Abstract: A transmitter generates first and second constant-envelope radio frequency (RF) component signals having first and second phase angles. The first and second phases are controlled by a phase controller. First and second nonlinear power amplifiers (PAs) are modulated by an amplitude-modulated power supply signal as the first and second constant-envelope RF component signals are amplified. The phase controller controls the first and second phases of the first and second constant-envelope RF component signals, in response to a power control signal, and, in so doing, controls an effective load impedance seen at the outputs of the first and second nonlinear PAs. By controlling the effective load impedance in response to a power control signal, rather than in response to rapid amplitude variations in an input signal envelope, the output power of the transmitter is efficiently controlled over a wide dynamic range even at low output powers.

Abstract: A transmission device of the present invention comprises: an orthogonal modulator performing orthogonal modulation on a carrier wave using an input signal comprising an in-phase signal component and an orthogonal signal component, and outputs a modulation signal to be transmitted; a detection unit detecting a carrier leaking component included in the modulation signal; a DC offset value computing unit computing a DC offset value to be added to the input signal for compensating the carrier leaking component, based on the carrier leaking component; and an abnormality judgment unit judging abnormality of the orthogonal modulator based on the DC offset value. By monitoring the DC offset value, a failure of the orthogonal modulator or an indication thereof is detected, and transmission of an abnormal modulation signal including a distortion component is prevented. An increase of the leaking power to adjacent channels, which causes the quality deterioration in adjacent radio communication lines, can be prevented.

Abstract: Apparatus and methods for adjustment of spectral signal characteristics in polar modulators are described. A composite signal detection circuit is configured to detect when a signal trajectory of a composite signal provided to the polar modulator passes near the origin of a complex plane associated with the composite signal, and then adjusts the composite signal to pass through the origin. A spectral adjustment circuit is described to adjust AM and FM or PM components of the composite signal to reduce the deviation of an FM component of the composite signal.

Abstract: A method for modulating a signal transmitted by a first device to a second device which is energised by the signal, wherein the first device is further arranged to amplitude modulate the signal so as to transmit data thereon, the method further comprising phase modulating the signal.

Abstract: A transmitting apparatus and method for power amplification with delay control in a wireless communication system are provided. The apparatus includes signal converters, a delay difference measurer, and a delay controller. The signal converters separate a baseband signal into an envelope signal and a phase modulated signal. The delay difference measurer measures a delay difference between an envelope signal path and a phase modulated signal path using a correlation coefficient extraction and interpolation technique. The delay controller sets a delay in a clock period unit to a signal path having a small delay and sets a delay by a remainder delay difference to a signal path having a large delay, depending on the measured delay difference.

Abstract: An embodiment of the present invention provides transmitter having a phase locked loop that has a dynamically controllable loop bandwidth. A transmit modulator is coupled to the PLL for performing vector modulation in response to transmission symbols. Each transmission symbol comprises an amplitude signal and a phase signal. A controller is coupled to the PLL and to the transmit modulator and is operable to detect when a criteria of the transmission symbols crosses a threshold and to adjust loop bandwidth in response to crossing the threshold. The criteria of the transmission symbols may be a function of the amplitude signal or a function of the phase signal, and may be the amplitude signal, a first derivative of the amplitude signal, a second derivative of the amplitude signal, a square of the amplitude signal, a derivative of the amplitude signal squared, the phase signal, or a derivative of the phase signal.

Abstract: An amplitude modulation circuit in a polar transmitter includes a digital-to-analog converter (DAC), a filter, a gm stage, and a calibration module. The DAC is arranged to be coupled to an amplitude modulation signal input in a normal mode. The filter is coupled to the DAC, and the gm stage is coupled to the filter. The calibration module has an input coupled to the gm stage, and an output coupled to a node on a path between the DAC and the gm stage. A method for calibrating an amplitude offset in the polar transmitter includes: generating an amplitude offset calibration signal according to an amplitude modulation signal generated from the gm stage; and transmitting the amplitude offset calibration signal via the output of the calibration module to a node on a path between the DAC and the gm stage so as to calibrate the amplitude offset.

Abstract: An RF transmitter includes a Cartesian to polar conversion section, a PLL, a DAC module, a mixing module, and a PA module. The Cartesian to polar conversion section converts a Cartesian based symbol stream into a polar based symbol stream. The PLL generates an oscillation when the RF transmitter is in a Cartesian mode or a phase modulated oscillation based on phase modulation information of the polar based symbol stream when the RF transmitter is in a polar mode. The mixing module mixes an analog Cartesian based signal with a local oscillation to produce a Cartesian based up converted signal when the RF transmitter is in the Cartesian mode and mixes an analog amplitude signal with a phase modulated local oscillation to produce a polar based up converted signal when the RF transmitter is in the polar mode.

Abstract: In a system with an intermittently operating radio, the frequency of which is controlled by a Phase Locked Loop (PLL), a method and system for reducing the power consumed by the PLL by tri-stating the control capacitor in the PLL after the PLL has stabilized at a design frequency. After the capacitor is stabilized, power to some of the components in the PLL is reduced.

Abstract: The present invention relates to a polar transmission method and a polar transmitter for transmitting phase and amplitude components derived from in-phase (I) and quadrature-phase (Q) components of an input signal. A first conversion is provided for converting the in-phase (I) and quadrature-phase (Q) components into the phase and amplitude components at a first sampling rate. Additionally, a second conversion is provided for converting the phase component into a frequency component, wherein the second conversion comprises a rate conversion for converting the first sampling rate into a lower second sampling rate at which the frequency component is provided. Thereby, the second sampling rate can be used as a lower update rate in a digitally controlled oscillator in order to save power or because of speed limitations, while the surplus phase samples obtain due to the higher first sampling rate enable better approximation of the phase component after the digitally controlled oscillator.

Abstract: A multiple-mode modulator is configured similarly to a direct conversion quadrature modulator with an infusion of an amplitude modulation signal path from a large signal polar modulator to improve the power amplifier efficiency. The multiple-mode modulator also includes a radio frequency signal path. The multiple-mode modulