples of the fundamental frequency of the underlying waveform (the Fourier component frequencies). In step 1726, the unwanted frequencies are removed, and as indicated in block 1728, the remaining frequency is at the desired EM output.
The “VQ” EM signal is prepared for transmission in step 1730, and in step 1732, the “I/Q” EM signal is transmitted.
3.2.4.2 Structural Description.
Preferably, the local oscillator 1806, phase shifter 1810, phase modulators 1804 & 1816, switch modules 1822 & 1828, summer 1832, filter 1836, and transmission module 1840 process the information signal in the manner shown in the operational flowchart 1700. In other words, “I/Q” transmitter 1800 is the structural embodiment for performing the operational steps of flowchart 1700. However, it should be understood that the scope and spirit of the present invention includes other structural embodiments for performing the steps of flowchart 1700. The specifics of these other structural embodiments will be apparent to persons skilled in the relevant art(s) based on the discussion contained herein.
The operation of the transmitter 1800 will now be described in detail with reference to the flowchart 1700 In step 1702, a first information signal 1802 from a source (not shown) is routed to the first phase modulator 1804. In step 1710, an “I” oscillating signal 1808 from local oscillator 1806 is generated and in step 1704, “I” oscillating signal 1808 is modulated by first information signal 1802 in the first phase modulator 1804, thereby producing an “I” modulated signal 1820. In step 1708, the first switch module 1822 generates a harmonically rich “I” signal 1824 with a continuous and periodic waveform.
In step 1714, a second information signal 1814 from a source (not shown) is routed to the second phase modulator 1816. In step 1712, the phase of oscillating signal 1808 is shifted by phase shifter 1810 to create “Q” oscillating signal 1812. In step 1716, “Q” oscillating signal 1812 is modulated by second information signal 1814 in the second phase modulator 1816, thereby producing “Q” modulated signal 1826. In step 1720, the second switch module 1828 generates a harmonically rich “Q” signal 1830 with a continuous and periodic waveform. Harmonically rich “I” signal 1824 and harmonically rich “Q” signal 1830 are preferably rectangular waves, such as square waves or pulses (although, the invention is not limited to this embodiment), and are comprised of pluralities of sinusoidal waves whose frequencies are integer multiples of the fundamental frequency of the waveforms. These sinusoidal waves are referred to as the harmonics of the underlying waveforms, and a Fourier analysis will determine the amplitude of each harmonic.
In step 1722, harmonically rich “I” signal 1824 and harmonically rich “Q” signal 1830 are combined by summer 1832 to create harmonically rich “I/Q” signal 1834. In step 1726, a filter 1836 filters out the undesired harmonic frequencies, and outputs an “I/Q” electromagnetic (EM) signal 1838 at the desired harmonic frequency. In step 1730, “I/Q” EM signal 1838 is routed to transmission module 1840 (optional), where it is prepared for transmission. In step 1732, the transmission module 1840 outputs a transmitted signal 1842.
It will be apparent to those skilled in the relevant art(s) that an alternate embodiment exists wherein the harmonically rich “I” signal 1824 and the harmonically rich “Q” signal 1830 may be filtered before they are summed, and further, another alternate embodiment exists wherein “I” modulated signal 1820 and “Q” modulated signal 1826 may be summed to create an “I/Q” modulated signal before being routed to a switch module.
3.2.5 Other EmbodimentsOther embodiments of the up-converter of the present invention being used as a transmitter (or in other applications) may use subsets and combinations of modulation techniques, and may include modulating one or more information signals as part of the up-conversion process.
3.2.5.1 Combination of Modulation Techniques
Combinations of modulation techniques that would be apparent to those skilled in the relevant art(s) based on the teachings disclosed herein include, but are not limited to, quadrature amplitude modulation (QAM), and embedding two forms of modulation onto a signal for up-conversion.
An exemplary circuit diagram illustrating the combination of two modulations is found in
The embodiments described above are provided for purposes of illustration. These embodiments are not intended to limit the invention. Alternate embodiments, differing slightly or substantially from those described herein, will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such alternate embodiments include, but are not limited to, combinations of modulation techniques in an “I/Q” mode. Such alternate embodiments fall within the scope and spirit of the present invention.
3.2.5.2 Modulation as Part of the Up-Conversion Process.
Alternate embodiments of the present invention include implementations wherein one or more information signals are modulated as part of the up-conversion process. For ease of discussion, these implementations will be referred to as “modulation embodiments” and will be discussed in more detail below.
In a first modulation embodiment, one information signal is phase modulated onto the carrier signal as part of the up-conversion process. Two exemplary implementations of this modulation embodiment are herein described. One involves using a differentiation circuit and the other involves using parallel switches that are controlled by signals that are 180° out of phase with each other.
In a second modulation embodiment, two information signals are multiplied. As part of the up-conversion process, one signal is phase modulated onto the carrier and the other signal is amplitude modulated onto the carrier. Again, as described in the first modulation embodiment above, two exemplary implementations of this modulation embodiment are herein described.
In a third modulation embodiment, one information signal is phase modulated onto the “I” phase of the carrier signal as part of the up-conversion process and a second information signal is phase modulated onto the “Q” phase of the carrier as part of the up-conversion process. As described above, two exemplary implementations of this modulation embodiment are herein described.
In a fourth modulation embodiment, a first information signal is multiplied with a second information signal, and the result is modulated onto the “I” phase of a carrier as part of the up-conversion process. The first information signal is phase modulated and the second information signal is amplitude modulated. Additionally, a third information signal is multiplied with a fourth information signal, and the result is modulated onto the “Q” phase of a carrier as part of the up-conversion process. The third information signal is phased modulated and the fourth information signal is amplitude modulated. As described above, two exemplary implementations of this modulation embodiment are herein described.
It is noted that the exemplary implementations are described herein for illustrative purposes only. The invention is not limited to these examples. Other implementations will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein.
One exemplary implementation of the first modulation embodiment is shown in
A local oscillator 6508 generates an oscillating signal 6526. The frequency of oscillating signal 6526 is a sub-harmonic of the desired output frequency of the up-converter. Oscillating signal 6526 is routed through a pulse shaper 6510. Pulse shaper 6510 is optional, and, when used, outputs a string of pulses 6528. String of pulses 6528 is connected to the control input of switch 6512, and controls the frequency at which switch 6512 closes and opens.
The first input of switch 6512 is also connected to the input of a differentiation circuit 6516. Differentiation circuit 6516 is shown as being comprised of a capacitor 6518 in series and a resistor 6520 shunted to ground. This circuit diagram is shown for illustrative purposes only, and persons skilled in the relevant art(s) will appreciate that other differentiating circuits may be used. The output of differentiation circuit 6516 is a harmonically rich signal 6524 that is phase modulated. Harmonically rich signal 6524 is comprised of a plurality of harmonics and is routed to a filter 6530. Filter 6530 extracts one or more of the harmonics as desired output signal 6532.
A second exemplary implementation of the first modulation embodiment is shown in
Buffered information signal 6710 is then routed through a load, shown as an inductor 6730, to the first input of a switch 6726, and inverted information signal 6712 is routed through a load, shown as an inductor 6732, to the first input of a switch 6728. The second input of switch 6726 and the second input of switch 6728 are connected to a reference 6746. As shown in
A local oscillator 6714 generates an oscillating signal 6716. The frequency of oscillating signal 6716 is preferably an odd sub-harmonic of the desired output frequency of the up-converter. Oscillating signal 6716 is routed through a 180° phase shifter 6718 to generate a phase shifted oscillating signal 6720. Oscillating signal 6716 is also routed through a pulse shaper 6722, and phase shifted oscillating signal 6720 is routed through a pulse shaper 6724. Pulse shaper 6722 and pulse shaper 6724 are both optional, and, when used, output a string of pulses 6748 and a string of pulses 6750, respectively. String of pulses 6748 is connected to the control input of switch 6726 and controls the frequency at which switch 6726 closes and opens. String of pulses 6750 is connected to the control input of switch 6728 and controls the frequency at which switch 6728 closes and opens.
A signal 6734 from the first input of switch 6726 and a signal 6736 from the first input of switch 6728 are combined by a summer 6738. The output of summer 6738 is a harmonically rich signal 6740 that is phase modulated. Harmonically rich signal 6740 is comprised of a plurality of harmonics and is routed to a filter 6742. Filter 6742 extracts one or more of the harmonics as desired output signal 6744.
One exemplary implementation of the second modulation embodiment of the present invention is shown in
Combined signal 6608 is routed through an optional filter 6610. This results in a filtered combined signal 6612. Filtered combined signal 6612 is connected through a load, shown as an inductor 6614, to the first input of a switch 6616. The second input of switch 6616 is connected to a reference 6626. Preferably, reference 6626 is at the potential about which first information signal 6602 switches. That is, if first information signal 6602 is a digital signal whose “low” value is 0 volts and whose “high” value is 5 volts, then reference 6626 will be between 0 and 5 volts, such as, for example, 2.5 volts. This example is for illustrative purposes only, and is not meant to be limiting. A person skilled in the relevant art(s) will understand that there are a number of values for the “high,” “low,” and reference voltages which will result in a phase shift of the carrier when the “state” of the information signal crosses the reference voltage.
A local oscillator 6618 generates an oscillating signal 6620. The frequency of oscillating signal 6620 is a sub-harmonic of the desired output frequency of the up-converter. Oscillating signal 6620 is routed through a pulse shaper 6622. Pulse shaper 6622 is optional, and, when used, outputs a string of pulses 6624. String of pulses 6624 is connected to the control input of switch 6616, and controls the frequency at which switch 6616 closes and opens.
The first input of switch 6616 is also connected to the input of a differentiation circuit 6628. In
Harmonically rich signal 6634 is comprised of a plurality of harmonics and is routed to a filter 6636. Filter 6636 extracts one or more of the harmonics as desired output signal 6638.
Although the discussion herein was directed toward a digital and an analog signal, the invention is not limited to this implementation. The output of differentiation circuit 6628 is such that the phase modulation is a function of an information signal whose high and low states are above and below the reference voltage, and the amplitude modulation is a function of the information signal whose voltage remains either above or below the reference voltage, but does not cross it.
A second exemplary implementation of the second modulation embodiment is shown in
Combined signal 6808 is routed through an optional filter 6810. This results in a filtered combined signal 6812. Filtered combined signal 6812 is connected to a buffer/inverter module 6814. Buffer/inverter module 6814 outputs a buffered combined signal 6820 and an inverted combined signal 6822. Buffered combined signal 6820 is substantially the same as filtered combined signal 6812 and inverted combined signal 6822 is substantially equal to the inverse of buffered combined signal 6820. A number of circuits, such as off-the-shelf buffers and off-the-shelf inverters, or custom designed buffers and inverters, can be used to accomplish the function of buffer/inverter module 6814, as can be appreciated by those skilled in the relevant art(s).
Buffered combined signal 6820 is then routed through a load, shown as an inductor 6840, to the first input of a switch 6844, and inverted combined signal 6822 is routed through a load, shown as an inductor 6842, to the first input of a switch 6846. The second input of switch 6844 and the second input of switch 6846 are connected to a reference 6848. As shown in
A local oscillator 6824 generates an oscillating signal 6826. The frequency of oscillating signal 6826 is preferably an odd sub-harmonic of the desired output frequency of the up-converter. Oscillating signal 6826 is routed through a 180° phase shifter 6828 to generate a phase shifted oscillating signal 6830. Oscillating signal 6826 is also routed through a pulse shaper 6832, and phase shifted oscillating signal 6830 is routed through a pulse shaper 6834. Pulse shaper 6832 and pulse shaper 6834 are both optional, and, when used, output a string of pulses 6836 and a string of pulses 6838, respectively. String of pulses 6836 is connected to the control input of switch 6844 and controls the frequency at which switch 6844 closes and opens. String of pulses 6838 is connected to the control input of switch 6846 and controls the frequency at which switch 6846 closes and opens.
A signal 6850 from the first input of switch 6844 and a signal 6852 from the first input of switch 6846 are combined by a summer 6854. The output of summer 6854 is a harmonically rich signal 6856 that is both phase and amplitude modulated. In summary, first information signal 6802, the digital signal, phase modulates harmonically rich signal 6854, and second information signal 6804, the analog signal, amplitude modulates harmonically rich signal 6856.
Harmonically rich signal 6856 is comprised of a plurality of harmonics and is routed to a filter 6858. Filter 6858 extracts one or more of the harmonics as desired output signal 6860.
Although the discussion herein was directed toward a digital and an analog signal, the invention is not limited to this implementation. The output of the circuit is such that the phase modulation is a function of an information signal whose high and low states are above and below the reference voltage, and the amplitude modulation is a function of the information signal whose voltage remains either above or below the reference voltage, but does not cross it. Thus the amplitude is preserved.
One exemplary implementation of the third modulation embodiment is the “I/Q” embodiment shown in
A second information signal 6904 is routed through an optional filter 6908. This results in a second filtered information signal 6912. Typically, second information signal 6904 (as well as second filtered information signal 6912) is a digital signal, although the invention may operate with analog signals. Second filtered information signal 6912 is connected through a load, shown as an inductor 6916, to the first input of a switch 6936. The second input of switch 6936 is connected to a reference 6940. In one implementation, reference 6940 is at ground and, in another implementation, reference 6940 is at a non-zero voltage.
A local oscillator 6918 generates an in-phase, “I,” oscillating signal 6920. The frequency of “I” oscillating signal 6920 is a sub-harmonic of the desired output frequency of the up-converter. “I” oscillating signal 6920 is routed through a pulse shaper 6926. Pulse shaper 6926 is optional, and, when used, outputs an “I” string of pulses 6930. “I” string of pulses 6930 is connected to the control input of switch 6934, and controls the frequency at which switch 6934 closes and opens.
“I” oscillating signal 6920 is also routed through a 90° phase shifter 6922. The output of 90° phase shifter 6922 is a quadrature-phase, “Q,” oscillating signal 6924. “Q” oscillating signal 6924 is routed through a pulse shaper 6928. Pulse shaper 6928 is optional, and, when used, outputs a “Q” string of pulses 6932. “Q” string of pulses 6932 is connected to the control input of switch 6936, and controls the frequency at which switch 6936 closes and opens.
The first input of switch 6934 is also connected to the input of a differentiation circuit 6942. In
The first input of switch 6936 is also connected to the input of a differentiation circuit 6948. In
A second exemplary implementation of the third modulation embodiment is the “I/Q” embodiment shown in
Buffered first information signal 7016 is then routed through a load, shown as an inductor 7066, to the first input of a switch 7074, and inverted first information signal 7018 is routed through a load, shown as an inductor 7068, to the first input of a switch 7076. The second input of switch 7074 and the second input of switch 7076 are connected to a reference 7082. As shown in
A second information signal 7004 is routed to an optional filter 7036. This results in a second filtered information signal 7038. Typically, second information signal 7004 (as well as second filtered information signal 7038) is a digital signal. Second filtered information signal 7038 is connected to a second buffer/inverter module 7040. Second buffer/inverter module 7040 outputs a buffered second information signal 7046 and an inverted second information signal 7048. Buffered second information signal 7046 is substantially the same as second filtered information signal 7038 and inverted second information signal 7048 is substantially equal to the inverse of buffered second information signal 7046. A number of circuits, such as off-the-shelf buffers and off-the-shelf inverters, or custom designed buffers and inverters, can be used to accomplish the function of buffer/inverter module 7040, as can be appreciated by those skilled in the relevant art(s).
Buffered second information signal 7046 is then routed through a load, shown as an inductor 7070, to the first input of a switch 7078, and inverted second information signal 7048 is routed through a load, shown as an inductor 7072, to the first input of a switch 7080. The second input of switch 7078 and the second input of switch 7080 are connected to a reference 7084. As shown in
A local oscillator 7020 generates an in-phase, “I,” oscillating signal 7022. The frequency of “I” oscillating signal 7022 is preferably an odd sub-harmonic of the desired output frequency of the up-converter. “I” oscillating signal 7022 is routed through a 180° phase shifter 7024 to generate a 180° phase shifted “I” oscillating signal 7026. “I” oscillating signal 7022 is also routed through a pulse shaper 7028, and 180° phase shifted “I” oscillating signal 7026 is routed through a pulse shaper 7030. Pulse shaper 7028 and pulse shaper 7030 are both optional, and, when used, output an “I” string of pulses 7032 and an “I” string of pulses 7034, respectively. “I” string of pulses 7032 is connected to the control input of switch 7074 and controls the frequency at which switch 7074 closes and opens. “I” string of pulses 7034 is connected to the control input of switch 7076 and controls the frequency at which switch 7076 closes and opens.
An “I” signal 7086 from the first input of switch 7074 and an “I” signal 7088 from the first input of switch 7076 are combined by a summer 7094. The output of summer 7094 is a harmonically rich “I” signal 7081 that is phase modulated.
“I” oscillating signal 7022 is also routed through a 90° phase shifter 7050 to generate a quadrature-phase, “Q,” oscillating signal 7052. “Q” oscillating signal 7052 is routed through a 180° phase shifter 7054 to generate a 180° phase shifted “Q” oscillating signal 7056. “Q” oscillating signal 7052 is also routed through a pulse shaper 7058, and 180° phase shifted “Q” oscillating signal 7056 is routed through a pulse shaper 7060. Pulse shaper 7058 and pulse shaper 7060 are both optional, and, when used, output a “Q” string of pulses 7062 and a “Q” string of pulses 7064, respectively. “Q” string of pulses 7062 is connected to the control input of switch 7078 and controls the frequency at which switch 7078 closes and opens. “Q” string of pulses 7064 is connected to the control input of switch 7080 and controls the frequency at which switch 7080 closes and opens.
A “Q” signal 7090 from the first input of switch 7078 and a “Q” signal 7092 from the first input of switch 7080 are combined by a summer 7096. The output of summer 7096 is a harmonically rich “Q” signal 7083 that is phase modulated.
Harmonically rich “I” signal 7081 and harmonically rich “Q” signal 7083 are combined by summer 7085 which outputs a harmonically rich “I/Q” signal 7087. Harmonically rich “I/Q” signal 7087 is comprised of a plurality of harmonics and is routed to a filter 7089. Filter 7089 extracts one or more of the harmonics as desired “I/Q” output signal 7098.
In the fourth modulation embodiment, four information signals are modulated onto an “I/Q” carrier as shown in the example of
A local oscillator 7114 generates an in-phase, “I,” oscillating signal 7116. The frequency of “I” oscillating signal 7116 is a sub-harmonic frequency of the desired output frequency of the up-converter, and is received by multiplication, modulation, and harmonic generation module 7110, and causes it to output a harmonically rich “I” signal 7122 that is both phase and amplitude modulated. In the exemplary implementation wherein the multiplication, modulation, and harmonic generation module 7110 is multiplication, modulation, and harmonic generation module 6800, the frequency of “I” oscillating signal 7116 is an odd sub-harmonic of the desired output frequency.
A third information signal 7106 and a fourth information signal 7108 are received by a multiplication, modulation, and harmonic generation module 7112. A first exemplary implementation of multiplication, modulation, and harmonic generation module 7112 is shown in
“I” oscillating signal 7116 is routed to 90° phase shifter 7118. The output of 90° phase shifter 7118 is a quadrature-phase, “Q,” oscillating signal 7120. “Q” oscillating signal 7120 is received by multiplication, modulation, and harmonic generation module 7112 and causes it to output a harmonically rich “Q” signal 7124 that is both phase and amplitude modulated.
Harmonically rich “I” signal 7122 and harmonically rich “Q” signal 7124 are combined by a summer 7126. The output of summer 7126 is a harmonically rich “I/Q” signal 7128. Harmonically rich “I/Q” signal 7128 is comprised of a plurality of harmonics and is routed to a filter 7130. Filter 7130 extracts one or more of the harmonics as desired “I/Q” output signal 7132. Desired “I/Q” output signal 7132 is phase and amplitude modulated on the “I” phase and phase and amplitude modulated on the “Q” phase, as discussed above in the discussion of the second modulation embodiment.
3.3 Methods and Systems for Implementing the EmbodimentsExemplary operational and/or structural implementations related to the method(s), structure(s), and/or embodiments described above are presented in this section (and its subsections). These components and methods are presented herein for purposes of illustration, and not limitation. The invention is not limited to the particular examples of components and methods described herein. Alternatives (including equivalents, extensions, variations, deviations, etc., of those described herein) will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such alternatives fall within the scope and spirit of the present invention.
3.3.1 The Voltage Controlled Oscillator (FM Mode).
As discussed above, the frequency modulation (FM) mode embodiment of the invention uses a voltage controlled oscillator (VCO). See, as an example, VCO 1204 in
3.3.1.1 Operational Description.
The information signal 2302 is accepted and an oscillating signal 2306 whose frequency varies as a function of the information signal 2302 is created. Oscillating signal 2306 is also referred to as frequency modulated intermediate signal 2306. The information signal 2302 may be analog or digital or a combination thereof, and may be conditioned to ensure it is within the desired range.
In the case where the information signal 2302 is digital, the oscillating signal 2306 may vary between discrete frequencies. For example, in a binary system, a first frequency corresponds to a digital “high,” and a second frequency corresponds to a digital “low.” Either frequency may correspond to the “high” or the “low,” depending on the convention being used. This operation is referred to as frequency shift keying (FSK) which is a subset of FM. If the information signal 2302 is analog, the frequency of the oscillating signal 2306 will vary as a function of that analog signal, and is not limited to the subset of FSK described above.
The oscillating signal 2306 is a frequency modulated signal which can be a sinusoidal wave, a rectangular wave, a triangular wave, a pulse, or any other continuous and periodic waveform. As stated above, one skilled in the relevant art(s) will recognize the physical limitations to and mathematical obstacles against achieving exact or perfect waveforms and it is not the intent of the present invention that a perfect waveform be generated or needed. Again, as stated above, for ease of discussion, the term “rectangular waveform” will be used to refer to waveforms that are substantially rectangular, the term “square wave” will refer to those waveforms that are substantially square, the term “triangular wave” will refer to those waveforms that are substantially triangular, and the term “pulse” will refer to those waveforms that are substantially a pulse, and it is not the intent of the present invention that a perfect square wave, triangle wave, or pulse be generated or needed.
3.3.1.2 Structural Description.
The design and use of a voltage controlled oscillator 2304 is well known to those skilled in the relevant art(s). The VCO 2304 may be designed and fabricated from discrete components, or it may be purchased “off the shelf.” VCO 2304 accepts an information signal 2302 from a source. The information signal 2302 is at baseband and generally is an electrical signal within a prescribed voltage range. If the information is digital, the voltage will be at discrete levels. If the information is analog, the voltage will be continuously variable between an upper and a lower level. The VCO 2304 uses the voltage of the information signal 2302 to cause a modulated oscillating signal 2306 to be output. The information signal 2302, because it is a baseband signal and is used to modulate the oscillating signal, may be referred to as the modulating baseband signal 2302.
The frequency of the oscillating signal 2306 varies as a function of the voltage of the modulating baseband signal 2302. If the modulating baseband signal 2302 represents digital information, the frequency of the oscillating signal 2306 will be at discrete levels. If, on the other hand, the modulating baseband signal 2302 represents analog information, the frequency of the oscillating signal 2306 will be continuously variable between its higher and lower frequency limits. The oscillating signal 2306 can be a sinusoidal wave, a rectangular wave, a triangular wave, a pulse, or any other continuous and periodic waveform.
The frequency modulated oscillating signal 2306 may then be used to drive a switch module 2802.
3.3.2 The Local Oscillator (PM, AM, and “I/Q” Modes).
As discussed above, the phase modulation (PM) and amplitude modulation (AM) mode embodiments of the invention use a local oscillator. So too does the in-phase/quadrature-phase modulation (“I/Q”) mode embodiment. See, as an example, local oscillator 1406 in
3.3.2.1 Operational Description.
An oscillating signal 2404 is generated. The frequency of the signal 2404 may be selectable, but generally is not considered to be “variable.” That is, the frequency may be selected to be a specific value for a specific implementation, but generally it does not vary as a function of the information signal 2302 (i.e., the modulating baseband signal).
The oscillating signal 2404 generally is a sinusoidal wave, but it may also be a rectangular wave, a triangular wave, a pulse, or any other continuous and periodic waveform. As stated above, one skilled in the relevant art(s) will recognize the physical limitations to and mathematical obstacles against achieving exact or perfect waveforms and it is not the intent of the present invention that a perfect waveform be generated or needed. Again, as stated above, for ease of discussion, the term “rectangular waveform” will be used to refer to waveforms that are substantially rectangular, the term “square wave” will refer to those waveforms that are substantially square, the term “triangular wave” will refer to those waveforms that are substantially triangular, and the term “pulse” will refer to those waveforms that are substantially a pulse, and it is not the intent of the present invention that a perfect square wave, triangle wave, or pulse be generated or needed.
3.3.2.2 Structural Description.
The design and use of a local oscillator 2402 is well known to those skilled in the relevant art(s). A local oscillator 2402 may be designed and fabricated from discrete components or it may be purchased “off the shelf.” A local oscillator 2402 is generally set to output a specific frequency. The output can be “fixed” or it can be “selectable,” based on the design of the circuit. If it is fixed, the output is considered to be substantially a fixed frequency that cannot be changed. If the output frequency is selectable, the design of the circuit will allow a control signal to be applied to the local oscillator 2402 to change the frequency for different applications. However, the output frequency of a local oscillator 2402 is not considered to be “variable” as a function of an information signal 2302 such as the modulating baseband signal 2302. (If it were desired for the output frequency of an oscillator to be variable as a function of an information signal, a VCO would preferably be used.) The oscillating signal 2404 generally is a sinusoidal wave, but it may also be a rectangular wave, a triangular wave, a pulse, or any other continuous and periodic waveform.
The output of a local oscillator 2402 may be an input to other circuit components such as a phase modulator 2606, a phase shifting circuit 2504, switch module 3102, etc.
3.3.3 The Phase Shifter (“I/Q” Mode).
As discussed above, the in-phase/quadrature-phase modulation (“I/Q”) mode embodiment of the invention uses a phase shifter. See, as an example, phase shifter 1810 in
3.3.3.1 Operational Description.
An “in-phase” oscillating signal 2502 is received and a “quadrature-phase” oscillating signal 2506 is output. If the in-phase (“I”) signal 2502 is referred to as being a sine wave, then the quadrature-phase (“Q”) signal 2506 can be referred to as being a cosine wave (i.e., the “Q” signal 2506 is 90° out of phase with the “I” signal 2502). However, they may also be rectangular waves, triangular waves, pulses, or any other continuous and periodic waveforms. As stated above, one skilled in the relevant art(s) will recognize the physical limitations to and mathematical obstacles against achieving exact or perfect waveforms and it is not the intent of the present invention that a perfect waveform be generated or needed. Again, as stated above, for ease of discussion, the term “rectangular waveform” will be used to refer to waveforms that are substantially rectangular, the term “square wave” will refer to those waveforms that are substantially square, the term “triangular wave” will refer to those waveforms that are substantially triangular, and the term “pulse” will refer to those waveforms that are substantially a pulse, and it is not the intent of the present invention that a perfect square wave, triangle wave, or pulse be generated or needed. Regardless of the shapes of the waveforms, the “Q” signal 2506 is out of phase with the “I” signal 2506 by one-quarter period of the waveform. The frequency of the “I” and “Q” signals 2502 and 2506 are substantially equal.
The discussion contained herein will be confined to the more prevalent embodiment wherein there are two intermediate signals separated by 90°. This is not limiting on the invention. It will be apparent to those skilled in the relevant art(s) that the techniques tough herein and applied to the “I/Q” embodiment of the present invention also apply to more exotic embodiments wherein the intermediate signals are shifted by some amount other than 90°, and also wherein there may be more than two intermediate frequencies.
3.3.3.2 Structural Description.
The design and use of a phase shifter 2504 is well known to those skilled in the relevant art(s). A phase shifter 2504 may be designed and fabricated from discrete components or it may be purchased “off the shelf.” A phase shifter accepts an “in-phase” (“I”) oscillating signal 2502 from any of a number of sources, such as a VCO 2304 or a local oscillator 2402, and outputs a “quadrature-phase” (“Q”) oscillating signal 2506 that is substantially the same frequency and substantially the same shape as the incoming “I” signal 2502, but with the phase shifted by 90°. Both the “I” and “Q” signals 2502 and 2506 are generally sinusoidal waves, but they may also be rectangular waves, triangular waves, pulses, or any other continuous and periodic waveforms. Regardless of the shapes of the waveforms, the “Q” signal 2506 is out of phase with the “I” signal 2502 by one-quarter period of the waveform. Both the “I” and “Q” signals 2502 and 2506 may be modulated.
The output of a phase shifter 2504 may be used as an input to a phase modulator 2606.
3.3.4 The Phase Modulator (PM and “I/Q” Modes).
As discussed above, the phase modulation (PM) mode embodiment including the in-phase/quadrature-phase modulation (“I/Q”) mode embodiment of the invention uses a phase modulator. See, as an example, phase modulator 1404 of
3.3.4.1 Operational Description.
An information signal 2602 and an oscillating signal 2604 are accepted, and a phase modulated oscillating signal 2608 whose phase varies as a function of the information signal 2602 is output. The information signal 2602 may be analog or digital and may be conditioned to ensure it is within the desired range. The oscillating signal 2604 can be a sinusoidal wave, a rectangular wave, a triangular wave, a pulse, or any other continuous and periodic waveform. As stated above, one skilled in the relevant art(s) will recognize the physical limitations to and mathematical obstacles against achieving exact or perfect waveforms and it is not the intent of the present invention that a perfect waveform be generated or needed. Again, as stated above, for ease of discussion, the term “rectangular waveform” will be used to refer to waveforms that are substantially rectangular, the term “square wave” will refer to those waveforms that are substantially square, the term “triangular wave” will refer to those waveforms that are substantially triangular, and the term “pulse” will refer to those waveforms that are substantially a pulse, and it is not the intent of the present invention that a perfect square wave, triangle wave, or pulse be generated or needed. The modulated oscillating signal 2608 is also referred to as the modulated intermediate signal 2608.
In the case where the information signal 2602 is digital, the modulated intermediate signal 2608 will shift phase between discrete values, the first phase (e.g., for a signal represented by sin(ωt+θo)) corresponding to a digital “high,” and the second phase (e.g., for a signal represented by sin(ωt+θo+δ), where δ represents the amount the phase has been shifted) corresponding to a digital “low.” Either phase may correspond to the “high” or the “low,” depending on the convention being used. This operation is referred to as phase shift keying (PSK) which is a subset of PM.
If the information signal 2602 is analog, the phase of the modulated intermediate signal 2608 will vary as a function of the information signal 2602 and is not limited to the subset of PSK described above.
The modulated intermediate signal 2608 is a phase modulated signal which can be a sinusoidal wave, a rectangular wave, a triangular wave, a pulse, or any other continuous and periodic waveform, and which has substantially the same period as the oscillating signal 2604.
3.3.4.2 Structural Description.
The design and use of a phase modulator 2606 is well known to those skilled in the relevant art(s). A phase modulator 2606 may be designed and fabricated from discrete components, or it may be purchased “off the shelf.” A phase modulator 2606 accepts an information signal 2602 from a source and an oscillating signal 2604 from a local oscillator 2402 or a phase shifter 2504. The information signal 2602 is at baseband and is generally an electrical signal within a prescribed voltage range. If the information is digital, the voltage will be at discrete levels. If the information is analog, the voltage will be continuously variable between an upper and a lower level as a function of the information signal 2602. The phase modulator 2606 uses the voltage of the information signal 2602 to modulate the oscillating signal 2604 and causes a modulated intermediate signal 2608 to be output. The information signal 2602, because it is a baseband signal and is used to modulate the oscillating signal, may be referred to as the modulating baseband signal 2604.
The modulated intermediate signal 2608 is an oscillating signal whose phase varies as a function of the voltage of the modulating baseband signal 2602. If the modulating baseband signal 2602 represents digital information, the phase of the modulated intermediate signal 2608 will shift by a discrete amount (e.g., the modulated intermediate signal 2608 will shift by an amount δ between sin(ωt+θo) and sin(ωt+θo+δ)). If, on the other hand, the modulating baseband signal 2602 represents analog information, the phase of the modulated intermediate signal 2608 will continuously shift between its higher and lower phase limits as a function of the information signal 2602. In one exemplary embodiment, the upper and lower limits of the modulated intermediate signal 2608 can be represented as sin(ωt+θo) and sin(ωt+θo+π). In other embodiments, the range of the phase shift may be less than π. The modulated intermediate signal 2608 can be a sinusoidal wave, a rectangular wave, a triangular wave, a pulse, or any other continuous and periodic waveform.
The phase modulated intermediate signal 2608 may then be used to drive a switch module 2802.
3.3.5 The Summing Module (AM Mode).
As discussed above, the amplitude modulation (AM) mode embodiment of the invention uses a summing module. See, as an example, summing module 1606 in
3.3.5.1 Operational Description.
An information signal 2702 and a bias signal 2702 are accepted, and a reference signal is output. The information signal 2702 may be analog or digital and may be conditioned to ensure it is within the proper range so as not to damage any of the circuit components. The bias signal 2704 is usually a direct current (DC) signal.
In the case where the information signal 2702 is digital, the reference signal 2706 shifts between discrete values, the first value corresponding to a digital “high,” and the second value corresponding to a digital “low.” Either value may correspond to the “high” or the “low,” depending on the convention being used. This operation is referred to as amplitude shift keying (ASK) which is a subset of AM.
If the information signal 2702 is analog, the value of the reference signal 2708 will vary linearly between upper and lower extremes which correspond to the upper and lower limits of the information signal 2702. Again, either extreme of the reference signal 2708 range may correspond to the upper or lower limit of the information signal 2702 depending on the convention being used.
The reference signal 2708 is a digital or analog signal and is substantially proportional to the information signal 2702.
3.3.5.2 Structural Description.
The design and use of a summing module 2706 is well known to those skilled in the relevant art(s). A summing module 2706 may be designed and fabricated from discrete components, or it may be purchased “off the shelf” A summing module 2706 accepts an information signal 2702 from a source. The information signal 2702 is at baseband and generally is an electrical signal within a prescribed voltage range. If the information is digital, the information signal 2702 is at either of two discrete levels. If the information is analog, the information signal 2702 is continuously variable between an upper and a lower level. The summing module 2706 uses the voltage of the information signal 2702 and combines it with a bias signal 2704. The output of the summing module 2706 is called the reference signal 2708. The purpose of the summing module 2706 is to cause the reference signal 2708 to be within a desired signal range. One skilled in the relevant art(s) will recognize that the information signal 2702 may be used directly, without being summed with a bias signal 2704, if it is already within the desired range. The information signal 2702 is a baseband signal, but typically, in an AM embodiment, it is not used to directly modulate an oscillating signal. The amplitude of the reference signal 2708 is at discrete levels if the information signal 2702 represents digital information. On the other hand, the amplitude of the reference signal 2708 is continuously variable between its higher and lower limits if the information signal 2702 represents analog information. The amplitude of the reference signal 2708 is substantially proportional to the information signal 2702, however, a positive reference signal 2708 need not represent a positive information signal 2702.
The reference signal 2708 is routed to the first input 3108 of a switch module 3102. In one exemplary embodiment, a resistor 2824 is connected between the output of the summing module 2706 (or the source of the information signal 2702 in the embodiment wherein the summing amplifier 2706 is not used) and the switch 3116 of the switch module 3102.
3.3.6 The Switch Module (FM, PM, and “I/Q” Modes).
As discussed above, the frequency modulation (FM), phase modulation (PM), and the in-phase/quadrature-phase modulation (“I/Q”) mode embodiments of the invention use a switching assembly referred to as switch module 2802 (
3.3.6.1 Operational Description.
A bias signal 2806 is gated as a result of the application of a modulated oscillating signal 2804, and a signal with a harmonically rich waveform 2814 is created. The bias signal 2806 is generally a fixed voltage. The modulated oscillating signal 2804 can be frequency modulated, phase modulated, or any other modulation scheme or combination thereof. In certain embodiments, such as in certain amplitude shift keying modes, the modulated oscillating signal 2804 may also be amplitude modulated. The modulated oscillating signal 2804 can be a sinusoidal wave, a rectangular wave, a triangular wave, a pulse, or any other continuous and periodic waveform. In a preferred embodiment, modulated oscillating signal 2804 would be a rectangular wave. As stated above, one skilled in the relevant art(s) will recognize the physical limitations to and mathematical obstacles against achieving exact or perfect waveforms and it is not the intent of the present invention that a perfect waveform be generated or needed. Again, as stated above, for ease of discussion, the term “rectangular waveform” will be used to refer to waveforms that are substantially rectangular, the term “square wave” will refer to those waveforms that are substantially square, the term “triangular wave” will refer to those waveforms that are substantially triangular, and the term “pulse” will refer to those waveforms that are substantially a pulse, and it is not the intent of the present invention that a perfect square wave, triangle wave, or pulse be generated or needed.
The signal with harmonically rich waveform 2814, hereafter referred to as the harmonically rich signal 2814, is a continuous and periodic waveform that is modulated substantially the same as the modulated oscillating signal 2804. That is, if the modulated oscillating signal 2804 is frequency modulated, the harmonically rich signal 2814 will also be frequency modulated, and if the modulated oscillating signal 2804 is phase modulated, the harmonically rich signal 2814 will also be phase modulated. (In one embodiment, the harmonically rich signal 2814 is a substantially rectangular waveform.) As stated before, a continuous and periodic waveform, such as a rectangular wave, has sinusoidal components (harmonics) at frequencies that are integer multiples of the fundamental frequency of the underlying waveform (the Fourier component frequencies). Thus, the harmonically rich signal 2814 is composed of sinusoidal signals at frequencies that are integer multiples of the fundamental frequency of itself.
3.3.6.2 Structural Description.
The switch module 2802 of an embodiment of the present invention is comprised of a first input 2808, a second input 2810, a control input 2820, an output 2822, and a switch 2816. A bias signal 2806 is applied to the first input 2808 of the switch module 2802. Generally, the bias signal 2806 is a fixed voltage, and in one embodiment of the invention, a resistor 2824 is located between the bias signal 2806 and the switch 2816. The second input 2810 of the switch module 2802 is generally at electrical ground 2812. However, one skilled in the relevant art(s) will recognize that alternative embodiments exist wherein the second input 2810 may not be at electrical ground 2812, but rather a second signal 2818, provided that the second signal 2818 is different than the bias signal 2806.
A modulated oscillating signal 2804 is connected to the control input 2820 of the switch module 2802. The modulated oscillating signal 2804 may be frequency modulated or phase modulated. (In some circumstances and embodiments, it may be amplitude modulated, such as in on/off keying, but this is not the general case, and will not be described herein.) The modulated oscillating signal 2804 can be a sinusoidal wave, a rectangular wave, a triangular wave, a pulse, or any other continuous and periodic waveform. In a preferred embodiment, it would be a rectangular wave. The modulated oscillating signal 2804 causes the switch 2816 to close and open.
The harmonically rich signal 2814 described in section 3.3.6.1 above, is found at the output 2822 of the switch module 2802. The harmonically rich signal 2814 is a continuous and periodic waveform that is modulated substantially the same as the modulated oscillating signal 2804. That is, if the modulated oscillating signal 2804 is frequency modulated, the harmonically rich signal 2814 will also be frequency modulated, and if the modulated oscillating signal 2804 is phase modulated, the harmonically rich signal 2814 will also be phase modulated. In one embodiment, the harmonically rich signal 2814 has a substantially rectangular waveform. As stated before, a continuous and periodic waveform, such as a rectangular wave, has sinusoidal components (harmonics) at frequencies that are integer multiples of the fundamental frequency of the underlying waveform (the Fourier component frequencies). Thus, the harmonically rich signal 2814 is composed of sinusoidal signals at frequencies that are integer multiples of the fundamental frequency of itself. Each of these sinusoidal signals is also modulated substantially the same as the continuous and periodic waveform (i.e., the modulated oscillating signal 2804) from which it is derived.
The switch module 2802 operates as follows. When the switch 2816 is “open,” the output 2822 of switch module 2802 is at substantially the same voltage level as bias signal 2806. Thus, since the harmonically rich signal 2814 is connected directly to the output 2822 of switch module 2802, the amplitude of harmonically rich signal 2814 is equal to the amplitude of the bias signal 2806. When the modulated oscillating signal 2804 causes the switch 2816 to become “closed,” the output 2822 of switch module 2802 becomes connected electrically to the second input 2810 of switch module 2802 (e.g., ground 2812 in one embodiment of the invention), and the amplitude of the harmonically rich signal 2814 becomes equal to the potential present at the second input 2810 (e.g., zero volts for the embodiment wherein the second input 2810 is connected to electrical ground 2812). When the modulated oscillating signal 2804 causes the switch 2816 to again become “open,” the amplitude of the harmonically rich signal 2814 again becomes equal to the bias signal 2806. Thus, the amplitude of the harmonically rich signal 2814 is at either of two signal levels, i.e., bias signal 2806 or ground 2812, and has a frequency that is substantially equal to the frequency of the modulated oscillating signal 2804 that causes the switch 2816 to open and close. The harmonically rich signal 2814 is modulated substantially the same as the modulated oscillating signal 2804. One skilled in the relevant art(s) will recognize that any one of a number of switch designs will fulfill the scope and spirit of the present invention as described herein.
In an embodiment of the invention, the switch 2816 is a semiconductor device, such as a diode ring. In another embodiment, the switch is a transistor, such as a field effect transistor (FET). In an embodiment wherein the FET is gallium arsenide (GaAs), switch module 2802 can be designed as seen in
An alternate implementation of the design includes a “dwell capacitor” wherein one side of a capacitor is connected to the first input of the switch and the other side of the capacitor is connected to the second input of the switch. The purpose of the design is to increase the apparent aperture of the pulse without actually increasing its width. For additional detail on the design and use of a dwell capacitor, see co-pending application entitled “Method and System for Down-Converting Electromagnetic Signals Having Optimized Switch Structures,” Ser. No. 09/293,095, filed Apr. 16, 1999, and other applications as referenced above.
Other switch designs and implementations will be apparent to persons skilled in the relevant art(s).
The output 2822 of the switch module 2802, i.e., the harmonically rich signal 2814, can be routed to a filter 3504 in the FM and PM modes or to a Summer 3402 in the “I/Q” mode.
3.3.7 The Switch Module (AM Mode).
As discussed above, the amplitude modulation (AM) mode embodiment of the invention uses a switching assembly referred to as switch module 3102 (
3.3.7.1 Operational Description.
A reference signal 3106 is gated as a result of the application of an oscillating signal 3104, and a signal with a harmonically rich waveform 3114 is created. The reference signal 3106 is a function of the information signal 2702 and may, for example, be either the summation of the information signal 2702 with a bias signal 2704 or it may be the information signal 2702 by itself. In the AM mode, the oscillating signal 3104 is generally not modulated, but can be.
The oscillating signal 3104 can be a sinusoidal wave, a rectangular wave, a triangular wave, a pulse, or any other continuous and periodic waveform. In a preferred embodiment, it would be a rectangular wave. As stated above, one skilled in the relevant art(s) will recognize the physical limitations to and mathematical obstacles against achieving exact or perfect waveforms and it is not the intent of the present invention that a perfect waveform be generated or needed. Again, as stated above, for ease of discussion, the term “rectangular waveform” will be used to refer to waveforms that are substantially rectangular, the term “square wave” will refer to those waveforms that are substantially square, the term “triangular wave” will refer to those waveforms that are substantially triangular, and the term “pulse” will refer to those waveforms that are substantially a pulse, and it is not the intent of the present invention that a perfect square wave, triangle wave, or pulse be generated or needed.
The signal with a harmonically rich waveform 3114, hereafter referred to as the harmonically rich signal 3114, is a continuous and periodic waveform whose amplitude is a function of the reference signal. That is, it is an AM signal. In one embodiment, the harmonically rich signal 3114 has a substantially rectangular waveform. As stated before, a continuous and periodic waveform, such as a rectangular wave, will have sinusoidal components (harmonics) at frequencies that are integer multiples of the fundamental frequency of the underlying waveform (the Fourier component frequencies). Thus, harmonically rich signal 3114 is composed of sinusoidal signals at frequencies that are integer multiples of the fundamental frequency of itself.
Those skilled in the relevant art(s) will recognize that alternative embodiments exist wherein combinations of modulations (e.g., PM and ASK, FM and AM, etc.) may be employed simultaneously. In these alternate embodiments, the oscillating signal 3104 may be modulated. These alternate embodiments will be apparent to persons skilled in the relevant art(s), and thus will not be described herein.
3.3.7.2 Structural Description.
The switch module 3102 of the present invention is comprised of a first input 3108, a second input 3110, a control input 3120, an output 3122, and a switch 3116. A reference signal 3106 is applied to the first input 3108 of the switch module 3102. Generally, the reference signal 3106 is a function of the information signal 2702, and may either be the summation of the information signal 2702 with a bias signal or it may be the information signal 2702 by itself. In one embodiment of the invention, a resistor 3124 is located between the reference signal 3106 and the switch 3116. The second input 3110 of the switch module 3102 is generally at electrical ground 3112, however, one skilled in the relevant art(s) will recognize that alternative embodiments exist wherein the second input 3110 may not be at electrical ground 3112, but rather connected to a second signal 3118. In an alternate embodiment, the inverted value of the reference signal 3106 is connected to the second input 3110 of the switch module 3102.
An oscillating signal 3104 is connected to the control input 3120 of the switch module 3102. Generally, in the AM mode, the oscillating signal 3104 is not modulated, but a person skilled in the relevant art(s) will recognize that there are embodiments wherein the oscillating signal 3104 may be frequency modulated or phase modulated, but these will not be described herein. The oscillating signal 3104 can be a sinusoidal wave, a rectangular wave, a triangular wave, a pulse, or any other continuous and periodic waveform. In a preferred embodiment, it would be a rectangular wave. The oscillating signal 3104 causes the switch 3116 to close and open.
The harmonically rich signal 3114 described in section 3.3.7.1 above is found at the output 3122 of the switch module 3102. The harmonically rich signal 3114 is a continuous and periodic waveform whose amplitude is a function of the amplitude of the reference signal. In one embodiment, the harmonically rich signal 3114 has a substantially rectangular waveform. As stated before, a continuous and periodic waveform, such as a rectangular wave, has sinusoidal components (harmonics) at frequencies that are integer multiples of the fundamental frequency of the underlying waveform (the Fourier component frequencies). Thus, harmonically rich signal 3114 is composed of sinusoidal signals at frequencies that are integer multiples of the fundamental frequency of itself. As previously described, the relative amplitude of the harmonics of a continuous periodic waveform is generally a function of the ratio of the pulse width of the rectangular wave and the period of the fundamental frequency, and can be determined by doing a Fourier analysis of the periodic waveform. When the amplitude of the periodic waveform varies, as in the AM mode of the invention, the change in amplitude of the periodic waveform has a proportional effect on the absolute amplitude of the harmonics. In other words, the AM is embedded on top of each of the harmonics.
The description of the switch module 3102 is substantially as follows: When the switch 3116 is “open,” the amplitude of the harmonically rich signal 3114 is substantially equal to the reference signal 3106. When the oscillating signal 3104 causes the switch 3116 to become “closed,” the output 3122 of the switch module 3102 becomes connected electrically to the second input 3110 of the switch module 3102 (e.g., ground 3112 in one embodiment), and the amplitude of the harmonically rich signal 3114 becomes equal to the value of the second input 3110 (e.g., zero volts for the embodiment wherein the second input 3110 is connected to electrical ground 3112). When the oscillating signal 3104 causes the switch 3116 to again become “open,” the amplitude of the harmonically rich signal 3114 again becomes substantially equal to the reference signal 3106. Thus, the amplitude of the harmonically rich signal 3114 is at either of two signal levels, i.e., reference signal 3106 or ground 3112, and has a frequency that is substantially equal to the frequency of the oscillating signal 3104 that causes the switch 3116 to open and close. In an alternate embodiment wherein the second input 3110 is connected to the second signal 3118, the harmonically rich signal 3114 varies between the reference signal 3106 and the second signal 3118. One skilled in the relevant art(s) will recognize that any one of a number of switch module designs will fulfill the scope and spirit of the present invention.
In an embodiment of the invention, the switch 3116 is a semiconductor device, such as a diode ring. In another embodiment, the switch is a transistor, such as, but not limited to, a field effect transistor (FET). In an embodiment wherein the FET is gallium arsenide (GaAs), the module can be designed as seen in
An alternate implementation of the design includes a “dwell capacitor” wherein one side of a capacitor is connected to the first input of the switch and the other side of the capacitor is connected to the second input of the switch. The purpose of the design is to increase the apparent aperture of the pulse without actually increasing its width. For additional detail on the design and use of a dwell capacitor, see co-pending application entitled “Method and System for Down-Converting Electromagnetic Signals Having Optimized Switch Structures,” Ser. No. 09/293,095, filed Apr. 16, 1999, and other applications as referenced above.
Other switch designs and implementations will be apparent to persons skilled in the relevant art(s).
The output 3122 of the switch module 3102, i.e., the harmonically rich signal 3114, can be routed to a filter 3504 in the AM mode.
3.3.8 The Summer (“I/Q” Mode).
As discussed above, the in-phase/quadrature-phase modulation (“I/Q”) mode embodiment of the invention uses a summer. See, as an example, summer 1832 in
3.3.8.1 Operational Description.
An “I” modulated signal 3404 and a “Q” modulated signal 3406 are combined and an “I/Q” modulated signal 3408 is generated. Generally, both “I” and “Q” modulated signals 3404 and 3406 are harmonically rich waveforms, which are referred to as the harmonically rich “I” signal 3404 and the harmonically rich “Q” signal 3406. Similarly, “I/Q” modulated signal 3408 is harmonically rich and is referred to as the harmonically rich “I/Q” signal. In one embodiment, these harmonically rich signals have substantially rectangular waveforms. As stated above, one skilled in the relevant art(s) will recognize the physical limitations to and mathematical obstacles against achieving exact or perfect waveforms and it is not the intent of the present invention that a perfect waveform be generated or needed.
In a typical embodiment, the harmonically rich “I” signal 3404 and the harmonically rich “Q” signal 3406 are phase modulated, as is the harmonically rich “I/Q” signal 3408. A person skilled in the relevant art(s) will recognize that other modulation techniques, such as amplitude modulating the “I/Q” signal, may also be used in the “I/Q” mode without deviating from the scope and spirit of the invention.
As stated before, a continuous and periodic waveform, such as harmonically rich “I/Q” signal 3408, has sinusoidal components (harmonics) at frequencies that are integer multiples of the fundamental frequency of the underlying waveform (the Fourier component frequencies). Thus, harmonically rich “I/Q” signal 3408 is composed of sinusoidal signals at frequencies that are integer multiples of the fundamental frequency of itself. These sinusoidal signals are also modulated substantially the same as the continuous and periodic waveform from which they are derived. That is, in this embodiment, the sinusoidal signals are phase modulated, and include the information from both the “I” modulated signal and the “Q” modulated signal.
3.3.8.2 Structural Description.
The design and use of a summer 3402 is well known to those skilled in the relevant art(s). A summer 3402 may be designed and fabricated from discrete components, or it may be purchased “off the shelf.” A summer 3402 accepts a harmonically rich “I” signal 3404 and a harmonically rich “Q” signal 3406, and combines them to create a harmonically rich “I/Q” signal 3408. In a preferred embodiment of the invention, the harmonically rich “I” signal 3404 and the harmonically rich “Q” signal 3406 are both phase modulated. When the harmonically rich “I” signal 3404 and the harmonically rich “Q” signal 3406 are both phase modulated, the harmonically rich “I/Q” signal 3408 is also phase modulated.
As stated before, a continuous and periodic waveform, such as the harmonically rich “I/Q” signal 3408, has sinusoidal components (harmonics) at frequencies that are integer multiples of the fundamental frequency of the underlying waveform (the Fourier component frequencies). Thus, the harmonically rich “I/Q” signal 3408 is composed of “I/Q” sinusoidal signals at frequencies that are integer multiples of the fundamental frequency of itself. These “I/Q” sinusoidal signals are also phase modulated substantially the same as the continuous and periodic waveform from which they are derived (i.e., the harmonically rich “I/Q” signal 3408).
The output of the summer 3402 is then routed to a filter 3504.
3.3.9 The Filter (FM, PM, AM, and “I/Q” Modes).
As discussed above, all modulation mode embodiments of the invention use a filter. See, as an example, filter 1218 in
3.3.9.1 Operational Description.
A modulated signal with a harmonically rich waveform 3502 is accepted. It is referred to as the harmonically rich signal 3502. As stated above, a continuous and periodic waveform, such as the harmonically rich signal 3502, is comprised of sinusoidal components (harmonics) at frequencies that are integer multiples of the fundamental frequency of the underlying waveform from which they are derived. These are called the Fourier component frequencies. In one embodiment of the invention, the undesired harmonic frequencies are removed, and the desired frequency 3506 is output. In an alternate embodiment, a plurality of harmonic frequencies are output.
The harmonic components of the harmonically rich signal 3502 are modulated in the same manner as the harmonically rich signal 3502 itself. That is, if the harmonically rich signal 3502 is frequency modulated, all of the harmonic components of that signal are also frequency modulated. The same is true for phase modulation, amplitude modulation, and “I/Q” modulation.
3.3.9.2 Structural Description.
The design and use of a filter 3504 is well known to those skilled in the relevant art(s). A filter 3504 may be designed and fabricated from discrete components or it may be purchased “off the shelf.” The filter 3504 accepts the harmonically rich signal 3502 from the switch module 2802 or 3102 in the FM, PM, and AM modes, and from the summer 3402 in the “I/Q” mode. The harmonically rich signal 3502 is a continuous and periodic waveform. As such, it is comprised of sinusoidal components (harmonics) that are at frequencies that are integer multiples of the fundamental frequency of the underlying harmonically rich signal 3502. The filter 3504 removes those sinusoidal signals having undesired frequencies. The signal 3506 that remains is at the desired frequency, and is called the desired output signal 3506.
To achieve this result, according to an embodiment of the invention, a filter 3504 is required to filter out the unwanted harmonics of the harmonically rich signal 3502.
The term “Q” is used to represent the ratio of the center frequency of the desired output signal 3506 to the half power band width. Looking at
For crisp broadcast frequencies, it is desired that Q be as high as possible and practical, based on the given application and environment. The purpose of the filter 3504 is to filter out the unwanted harmonics of the harmonically rich signal. The circuits are tuned to eliminate all other harmonics except for the desired frequency 3506 (e.g., the 900 MHz harmonic 3602). Turning now to
The modulated signal at the desired frequency 3506 may then be routed to the transmission module 3804.
3.3.10 The Transmission Module (FM, PM, AM, and “IV” Modes).
As discussed above, the modulation mode embodiments of the invention preferably use a transmission module. See, as an example, transmission module 1222 in
3.3.10.1 Operational Description.
A modulated signal at the desired frequency 3802 is accepted and is transmitted over the desired medium, such as, but not limited to, over-the-air broadcast or point-to-point cable.
3.3.10.2 Structural Description.
The transmission module 3804 receives the signal at the desired EM frequency 3802. If it is intended to be broadcast over the air, the signal may be routed through an optional antenna interface and then to the antenna for broadcast. If it is intended for the signal to be transmitted over a cable from one point to another, the signal may be routed to an optional line driver and out through the cable. One skilled in the relevant art(s) will recognize that other transmission media may be used.
3.3.11 Other Implementations.
The implementations described above are provided for purposes of illustration. These implementations are not intended to limit the invention. Other implementation embodiments are possible and covered by the invention, such as but not limited to software, software/hardware, and firmware implementations of the systems and components of the invention. Alternate implementations and embodiments, differing slightly or substantially from those described herein, will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such alternate implementations fall within the scope and spirit of the present invention.
4. HARMONIC ENHANCEMENT 4.1 High Level DescriptionThis section (including its subsections) provides a high-level description of harmonic enhancement according to the present invention. In particular, pulse shaping is described at a high-level. Also, a structural implementation for achieving this process is described at a high-level. This structural implementation is described herein for illustrative purposes, and is not limiting. In particular, the process described in this section can be achieved using any number of structural implementations, one of which is described in this section. The details of such structural implementations will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein.
It is noted that some embodiments of the invention include harmonic enhancement, whereas other embodiments do not.
4.1.1 Operational Description.
To better understand the generation and extraction of harmonics, and the purpose behind shaping the waveforms to enhance the harmonics, the following discussion of Fourier analysis as it applies to the present invention is offered.
A discovery made by Baron Jean B. J. Fourier (1768-1830) showed that continuous and periodic waveforms are comprised of a plurality of sinusoidal components, called harmonics. More importantly, the frequency of these components are integer multiples of the frequency of the original waveform (called the fundamental frequency). The amplitude of each of these component waveforms depends on the shape of the original waveform. The derivations and proofs of Baron Fourier's analysis are well known to those skilled in the relevant art(s).
The most basic waveform which is continuous and periodic is a sine wave. It has but one harmonic, which is at the fundamental frequency. This is also called the first harmonic. Since it only has one component, the amplitude of the harmonic component is equal to the amplitude of the original waveform, i.e., the sine wave itself. The sine wave is not considered to be “harmonically rich.”
An impulse train is the other extreme case of a periodic waveform. Mathematically, it is considered to have zero width. The mathematical analysis in this case shows that there are harmonics at all multiples of the frequency of the impulse. That is, if the impulse has a frequency of Fi, then the harmonics are sinusoidal waves at 1·Fi, 2·Fi, 3·Fi, 4·Fi, etc. As the analysis also shows in this particular case, the amplitude of all of the harmonics are equal. This is indeed, a “harmonically rich” waveform, but is realistically impractical with current technology.
A more typical waveform is a rectangular wave, which is a series of pulses. Each pulse will have a width (called a pulse width, or “τ”), and the series of pulses in the waveform will have a period (“T” which is the inverse of the frequency, i.e., T=1/Fr, where “Fr” is the fundamental frequency of the rectangular wave). One form of rectangular wave is the square wave, where the signal is at a first state (e.g., high) for the same amount of time that it is at the second state (e.g., low). That is, the ratio of the pulse width to period (τ/T) is 0.5. Other forms of rectangular waves, other than square waves, are typically referred to simply as “pulses,” and have τ/T<0.5 (i.e., the signal will be “high” for a shorter time than it is “low”). The mathematical analysis shows that there are harmonics at all of the multiples of the fundamental frequency of the signal. Thus, if the frequency of the rectangular waveform is Fr, then the frequency of the first harmonic is 1·Fr, the frequency of the second harmonic is 2·Fr, the frequency of the third harmonic is 3·Fr, and so on. There are some harmonics for which the amplitude is zero. In the case of a square wave, for example, the “null points” are the even harmonics. For other values of τ/T, the “null points” can be determined from the mathematical equations. The general equation for the amplitude of the harmonics in a rectangular wave having an amplitude of Apulse is as follows:
Amplitude(nth harmonic)=An={[Apulse][(2/π)/n] sin [n·π·(τ/T)]} Eq. 1
Table 6000 of
From the foregoing, it can be seen how pulse width is an important factor in assuring that the harmonic waveform at the desired output frequency has sufficient amplitude to be useful without requiring elaborate filtering or unnecessary amplification.
Another factor in assuring that the desired harmonic has sufficient amplitude is how the switch 2816 and 3116 (
It is an objective of this invention in the transmitter embodiment that the intelligence in the information signal is to be transmitted. That is, the information is modulated onto the transmitted signal. In the FM and PM modes, to achieve this objective, the information signal is used to modulate the oscillating signal 2804. The oscillating signal 2804 then causes the switch 2816 to close and open. The information that is modulated onto the oscillating signal 2804 must be faithfully reproduced onto the signal that is output from the switch circuit (i.e., the harmonically rich signal 2814). For this to occur efficiently, in embodiments of the invention, the switch 2816 preferably closes and opens crisply so that the harmonically rich signal 2814 changes rapidly from the bias/reference signal 2806 (or 3106) to ground 2812 (or the second signal level 2818 in the alternate embodiment). This rapid rise and fall time is desired so that the harmonically rich signal 2814 will be “harmonically rich.” (In the case of AM, the oscillating signal 3104 is not modulated, but the requirement for “crispness” still applies.)
For the switch 2816 to close and open crisply, the oscillating signal 2804 must also be crisp. If the oscillating signal 2804 is sinusoidal, the switch 2816 will open and close when the threshold voltages are reached, but the pulse width of the harmonically rich signal 2814 may not be as small as is needed to ensure the amplitude of the desired harmonic of the harmonically rich signal 2814 is sufficiently high to allow transmission without elaborate filtering or unnecessary amplification. Also, in the embodiment wherein the switch 2816 is a GaAsFET 2901, if the oscillating signal 2804 that is connected to the gate 2902 of the GaAsFET 2901 (i.e., the signal that causes the switch 2816 to close and open) is a sinusoidal wave, the GaAsFET 2901 will not crisply close and open, but will act more like an amplifier than a switch. (That is, it will conduct during the time that the oscillating signal is rising and falling below the threshold voltages, but will not be a “short.”) In order to make use of the benefits of a GaAsFET's capability to close and open at high frequencies, the oscillating signal 2804 connected to the gate 2902 preferably has a rapid rise and fall time. That is, it is preferably a rectangular waveform, and preferably has a pulse width to period ratio the same as the pulse width to period ratio of the harmonically rich signal 2814.
As stated above, if a signal with a continuous and periodic waveform is modulated, that modulation occurs on every harmonic of the original waveform. Thus, in the FM and PM modes, when the information is modulated onto the oscillating signal 2804 and the oscillating signal 2804 is used to cause the switch 2816 to close and open, the resulting harmonically rich signal 2814 that is output from the switch module 2802 will also be modulated. If the oscillating signal 2804 is crisp, the switch 2816 will close and open crisply, the harmonically rich signal 2814 will be harmonically rich, and each of the harmonics of the harmonically rich signal 2814 will have the information modulated on it.
Because it is desired that the oscillating signal 2804 be crisp, harmonic enhancement may be needed in some embodiments. Harmonic enhancement may also be called “pulse shaping” since the purpose is to shape the oscillating signal 2804 into a string of pulses of a desired pulse width. If the oscillating signal is sinusoidal, harmonic enhancement will shape the sinusoidal signal into a rectangular (or substantially rectangular) waveform with the desired pulse width to period ratio. If the oscillating signal 2804 is already a square wave or a pulse, harmonic enhancement will shape it to achieve the desired ratio of pulse width to period. This will ensure an efficient transfer of the modulated information through the switch.
Three exemplary embodiments of harmonic enhancement are described below for illustrative purposes. However, the invention is not limited to these embodiments. Other embodiments will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein.
4.1.2 Structural Description.
The shape of the oscillating signal 2804 causes the switch 2816 to close and open. The shape of the oscillating signal 2804 and the selection of the switch 2816 will determine how quickly the switch 2816 closes and opens, and how long it stays closed compared to how long it stays open. This then will determine the “crispness” of the harmonically rich signal 2814. (That is, whether the harmonically rich signal 2814 is substantially rectangular, trapezoidal, triangular, etc.) As shown above, in order to ensure that the desired harmonic has the desired amplitude, the shape of the oscillating signal 2804 should be substantially optimized.
The harmonic enhancement module (HEM) 4602 (
In the embodiment described above in sections 3.3.6-3.3.6.2 (and 3.3.7-3.3.7.2), when the switch 2816 (or 3116) is open, the harmonically rich signal 2814 (or 3114) will have an amplitude substantially equal to the bias signal 2806 (or reference signal 3106). When the switch 2816 (or 3116) is closed, the harmonically rich signal 2814 (or 3114) will have an amplitude substantially equal to the potential of signal 2812 or 2818 (or 3112 or 3118) of the second input 2810 (or 3110) of the switch module 2802 (or 3102). Thus, for the case where the oscillating signal 2804 (or 3104) driving the switch module 2802 (or 3102) is substantially rectangular, the harmonically rich signal 2814 (or 3114) will have substantially the same frequency and pulse width as the shaped oscillating signal 2804 (or 3104) that drives the switch module 2802 (or 3102). This is true for those cases wherein the oscillating signal 2804 (or 3104) is a rectangular wave. One skilled in the relevant art(s) will understand that the term “rectangular wave” can refer to all waveforms that are substantially rectangular, including square waves and pulses.
The purpose of shaping the signal is to control the amount of time that the switch 2816 (or 3116) is closed. As stated above, the harmonically rich signal 2814 (or 3114) has a substantially rectangular waveform. Controlling the ratio of the pulse width of the harmonically rich signal 2814 (or 3114) to its period will result in the shape of the harmonically rich signal 2814 (or 3114) being substantially optimized so that the relative amplitudes of the harmonics are such that the desired harmonic can be extracted without unnecessary and elaborate amplification and filtering.
4.2 Exemplary EmbodimentsVarious embodiments related to the method(s) and structure(s) described above are presented in this section (and its subsections). These embodiments are described herein for purposes of illustration, and not limitation. The invention is not limited to these embodiments. Alternate embodiments (including equivalents, extensions, variations, deviations, etc., of the embodiments described herein) will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. The invention is intended and adapted to include such alternate embodiments.
4.2.1 First Embodiment When a Square Wave Feeds the Harmonic Enhancement Module to Create One Pulse per Cycle4.2.1.1 Operational Description.
According to this embodiment, a continuous periodic waveform 4604 is received and a string of pulses 4606 is output. The continuous periodic waveform 4604 may be a square wave or any other continuous periodic waveform that varies from a value recognized as a “digital low” to a value recognized as a “digital high.” One pulse is generated per cycle of the continuous and periodic waveform 4604. The description given herein will be for the continuous periodic waveform 4604 that is a square wave, but one skilled in the relevant art(s) will appreciate that other waveforms may also be “shaped” into waveform 4606 by this embodiment.
4.2.1.2 Structural Description.
In this first embodiment of a harmonic enhancement module 4602, herein after referred to as a pulse shaping circuit 4602, a continuous periodic waveform 4604 that is a square wave is received by the pulse shaping circuit 4602. The pulse shaping circuit 4602 is preferably comprised of digital logic devices that result in a string of pulses 4606 being output that has one pulse for every pulse in the continuous periodic waveform 4604, and preferably has a τ/T ratio less than 0.5.
4.2.2 Second Embodiment When a Square Wave Feeds the Harmonic Enhancement Module to Create Two Pulses per Cycle4.2.2.1 Operational Description.
In this embodiment, a continuous periodic waveform 4604 is received and a string of pulses 4606 is output. In this embodiment, there are two pulses output for every period of the continuous periodic waveform 4604. The continuous periodic waveform 4604 may be a square wave or any other continuous periodic waveform that varies from a value recognized as a “digital low” to a value recognized as a “digital high.” The description given herein will be for a continuous periodic waveform 4604 that is a square wave, but one skilled in the relevant art(s) will appreciate that other waveforms may also be “shaped” into waveform 4606 by this embodiment.
4.2.2.2 Structural Description.
In this second embodiment of a pulse shaping circuit 4602, a continuous periodic waveform 4604 that is a square wave is received by the pulse shaping circuit 4602. The pulse shaping circuit 4602 is preferably comprised of digital logic devices that result in a string of pulses 4606 being output that has two pulses for every pulse in the continuous periodic waveform 4604, and preferably has a VT ratio less than 0.5.
4.2.3 Third Embodiment When Any Waveform Feeds the Module4.2.3.1 Operational Description.
In this embodiment, a continuous periodic waveform 4604 of any shape is received and a string of pulses 4606 is output.
4.2.3.2 Structural Description.
In this third embodiment of a pulse shaping circuit 4602, a continuous periodic waveform 4604 of any shape is received by the pulse shaping circuit 4602. The pulse shaping circuit 4602 is preferably comprised of a series of stages, each stage shaping the waveform until it is substantially a string of pulses 4606 with preferably a τ/T ratio less than 0.5.
4.2.4 Other EmbodimentsThe embodiments described above are provided for purposes of illustration. These embodiments are not intended to limit the invention. Alternate embodiments, differing slightly or substantially from those described herein, will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such alternate embodiments fall within the scope and spirit of the present invention.
4.3 Implementation ExamplesExemplary operational and/or structural implementations related to the method(s), structure(s), and/or embodiments described above are presented in this section (and its subsections). These components and methods are presented herein for purposes of illustration, and not limitation. The invention is not limited to the particular examples of components and methods described herein. Alternatives (including equivalents, extensions, variations, deviations, etc., of those described herein) will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such alternatives fall within the scope and spirit of the present invention.
4.3.1 First Digital Logic Circuit.
An exemplary implementation of the first embodiment described in sections 4.2.1-4.2.1.2 is illustrated in
4.3.2 Second Digital Logic Circuit.
An exemplary implementation of the second embodiment described in sections 4.2.2-4.2.2.2 is illustrated in
4.3.3 Analog Circuit.
An exemplary implementation of the third embodiment described in sections 4.2.3-4.2.3.2 is illustrated in
An exemplary circuit for circuit elements 4104 is shown in
4.3.4 Other Implementations.
The implementations described above are provided for purposes of illustration. These implementations are not intended to limit the invention. Alternate implementations, differing slightly or substantially from those described herein, will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such alternate implementations fall within the scope and spirit of the present invention.
5. AMPLIFIER MODULE 5.1 High Level DescriptionThis section (including its subsections) provides a high-level description of the amplifier module according to the present invention. In particular, amplification is described at a high-level. Also, a structural implementation for achieving signal amplification is described at a high-level. This structural implementation is described herein for illustrative purposes, and is not limiting. In particular, the process described in this section can be achieved using any number of structural implementations, one of which is described in this section. The details of such structural implementations will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein.
5.1.1 Operational Description.
Even though the present invention is intended to be used without requiring amplification, there may be circumstance when, in the embodiment of the present invention wherein it is being used as a transmitter, it may prove desirable to amplify the modulated signal before it is transmitted. In another embodiment of the invention wherein it is being used as a stable signal source for a frequency or phase comparator, it may also be desirable to amplify the resultant signal at the desired frequency.
The requirement may come about for a number of reasons. A first may be that the bias/reference signal is too low to support the desired use. A second may be because the desired output frequency is very high relative to the frequency of the oscillating signal that controls the switch. A third reason may be that the shape of the harmonically rich signal is such that the amplitude of the desired harmonic is low.
In the first case, recall that the amplitude of the bias/reference signal determines the amplitude of the harmonically rich signal which is present at the output of the switch circuit. (See sections 3.3.6-3.3.6.2 and 3.3.7-3.3.7.2.) Further recall that the amplitude of the harmonically rich signal directly impacts the amplitude of each of the harmonics. (See the equation in section 4.1, above.)
In the second instance, if the frequency of the oscillating signal is relatively low compared to the desired output frequency of the up-converter, a high harmonic will be needed. As an example, if the oscillating signal is 60 MHz, and the desired output frequency is at 900 MHz, the 15th harmonic will be needed. In the case where τ/T is 0.1, it can be seen from Table 6000 of
The third circumstance wherein the amplitude of the output may need to be amplified is when the shape of the harmonically rich signal in not “crisp” enough to provide harmonics with enough amplitude for the desired purpose. If, for example, the harmonically rich signal is substantially triangular, and given the example above where the oscillating signal is 60 MHz and the desired output signal is 900 MHz, the 15th harmonic of the triangular wave is 0.00180. This is significantly lower than the amplitude of the 15th harmonic of the “0.1” rectangular wave (shown above to be 0.0424) and can be mathematically shown to be 0.4% of the amplitude of the 1st harmonic of the triangular wave (which is 0.405). Thus, in this example, the 1st harmonic of the triangular wave has an amplitude that is larger than the amplitude of the 1st harmonic of the “0.1” rectangular wave, but at the 15th harmonic, the triangular wave is significantly lower than the “0.1” rectangular wave.
Another reason that the desired harmonic may need to be amplified is that circuit elements such as the filter may cause attenuation in the output signal for which a designer may wish to compensate.
The desired output signal can be amplified in a number of ways. One is to amplify the bias/reference signal to ensure that the amplitude of the harmonically rich wave form is high. A second is to amplify the harmonically rich waveform itself. A third is to amplify the desired harmonic only. The examples given herein are for illustrative purposes only and are not meant to be limiting on the present invention. Other techniques to achieve amplification of the desired output signal would be apparent to those skilled in the relevant art(s).
5.1.2 Structural Description.
In one embodiment, a linear amplifier is used to amplify the bias/reference signal. In another embodiment, a linear amplifier is used to amplify the harmonically rich signal. And in yet another embodiment, a linear amplifier is used to amplify the desired output signal. Other embodiments, including the use of non-linear amplifiers, will be apparent to persons skilled in the relevant art(s).
5.2 Exemplary EmbodimentAn embodiment related to the method(s) and structure(s) described above is presented in this section (and its subsections). This embodiment is described herein for purposes of illustration, and not limitation. The invention is not limited to this embodiment. Alternate embodiments (including equivalents, extensions, variations, deviations, etc., of the embodiment described herein) will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. The invention is intended and adapted to include such alternate embodiments.
5.2.1 Linear AmplifierThe exemplary linear amplifier described herein will be directed towards an amplifier composed of solid state electronic devices to be inserted in the circuit at one or more points. Other amplifiers suitable for use with the invention will be apparent to persons skilled in the relevant art(s). As shown in
5.2.1.1 Operational Description.
The desired output signal can be amplified in a number of ways. Such amplification as described in the section may be in addition to the techniques described above to enhance the shape of the harmonically rich signal by pulse shaping of the oscillating signal that causes the switch to close and open.
5.2.1.2 Structural Description.
In one embodiment, a linear amplifier is placed between the bias/reference signal and the switch module. This will increase the amplitude of the bias/reference signal, and as a result, will raise the amplitude of the harmonically rich signal that is the output of the switch module. This will have the effect of not only raising the amplitude of the harmonically rich signal, it will also raise the amplitude of all of the harmonics. Some potential limitation of this embodiment are: the amplified bias/reference signal may exceed the voltage design limit for the switch in the switch circuit; the harmonically rich signal coming out of the switch circuit may have an amplitude that exceeds the voltage design limits of the filter; and/or unwanted distortion may occur from having to amplify a wide bandwidth signal.
A second embodiment employs a linear amplifier between the switch module and the filter. This will raise the amplitude of the harmonically rich signal. It will also raise the amplitude of all of the harmonics of that signal. In an alternate implementation of this embodiment, the amplifier is tuned so that it only amplifies the desired frequencies. Thus, it acts both as an amplifier and as a filter. A potential limitation of this embodiment is that when the harmonically rich signal is amplified to raise a particular harmonic to the desired level the amplitude of the whole waveform is amplified as well. For example, in the case where the amplitude of the pulse, Apulse, is equal to 1.0, to raise the 15th harmonic from 0.0424 volts to 0.5 volts, the amplitude of each pulse in the harmonically rich signal, Apulse, will increase from 1.0 to 11.8 volts. This may well exceed the voltage design limit of the filter.
A third embodiment of an amplifier module will place a linear amplifier between the filter and the transmission module. This will only raise the amplitude of the desired harmonic, rather than the entire harmonically rich signal.
Other embodiments, such as the use of non-linear amplifiers, will be apparent to one skilled in the relevant art(s), and will not be described herein.
5.2.2 Other EmbodimentsThe embodiments described above are provided for purposes of illustration. These embodiments are not intended to limit the invention. Alternate embodiments, differing slightly or substantially from those described herein, will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such alternate embodiments fall within the scope and spirit of the present invention.
5.3 Implementation ExamplesExemplary operational and/or structural implementations related to the method(s), structure(s), and/or embodiments described above are presented in this section (and its subsections). These components and methods are presented herein for purposes of illustration, and not limitation. The invention is not limited to the particular examples of components and methods described herein. Alternatives (including equivalents, extensions, variations, deviations, etc., of those described herein) will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such alternatives fall within the scope and spirit of the present invention.
5.3.1 Linear Amplifier.
Although described below as if it were placed after the filter, the amplifier may also be placed before the filter without deviating from the intent of the invention
5.3.1.1 Operational Description.
According to embodiments of the invention, a linear amplifier receives a first signal at a first amplitude, and outputs a second signal at a second amplitude, wherein the second signal is proportional to the first signal. It is a objective of an amplifier that the information embedded onto the first signal waveform will also be embedded onto the second signal. Typically, it is desired that there be as little distortion in the information as possible.
In a preferred embodiment, the second signal is higher in amplitude than the first signal, however, there may be implementations wherein it is desired that the second signal be lower than the first signal (i.e., the first signal will be attenuated).
5.3.1.2 Structural Description.
The design and use of a linear amplifier is well known to those skilled in the relevant art(s). A linear amplifier may be designed and fabricated from discrete components, or it may be purchased “off the shelf.”
Exemplary amplifiers are seen in
5.3.2 Other Implementations.
The implementations described above are provided for purposes of illustration. These implementations are not intended to limit the invention. Alternate implementations, differing slightly or substantially from those described herein, will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such alternate implementations fall within the scope and spirit of the present invention.
6. RECEIVER/TRANSMITTER SYSTEMThe present invention is for a method and system for up-conversion of electromagnetic signals. In one embodiment, the invention is a source of a stable high frequency reference signal. In a second embodiment, the invention is a transmitter.
This section describes a third embodiment. In the third embodiment, the transmitter of the present invention to be used in a receiver/transmitter communications system. This third embodiment may also be referred to as the communications system embodiment, and the combined receiver/transmitter circuit is referred to as a “transceiver.” There are several alternative enhancements to the communications systems embodiment.
The following sections describe systems and methods related to exemplary embodiments for a receiver/transmitter system. It should be understood that the invention is not limited to the particular embodiments described below. Equivalents, extensions, variations, deviations, etc., of the following will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such equivalents, extensions, variations, deviations, etc., are within the scope and spirit of the present invention.
6.1 High Level DescriptionThis section provides a high-level description of a receiver/transmitter system according to the present invention. The implementations are described herein for illustrative purposes, and are not limiting. In particular, any number of functional and structural implementations may be used, several of which are described in this section. The details of such functional and structural implementations will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein.
According to a first embodiment of the transmitter of the present invention is used with a traditional superheterodyne receiver. In this embodiment, the transmitter and the receiver can operate either in a full-duplex mode or in a half-duplex mode. In a full duplex mode, the transceiver can transmit and receive simultaneously. In the half-duplex mode, the transceiver can either transmit or receive, but cannot do both simultaneously. The full-duplex and the half-duplex modes will be discussed together for this embodiment.
A second embodiment of the transceiver is for the transmitter of the present invention to be used with a universal frequency down conversion circuit being used as a receiver. In this embodiment the transceiver is used in a half-duplex mode.
A third embodiment of the transceiver is for the transmitter of the present invention to be used with a universal frequency down conversion circuit, where the transceiver is used in a full-duplex mode.
These embodiments of the transceiver are described below.
6.2 Exemplary Embodiments and Implementation ExamplesVarious embodiments related to the method(s) and structure(s) described above and exemplary operational and/or structural implementations related to those embodiments are presented in this section (and its subsections). These embodiments, components, and methods are described herein for purposes of illustration, and not limitation. The invention is not limited to these embodiments or to the particular examples of components and methods described herein. Alternatives (including equivalents, extensions, variations, deviations, etc., of those described herein) will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such alternatives fall within the scope and spirit of the present invention, and the invention is intended and adapted to include such alternatives.
6.2.1 First Embodiment The Transmitter of the Present Invention Being Used in a Circuit with a Superheterodyne ReceiverA typical superheterodyne receiver is shown in
A local oscillator 4914 generates an oscillating signal 4916 which is combined with signal 4911 by mixer 4912. The output of mixer 4912 is a signal 4934 which is amplified by an amplifier 4918 and filtered by a filter 4920. The purpose of amplifier 4918 is to ensure that the strength of signal 4934 is sufficient for further processing, and the purpose of filter 4920 is to remove the undesired frequencies.
A second local oscillator 4924 generates a second oscillating signal 4926 which is combined with the amplified/filtered signal 4934 by a mixer 4922. The output of mixer 4922 is signal 4936. Again, an amplifier 4928 and a filter 4930 ensure that the signal 4936 is at the desired amplitude and frequency. The resulting signal is then routed to decoder 4932 where the intelligence is extracted to obtain baseband signal 4938.
Signal 4934 is referred to as the first intermediate frequency (IF) signal, and signal 4936 is referred to as the second IF signal. Thus, the combination of local oscillator 4914 and mixer 4912 can be referred to as the first IF stage, and the combination of local oscillator 4924 and mixer 4922 can be referred to as the second IF stage.
Exemplary frequencies for the circuit of
Other superheterodyne receiver configurations are well known and these can be used in the transceiver embodiments of the invention. Also, the exemplary frequencies mentioned above are provide for illustrative purposes only, and are not limiting.
In the FM and PM modes, an information signal 5004 modulates an intermediate signal to produce the oscillating signal 5002. Oscillating signal 5002 is shaped by signal shaper 5010 to produce a string of pulses 5008 (see the discussion above regarding the benefits of harmonic enhancement). The string of pulses 5008 drives the switch module 5012. In the FM/PM modes, a bias/reference signal 5006 is also received by switch module 5012. The output of switch module 5012 is a harmonically rich signal 5022. Harmonically rich signal 5022 is comprised of a plurality of sinusoidal components, and is routed to a “high Q” filter that will remove all but the desired output frequency(ies). The desired output frequency 5024 is amplified by an amplifier 5016 and routed to a transmission module 5018 which outputs a transmission signal 5026 which is routed to a duplexer 5020. The purpose of duplexer 5020 is to permit a single antenna to be used simultaneously for both receiving and transmitting signals. The combination of received signal 4902 and transmission signal 5026 is a duplexed signal 5028.
In the AM mode, the same circuit of
This description is for the full-duplex mode of the transceiver wherein the transmitting portion of the communications system is a separate circuit than the receiver portion. A possible embodiment of a half-duplex mode is described below.
Alternate embodiments of the transceiver are possible. For example,
As described in the example above, a typical second IF frequency is 11 MHz. The selection of this IF frequency is less flexible than is the selection of the first IF frequency, since the second IF frequency is routed to a decoder where the signal is demodulated and decoded. Typically, demodulators and decoders are designed to receive signals at a predetermined, fixed frequency, e.g., 11 MHz. If this is the case, the combination of the first IF signal 5108 and the second oscillating signal 5112 must generate a second IF signal with a second IF frequency of 11 MHz. Recall that the received signal 4902 was 900 MHz in the example above. To achieve the second IF signal frequency of 11 MHz, the frequencies of the oscillating signals 4916 and 4926 were set at 830 MHz and 59 MHz. Before setting the frequencies of the oscillating signals 5106 and 5112, the desired frequency of the transmitted signal must be determined. If it, too, is 900 MHz, then the frequency of the oscillating signal that causes the switch in the present invention to open and close must be a “sub-harmonic” of 900 MHz. That is, it must be the quotient of 900 MHz divided by an integer. (In other words, 900 MHz must be a harmonic of the oscillating signal that drives the switch.) The table below is a list of some of the sub-harmonics of 900 MHz:
Recall that the frequency of the second oscillating signal 4926 in
The frequency of the first oscillating signal 5106 can be determined from the values of the first IF frequency and the frequency of the received signal 4902. In this example, the frequency of the received signal is 900 MHz and the frequency of the first IF signal is 71 MHz. Therefore, the frequency of the first oscillating signal 5106 must be 829 MHz, as indicated below:
Thus the frequencies of the oscillating signals 5106 and 5112 are 829 MHz and 60 MHz, respectively.
In
In
The scope of the invention includes an FM embodiment wherein the oscillator 5110 of the receiver circuit is used as a source for an oscillating signal for the transmitter circuit. In the embodiments discussed above, the FM embodiment requires a voltage controlled oscillator (VCO) rather than a simple local oscillator. There are circuit designs that would be apparent to those skilled in the relevant art(s) based on the discussion contained herein, wherein a VCO is used in place of a local oscillator in the receiver circuit.
In
Those skilled in the relevant art(s) will understand that there are numerous combinations of oscillator frequencies, stages, and circuits that will meet the scope and intent of this invention. Thus, the description included herein is for illustrative purposes only and not meant to be limiting.
6.2.2 Second Embodiment The Transmitter of the Present Invention Being Used with a Universal Frequency Down-Converter in a Half-Duplex ModeAn exemplary receiver using universal frequency down conversion techniques is shown in
PM embodiments, an information signal 5302 modulates an oscillating signal 5306 which is routed to a pulse shaping circuit 5310 which outputs a string of pulses 5311. The string of pulses 5311 controls the opening and closing of the switch 5312. One terminal of switch 5312 is connected to ground 5314, and the second terminal of switch 5312 is connected through a resistor 5330 to a bias/reference signal 5308. In the FM and PM modes, bias/reference signal 5308 is preferably a non-varying signal, often referred to simply as the bias signal. In the AM mode, the oscillating signal 5306 is not modulated, and the bias/reference signal is a function of the information signal 5304. In one embodiment, information signal 5304 is combined with a bias voltage to generate the reference signal 5308. In an alternate embodiment, the information signal 5304 is used without being combined with a bias voltage. Typically, in the AM mode, this bias/reference signal is referred to as the reference signal to distinguish it from the bias signal used in the FM and PM modes. The output of switch 5312 is a harmonically rich signal 5316 which is routed to a “high Q” filter which removes the unwanted frequencies that exist as harmonic components of harmonically rich signal 5316. Desired frequency 5320 is amplified by amplifier module 5322 and routed to transmission module 5324 which outputs a transmission signal 5326. Transmission signal is output by antenna 5328 in this embodiment.
For the FM and PM modulation modes,
Oscillating signal 5436 is shaped by pulse shaper 5438 to produce a string of pulses 5440. The string of pulses 5440 cause the switch 5420 to open and close. As a result of the switch opening and closing, a down converted signal 5409 is generated. The down converted signal 5409 is amplified and filtered to create a filtered signal 5413. In an embodiment, filtered signal 5413 is at baseband and, as a result of the down conversion, is demodulated. Thus, a decoder 5414 may not be required except to convert digital to analog or to decrypt the filtered signal 5413. In an alternate embodiment, the filtered signal 5413 is at an “offset” frequency, so that the decoder 5414 is needed to demodulate the filtered signal and create a demodulated baseband signal.
When the transceiver is performing the transmit function, the R/T switches 5406, 5408, and 5446/5452 (FM or PM) are in the (T) position. In the FM modulation mode, an information signal 5450 is connected by switch 5446 to VCO 5444 to create a frequency modulated oscillating signal 5436. In the PM modulation mode switch 5452 connects information signal 5450 to the phase modulator 5456 to create a phase modulated oscillating signal 5436. Oscillation signal 5436 is routed through pulse shaper 5438 to create a string of pulses 5440 which in turn cause switch 5420 to open and close. One terminal of switch 5420 is connected to ground 5442 and the other is connected through switch R/T 5408 and resistor 5423 to a bias signal 5422. The result is a harmonically rich signal 5424 which is routed to a “high Q” filter 5426 which removes the unwanted frequencies that exist as harmonic components of harmonically rich signal 5424. Desired frequency 5428 is amplified by amplifier module 5430 and routed to transmission module 5432 which outputs a transmission signal 5434. Again, because the transceiver is performing the transmit function, R/T switch 5406 connects the transmission signal to the antenna 5402.
In the AM modulation mode, the transceiver operates in the half duplex mode as shown in
The full-duplex mode differs from the half-duplex mode in that the transceiver can transmit and receive simultaneously. Referring to
The receiver function performs as follows. The antenna 5602 receives an EM signal 5606 and routes it through a capacitor 5607 to one terminal of a switch 5626. The other terminal of switch 5626 is connected to ground 5628, and the switch is driven as a result of a string of pulses 5624 created by local oscillator 5620 and pulse shaper 5622. The opening and closing of switch 5626 generates a down converted signal 5614. Down converted signal 5614 is routed through a amplifier 5608 and a filter 5610 to generate filtered signal 5616. Filtered signal 5616 may be at baseband and be demodulated or it may be at an “offset” frequency. If filtered signal 5616 is at an offset frequency, decoder 5612 will demodulate it to create the demodulated baseband signal 5618. In a preferred embodiment, however, the filtered signal 5616 will be a demodulated baseband signal, and decoder 5612 may not be required except to convert digital to analog or to decrypt filtered signal 5616. This receiver portion of the transceiver can operate independently from the transmitter portion of the transceiver.
The transmitter function is performed as follows. In the FM and PM modulation modes, an information signal 5648 modulates an oscillating signal 5630. In the AM modulation mode, the oscillating signal 5630 is not modulated. The oscillating signal is shaped by pulse shaper 5632 and a string of pulses 5634 is created. This string of pulses 5634 causes a switch 5636 to open and close. One terminal of switch 5636 is connected to ground 5638, and the other terminal is connected through a resistor 5647 to a bias/reference signal 5646. In the FM and PM modulation modes, bias/reference signal 5646 is referred to as a bias signal 5646, and it is substantially non-varying. In the AM modulation mode, an information signal 5650 may be combined with the bias signal to create what is referred to as the reference signal 5646. The reference signal 5646 is a function of the information signal 5650. It is well known to those skilled in the relevant art(s) that the information signal 5650 may be used as the bias/reference signal 5646 directly without being summed with a bias signal. A harmonically rich signal 5652 is generated and is filtered by a “high Q” filter 5640, thereby producing a desired signal 5654. The desired signal 5654 is amplified by amplifier 5642 and routed to transmission module 5644. The output of transmission module 5644 is transmission signal 5656. Transmission signal 5656 is routed to duplexer 5604 and then transmitted by antenna 5602. This transmitter portion of the transceiver can operate independently from the receiver portion of the transceiver.
Thus, as described above, the transceiver embodiment the present invention as shown in
Other embodiments and implementations of the receiver/transmitter of the present invention would be apparent to one skilled in the relevant art(s) based on the discussion herein.
The embodiments and implementations described above are provided for purposes of illustration. These embodiments and implementations are not intended to limit the invention. Alternatives, differing slightly or substantially from those described herein, will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such alternate embodiments and implementations fall within the scope and spirit of the present invention.
6.3 Summary Description of Down-Conversion Using a Universal Frequency Translation ModuleThe following discussion describes down-converting using a Universal Frequency Translation Module. The down-conversion of an EM signal by aliasing the EM signal at an aliasing rate is fully described in co-pending U.S. patent application entitled “Method and System for Down-Converting Electromagnetic Signals,” Ser. No. 09/176,022, filed Oct. 21, 1998, the full disclosure of which is incorporated herein by reference. A relevant portion of the above mentioned patent application is summarized below to describe down-converting an input signal to produce a down-converted signal that exists at a lower frequency or a baseband signal.
In one implementation, aliasing module 6400 down-converts the input signal 6404 to an intermediate frequency (IF) signal. In another implementation, the aliasing module 6400 down-converts the input signal 6404 to a demodulated baseband signal. In yet another implementation, the input signal 6404 is a frequency modulated (FM) signal, and the aliasing module 6400 down-converts it to a non-FM signal, such as a phase modulated (PM) signal or an amplitude modulated (AM) signal. Each of the above implementations is described below.
In an embodiment, the control signal 6406 includes a train of pulses that repeat at an aliasing rate that is equal to, or less than, twice the frequency of the input signal 6404 In this embodiment, the control signal 6406 is referred to herein as an aliasing signal because it is below the Nyquist rate for the frequency of the input signal 6404. Preferably, the frequency of control signal 6406 is much less than the input signal 6404.
The train of pulses 6418 as shown in
Exemplary waveforms are shown in
As noted above, the train of pulses 6420 (i.e., control signal 6406) control the switch 6408 to alias the analog AM carrier signal 6416 (i.e., input signal 6404) at the aliasing rate of the aliasing signal 6418. Specifically, in this embodiment, the switch 6408 closes on a first edge of each pulse and opens on a second edge of each pulse. When the switch 6408 is closed, input signal 6404 is coupled to the capacitor 6410, and charge is transferred from the input signal 6404 to the capacitor 6410. The charge transferred during a pulse is referred to herein as an under-sample. Exemplary under-samples 6422 form down-converted signal portion 6424 (
The waveforms shown in
The aliasing rate of control signal 6406 determines whether the input signal 6404 is down-converted to an IF signal, down-converted to a demodulated baseband signal, or down-converted from an FM signal to a PM or an AM signal. Generally, relationships between the input signal 6404, the aliasing rate of the control signal 6406, and the down-converted output signal 6412 are illustrated below:
(Freq. of input signal 6404)=n·(Freq. of control signal 6406)±(Freq. of down-converted output signal 6412)
For the examples contained herein, only the “+” condition will be discussed. The value of n represents a harmonic or sub-harmonic of input signal 6404 (e.g., n=0.5, 1, 2, 3, . . . ).
When the aliasing rate of control signal 6406 is off-set from the frequency of input signal 6404, or off-set from a harmonic or sub-harmonic thereof, input signal 6404 is down-converted to an IF signal. This is because the under-sampling pulses occur at different phases of subsequent cycles of input signal 6404. As a result, the under-samples form a lower frequency oscillating pattern. If the input signal 6404 includes lower frequency changes, such as amplitude, frequency, phase, etc., or any combination thereof, the charge stored during associated under-samples reflects the lower frequency changes, resulting in similar changes on the down-converted IF signal. For example, to down-convert a 901 MHz input signal to a 1 MHz IF signal, the frequency of the control signal 6406 would be calculated as follows:
(Freqinput−FreqIF)/n=Freqcontrol
(901 MHz−1 MHz)/n=900/n
For n=0.5, 1, 2, 3, 4, etc., the frequency of the control signal 6406 would be substantially equal to 1.8 GHz, 900 MHz, 450 MHz, 300 MHz, 225 MHz, etc.
Exemplary time domain and frequency domain drawings, illustrating down-conversion of analog and digital AM, PM and FM signals to IF signal, and exemplary methods and systems thereof, are disclosed in co-pending U.S. patent application entitled “Method and System for Down-Converting Electromagnetic Signals,” Ser. No. 09/176,022, filed Oct. 21, 1998.
Alternatively, when the aliasing rate of the control signal 6406 is substantially equal to the frequency of the input signal 6404, or substantially equal to a harmonic or sub-harmonic thereof, input signal 6404 is directly down-converted to a demodulated baseband signal. This is because, without modulation, the under-sampling pulses occur at the same point of subsequent cycles of the input signal 6404. As a result, the under-samples form a constant output baseband signal. If the input signal 6404 includes lower frequency changes, such as amplitude, frequency, phase, etc., or any combination thereof, the charge stored during associated under-samples reflects the lower frequency changes, resulting in similar changes on the demodulated baseband signal. For example, to directly down-convert a 900 MHz input signal to a demodulated baseband signal (i.e., zero IF), the frequency of the control signal 6406 would be calculated as follows:
(Freqinput−FreqIF)/n=Freqcontrol
(900 MHz−0 MHz)/n=900 MHz/n
For n=0.5, 1, 2, 3, 4, etc., the frequency of the control signal 6406 should be substantially equal to 1.8 GHz, 900 MHz, 450 MHz, 300 MHz, 225 MHz, etc.
Exemplary time domain and frequency domain drawings, illustrating direct down-conversion of analog and digital AM and PM signals to demodulated baseband signals, and exemplary methods and systems thereof, are disclosed in the co-pending U.S. patent application entitled “Method and System for Down-Converting Electromagnetic Signals,” Ser. No. 09/176,022, filed Oct. 21, 1998.
Alternatively, to down-convert an input FM signal to a non-FM signal, a frequency within the FM bandwidth must be down-converted to baseband (i.e., zero IF). As an example, to down-convert a frequency shift keying (FSK) signal (a sub-set of FM) to a phase shift keying (PSK) signal (a subset of PM), the mid-point between a lower frequency F1 and an upper frequency F2 (that is, [(F1+F2)÷2]) of the FSK signal is down-converted to zero IF. For example, to down-convert an FSK signal having F1 equal to 899 MHz and F2 equal to 901 MHz, to a PSK signal, the aliasing rate of the control signal 6406 would be calculated as follows:
Frequency of the down-converted signal=0 (i.e., baseband)
(Freqinput−FreqIF)/n=Freqcontrol
(900 MHz−0 MHz)/n=900 MHz/n
For n=0.5, 1, 2, 3, etc., the frequency of the control signal 6406 should be substantially equal to 1.8 GHz, 900 MHz, 450 MHz, 300 MHz, 225 MHz, etc. The frequency of the down-converted PSK signal is substantially equal to one half the difference between the lower frequency F1 and the upper frequency F2.
As another example, to down-convert a FSK signal to an amplitude shift keying (ASK) signal (a subset of AM), either the lower frequency F1 or the upper frequency F2 of the FSK signal is down-converted to zero IF. For example, to down-convert an FSK signal having F1 equal to 900 MHz and F2 equal to 901 MHz, to an ASK signal, the aliasing rate of the control signal 6406 should be substantially equal to:
(900 MHz−0 MHz)/n=900 MHz/n, or
(901 MHz−0 MHz)/n=901 MHz/n.
For the former case of 900 MHz/n, and for n=0.5, 1, 2, 3, 4, etc., the frequency of the control signal 6406 should be substantially equal to 1.8 GHz, 900 MHz, 450 MHz, 300 MHz, 225 MHz, etc. For the latter case of 901 MHz/n, and for n=0.5, 1, 2, 3, 4, etc., the frequency of the control signal 6406 should be substantially equal to 1.802 GHz, 901 MHz, 450.5 MHz, 300.333 MHz, 225.25 MHz, etc. The frequency of the down-converted AM signal is substantially equal to the difference between the lower frequency F1 and the upper frequency F2 (i.e., 1 MHz).
Exemplary time domain and frequency domain drawings, illustrating down-conversion of FM signals to non-FM signals, and exemplary methods and systems thereof, are disclosed in the co-pending U.S. patent application entitled “Method and System for Down-Converting Electromagnetic Signals,” Ser. No. 09/176,022, filed Oct. 21, 1998.
In an embodiment, the pulses of the control signal 6406 have negligible apertures that tend towards zero. This makes the UFT module 6402 a high input impedance device. This configuration is useful for situations where minimal disturbance of the input signal may be desired.
In another embodiment, the pulses of the control signal 6406 have non-negligible apertures that tend away from zero. This makes the UFT module 6402 a lower input impedance device. This allows the lower input impedance of the UFT module 6402 to be substantially matched with a source impedance of the input signal 6404. This also improves the energy transfer from the input signal 6404 to the down-converted output signal 6412, and hence the efficiency and signal to noise (s/n) ratio of UFT module 6402.
Exemplary systems and methods for generating and optimizing the control signal 6406, and for otherwise improving energy transfer and s/n ratio, are disclosed in the co-pending U.S. patent application entitled “Method and System for Down-Converting Electromagnetic Signals,” Ser. No. 09/176,022, filed Oct. 21, 1998.
7. DESIGNING A TRANSMITTER ACCORDING TO AN EMBODIMENT OF THE PRESENT INVENTIONThis section (including its subsections) provides a high-level description of an exemplary process to be used to design a transmitter according to an embodiment of the present invention. The techniques described herein are also applicable to designing a frequency up-converter for any application, and for designing the applications themselves. The descriptions are contained herein for illustrative purposes and are not limiting. Alternatives (including equivalents, extensions, variations, deviations, etc., of those described herein) will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such alternatives fall within the scope and spirit of the present invention, and the invention is intended and adapted to include such alternative.
The discussion herein describes an exemplary process to be used to design a transmitter according to an embodiment of the present invention. An exemplary circuit for a transmitter of the present invention operating in the FM embodiment is shown in
Depending on the application and on the implementation, some of the design considerations may not apply. For example, and without limitation, in some cases it may not be necessary to optimize the pulse width or to include an amplifier.
7.1 Frequency of the Transmission Signal.
The first step in the design process is to determine the frequency of the desired transmission signal 5714. This is typically determined by the application for which the transmitter is to be used. The present invention is for a transmitter that can be used for all frequencies within the electromagnetic (EM) spectrum. For the examples herein, the explanation will focus on the use of the transmitter in the 900 MHz to 950 MHz range. Those skilled in the relevant art(s) will recognize that the analysis contained herein may be used for any frequency or frequency range.
7.2 Characteristics of the Transmission Signal.
Once the frequency of the desired transmission signal 5714 is known, the characteristics of the signal must be determined. These characteristics include, but are not limited to, whether the transmitter will operate at a fixed frequency or over a range of frequencies, and if it is to operate over a range of frequencies, whether those frequencies are continuous or are divided into discrete “channels.” If the frequency range is divided into discrete channels, the spacing between the channels must be ascertained. As an example, cordless phones operating in this frequency range may operate on discrete channels that are 50 KHz apart. That is, if the cordless phones operate in the 905 MHz to 915 MHz range (inclusive), the channels could be found at 905.000, 905.050, 905.100, . . . , 914.900, 914.950, and 915.000.
7.3 Modulation Scheme.
Another characteristic that must be ascertained is the desired modulation scheme that is to be used. As described above in sections 2.1-2.2.4, above, these modulation schemes include FM, PM, AM, etc., and any combination or subset thereof, specifically including the widely used “I/Q” subset of PM. Just as the frequency of the desired transmission signal 5714 is typically determined by the intended application, so too is the modulation scheme.
7.4 Characteristics of the Information Signal.
The characteristics of an information signal 5702 are also factors in the design of the transmitter circuit. Specifically, the bandwidth of the information signal 5702 defines the minimum frequency for an oscillating signal 5704, 5738, 5744 (for the FM, PM, and AM modes, respectively).
7.5 Characteristics of the Oscillating Signal.
The desired frequency of the oscillating signal 5704, 5738, 5744 is also a function of the frequency and characteristics of the desired transmission signal 5714. Also, the frequency and characteristics of the desired transmission signal 5714 are factors in determining the pulse width of the pulses in a string of pulses 5706. Note that the frequency of the oscillating signal 5704, 5738, 5744 is substantially the same as the frequency of the string of pulses 5706. (An exception, which is discussed below, is when a pulse shaping circuit 5722 increases the frequency of the oscillating signal 5704, 5738, 5744 in a manner similar to that described above in section 4.3.2.) Note also that the frequency and pulse width of the string of pulses 5706 is substantially the same as the frequency and pulse width of a harmonically rich signal 5708.
7.5.1 Frequency of the Oscillating Signal.
The frequency of the oscillating signal 5704, 5738, 5744 must be a subharmonic of the frequency of the desired transmission signal 5714. A subharmonic is the quotient obtained by dividing the fundamental frequency, in this case the frequency of the desired transmission signal 5714, by an integer. When describing the frequency of certain signals, reference is often made herein to a specific value. It is understood by those skilled in the relevant art(s) that this reference is to the nominal center frequency of the signal, and that the actual signal may vary in frequency above and below this nominal center frequency based on the desired modulation technique being used in the circuit. As an example to be used herein, if the frequency of the desired transmission signal is 910 MHz, and it is to be used in an FM mode where, for example, the frequency range of the modulation is 40 KHz, the actual frequency of the signal will vary ±20 KHz around the nominal center frequency as a function of the information being transmitted. That is, the frequency of the desired transmission signal will actually range between 909.980 MHz and 910.020 MHz.
The first ten subharmonics of a 910.000 MHz signal are given below.
The oscillating signal 5704, 5738, 5744 can be at any one of these frequencies or, if desired, at a lower subharmonic. For discussion herein, the 9th subharmonic will be chosen. Those skilled in the relevant art(s) will understand that the analysis herein applies regardless of which harmonic is chosen. Thus the nominal center frequency of the oscillating signal 5704, 5738, 5744 will be 101.1111 MHz. Recalling that in the FM mode, the frequency of the desired transmission signal 5714 is actually 910.000 MHz±0.020 MHz, it can be shown that the frequency of the oscillating signal 5704 will vary ±0.00222 MHz (i.e., from 101.10889 MHz to 101.11333 MHz). The frequency and frequency sensitivity of the oscillating signal 5704 will drive the selection or design of the voltage controlled oscillator (VCO) 5720.
Another frequency consideration is the overall frequency range of the desired transmission signal. That is, if the transmitter is to be used in the cordless phone of the above example and will transmit on all channels between 905 MHz and 915 MHz, the VCO 5720 (for the FM mode) or the local oscillator (LO) 5734 (for the PM and AM modes) will be required to generate oscillating frequencies 5704, 5738, 5744 that range from 100.5556 MHz to 101.6667 MHz. (That is, the 9th subharmonic of 910 MHz±5 MHz). In some applications, such as the cellular phone, the frequencies will change automatically, based on the protocols of the overall cellular system (e.g., moving from one cell to an adjacent cell). In other applications, such as a police radio, the frequencies will change based on the user changing channels.
In some applications, different models of the same transmitter will transmit signals at different frequencies, but each model will, itself, only transmit a single frequency. A possible example of this might be remote controlled toy cars, where each toy car operates on its own frequency, but, in order for several toy cars to operate in the same area, there are several frequencies at which they could operate. Thus, the design of the VCO 5720 or LO 5734 will be such that it is able to be tuned to a set frequency when the circuit is fabricated, but the user will typically not be able to adjust the frequency.
It is well known to those skilled in the relevant art(s) that several of the criteria to be considered in the selection or design of an oscillator (VCO 5720 or LO 5734) include, but are not limited to, the nominal center frequency of the desired transmission signal 5714, the frequency sensitivity caused by the desired modulation scheme, the range of all possible frequencies for the desired transmission signal 5714, and the tuning requirements for each specific application. Another important criterion is the determination of the subharmonic to be used, but unlike the criteria listed above which are dependent on the desired application, there is some flexibility in the selection of the subharmonic.
7.5.2 Pulse Width of the String of Pulses.
Once the frequency of the oscillating signal 5704, 5738, 5744 has been selected, the pulse width of the pulses in the stream of pulses 5706 must be determined. (See sections 4-4.3.4, above, for a discussion of harmonic enhancement and the impact the pulse-width-to-period ratio has on the relative amplitudes of the harmonics in a harmonically rich signal 5708.) In the example used above, the 9th subharmonic was selected as the frequency of the oscillating signal 5704, 5738, 5744. In other words, the frequency of the desired transmission signal will be the 9th harmonic of the oscillating signal 5704, 5738, 5744. One approach in selecting the pulse width might be to focus entirely on the frequency of the oscillating signal 5704, 5738, 5744 and select a pulse width and observe its operation in the circuit. For the case where the harmonically rich signal 5708 has a unity amplitude, and the pulse-width-to-period ratio is 0.1, the amplitude of the 9th harmonic will be 0.0219. Looking again at Table 6000 and
Looking at Eq. 1 in section 4.1.1, it is seen that the relative amplitude of any harmonic is a function of the number of the harmonic and the pulse-width-to-period ratio of the underlying waveform. Applying calculus of variations to the equation, the pulse-width-to-period ratio that yields the highest amplitude harmonic for any given harmonic can be determined.
From Eq. 1, where An is the amplitude of the nth harmonic,
An=[Apulse][(2/π)/n] sin {n·π·(τ/T)] Eq. 2
If the amplitude of the pulse, Apulse, is set to unity (i.e., equal to 1), the equation becomes
An=[2/(n·π)] sin [n·π·(τ/T)] Eq. 3
From this equation, it can be seen that for any value of n (the harmonic) the amplitude of that harmonic, An, is a function of the pulse-width-to-period ratio, τ/T. To determine the highest value of An for a given value of n, the first derivative of An with respect to τ/T is taken. This gives the following equations.
From calculus of variations, it is known that when the first derivative is set equal to zero, the value of the variable that will yield a relative maximum (or minimum) can be determined.
δ(An)/δ(τ/T)=0 Eq. 7
[2/(n·π)] cos [n·π·(τ/T)]=0 Eq. 8
cos [n·π·(τ/T)]=0 Eq. 9
From trigonometry, it is known that for Eq. 9 to be true,
n·π·(τ/T)=π/2 (or 3π/2, 5π/2, etc.) Eq. 10
τ/T=(π/2)/(n·π) Eq. 11
τ/T=1/(2·n) (or 3/(2·n), 5/(2·n), etc.) Eq. 12
The above derivation is well known to those skilled in the relevant art(s). From Eq. 12, it can be seen that if the pulse-width-to-period ratio is equal to 1/(2·n), the amplitude of the harmonic should be substantially optimum. For the case of the 9th harmonic, Eq. 12 will yield a pulse-width-to-period ratio of 1/(2·9) or 0.0556. For the amplitude of this 9th harmonic, Table 6100 of
This is one approach to determining the desired pulse-width-to-period ratio. Those skilled in the relevant art(s) will understand that other techniques may also be used to select a pulse-width-to-period ratio.
7.6 Design of the Pulse Shaping Circuit.
Once the determination has been made as to the desired frequency of the oscillating signal 5704, 5738, 5744 and of the pulse width, the pulse shaping circuit 5722 can be designed. Looking back to sections 4-4.3.4 it can be seen that the pulse shaping circuit 5722 can not only produce a pulse of a desired pulse width, but it can also cause the frequency of the string of pulses 5706 to be higher than the frequency of the oscillating signal 5704, 5738, 5744. Recall that the pulse-width-to-period ratio applies to the pulse-width-to-period ratio of the harmonically rich signal 5708 and not to the pulse-width-to-period ratio of the oscillating signal 5704, 5738, 5744, and that the frequency and pulse width of the harmonically rich signal 5708 mirrors the frequency and pulse width of the string of pulses 5706. Thus, if in the selection of the VCO 5720 or LO 5734 it was desired to choose an oscillator that is lower than that required for the selected harmonic, the pulse shaping circuit 5733 can be used to increase the frequency. Going back to the previous example, the frequency of the oscillating signal 5704, 5738, 5744 could be 50.5556 MHz rather than 101.1111 MHz if the pulse shaping circuit 5722 was designed such as discussed in sections 4.2.2-4.2.2.2 (shown in
It should also be understood that the pulse shaping circuit 5722 is not always required. If the design or selection of the VCO 5720 or LO 5734 was such that the oscillating signal 5704, 5738, 5744 was a substantially rectangular wave, and that substantially rectangular wave had a pulse-width-to-period ratio that was adequate, the pulse shaping circuit 5722 could be eliminated.
7.7 Selection of the Switch.
The selection of a switch 5724 can now be made. The switch 5724 is shown in the examples of
7.7.1 Optimized Switch Structures.
Switches of Different SizesIn an embodiment, the switch modules discussed herein can be implemented as a series of switches operating in parallel as a single switch. The series of switches can be transistors, such as, for example, field effect transistors (FET), bi-polar transistors, or any other suitable circuit switching devices. The series of switches can be comprised of one type of switching device, or a combination of different switching devices.
For example,
In an embodiment, FETs 7302a-n have similar characteristics. In another embodiment, one or more of FETs 7302a-n have different characteristics than the other FETs. For example, FETs 7302a-n may be of different sizes. In CMOS, generally, the larger size a switch is (meaning the larger the area under the gate between the source and drain regions), the longer it takes for the switch to turn on. The longer turn on time is due in part to a higher gate to channel capacitance that exists in larger switches. Smaller CMOS switches turn on in less time, but have a higher channel resistance. Larger CMOS switches have lower channel resistance relative to smaller CMOS switches. Different turn on characteristics for different size switches provides flexibility in designing an overall switch module structure. By combining smaller switches with larger switches, the channel conductance of the overall switch structure can be tailored to satisfy given requirements.
In an embodiment, FETs 7302a-n are CMOS switches of different relative sizes. For example, FET 7302a may be a switch with a smaller size relative to FETs 7302b-n. FET 7302b may be a switch with a larger size relative to FET 7302a, but smaller size relative to FETs 7302c-n. The sizes of FETs 7302c-n also may be varied relative to each other. For instance, progressively larger switch sizes may be used. By varying the sizes of FETs 7302a-n relative to each other, the turn on characteristic curve of the switch module can be correspondingly varied. For instance, the turn on characteristic of the switch module can be tailored such that it more closely approaches that of an ideal switch. Alternately, the switch module could be tailored to produce a shaped conductive curve.
By configuring FETs 7302a-n such that one or more of them are of a relatively smaller size, their faster turn on characteristic can improve the overall switch module turn on characteristic curve. Because smaller switches have a lower gate to channel capacitance, they can turn on more rapidly than larger switches.
By configuring FETs 7302a-n such that one or more of them are of a relatively larger size, their lower channel resistance also can improve the overall switch module turn on characteristics. Because larger switches have a lower channel resistance, they can provide the overall switch structure with a lower channel resistance, even when combined with smaller switches. This improves the overall switch structure's ability to drive a wider range of loads. Accordingly, the ability to tailor switch sizes relative to each other in the overall switch structure allows for overall switch structure operation to more nearly approach ideal, or to achieve application specific requirements, or to balance trade-offs to achieve specific goals, as will be understood by persons skilled in the relevant arts(s) from the teachings herein.
It should be understood that the illustration of the switch module as a series of FETs 7302a-n in
Circuit performance also can be improved by reducing overall switch area. As discussed above, smaller switches (i.e., smaller area under the gate between the source and drain regions) have a lower gate to channel capacitance relative to larger switches. The lower gate to channel capacitance allows for lower circuit sensitivity to noise spikes.
It should be understood that the illustration of the switches above as FETs in
In embodiments wherein the switch modules discussed herein are comprised of a series of switches in parallel, in some instances it may be desirable to minimize the effects of charge injection. Minimizing charge injection is generally desirable in order to reduce the unwanted circuit radiation resulting therefrom. In an embodiment, unwanted charge injection effects can be reduced through the use of complementary n-channel MOSFETs and p-channel MOSFETs. N-channel MOSFETs and p-channel MOSFETs both suffer from charge injection. However, because signals of opposite polarity are applied to their respective gates to turn the switches on and off, the resulting charge injection is of opposite polarity. As a result, n-channel MOSFETs and p-channel MOSFETs may be paired to cancel their corresponding charge injection. Hence, in an embodiment, the switch module may be comprised of n-channel MOSFETs and p-channel MOSFETS, wherein the members of each are sized to minimize the undesired effects of charge injection.
It should be understood that the use of FETs in
The processes involved in fabricating semiconductor circuits, such as MOSFETs, have limitations. In some instances, these process limitations may lead to circuits that do not function as ideally as desired. For instance, a non-ideally fabricated MOSFET may suffer from parasitic capacitances, which in some cases may cause the surrounding circuit to radiate noise. By fabricating circuits with structure layouts as close to ideal as possible, problems of non-ideal circuit operation can be minimized.
Operation of MOSFET 7600 shall now be described. When a positive voltage is applied to gate 7602, electrons in the p-type material of channel region 7604 are attracted to the surface below insulator 7614, forming a connecting near-surface region of n-type material between the source and the drain, called a channel. The larger or more positive the voltage between the gate contact 7606 and source region 7608, the lower the resistance across the region between.
In
As shown in
It should be understood that the illustration of the n-channel enhancement-mode MOSFET is for example purposes only. The present invention is applicable to depletion mode MOSFETs, and other transistor types, as will be apparent to persons skilled in the relevant art(s) based on the discussion contained herein.
7.7.2 Phased D2D—Splitter in CMOS.
I-channel flip-flop 7212 inputs inverted LO signal 7218. Q-channel flip-flop 7214 inputs non-inverted LO signal 7220. In the current embodiment, I-channel flip-flop 7212 and Q-channel flip-flop 7214 are edge-triggered flip-flops. When either flip-flop receives a rising edge on its input, the flip-flop output changes state. Hence, I-channel flip-flop 7212 and Q-channel flip-flop 7214 each output signals that are approximately half of the input signal frequency. Additionally, as would be recognized by persons skilled in the relevant art(s), because the inputs to I-channel flip-flop 7212 and Q-channel flip-flop 7214 are approximately 180° out of phase, their resulting outputs are signals that are approximately 90° out of phase. I-channel flip-flop 7212 outputs I-channel oscillating signal 7222, as shown in
It should be understood that the illustration of the splitter circuit 7200 in
7.8 Design of the Filter.
The design of the filter 5726 is determined by the frequency and frequency range of the desired transmission signal 5714. As discussed above in sections 3.3.9-3.3.9.2, the term “Q” is used to describe the ratio of the center frequency of the output of the filter to the bandwidth of the “3 dB down” point. The trade offs that were made in the selection of the subharmonic to be used is a factor in designing the filter. That is, if, as an excursion to the example given above, the frequency of the desired transmission signal were again 910 MHz, but the desired subharmonic were the 50th subharmonic, then the frequency of that 50th subharmonic would be 18.2000 MHz. This means that the frequencies seen by the filter will be 18.200 MHz apart. Thus, the “Q” will need to be high enough to avoid allowing information from the adjacent frequencies being passed through. The other consideration for the “Q” of the filter is that it must not be so tight that it does not permit the usage of the entire range of desired frequencies.
7.9 Selection of an Amplifier.
An amplifier module 5728 will be needed if the signal is not large enough to be transmitted or if it is needed for some downstream application. This can occur because the amplitude of the resultant harmonic is too small. It may also occur if the filter 5726 has attenuated the signal.
7.10 Design of the Transmission Module.
A transmission module 5730, which is optional, ensures that the output of the filter 5726 and the amplifier module 5728 is able to be transmitted. In the implementation wherein the transmitter is used to broadcast EM signals over the air, the transmission module matches the impedance of the output of the amplifier module 5728 and the input of an antenna 5732. This techniques is well known to those skilled in the relevant art(s). If the signal is to be transmitted over a point-to-point line such as a telephone line (or a fiber optic cable) the transmission module 5730 may be a line driver (or an electrical-to-optical converter for fiber optic implementation).
Claims
1. A system for modulating and up-converting an information signal, comprising:
- gating means for gating the information signal at a rate that is substantially equal to a desired sub-harmonic of a desired frequency of an output signal, thereby generating a gated information signal, said gated information signal having an amplitude that is a function of the information signal;
- differentiating means for differentiating said gated information signal to generate a harmonically rich signal having a plurality of harmonics; and
- selecting means for selecting at least one of said plurality of harmonics as a desired output signal, said desired output signal being at said desired frequency.
Type: Application
Filed: Jul 16, 2012
Publication Date: May 16, 2013
Applicant: PARKERVISION, INC. (Jacksonville, FL)
Inventors: David F. Sorrells (Jacksonville, FL), Michael J. Bultman (Jacksonville, FL), Robert W. Cook (Switzerland, FL), Richard C. Looke (Jacksonville, FL), Charley D. Moses, JR. (Jacksonville, FL)
Application Number: 13/550,492
International Classification: H04B 1/04 (20060101);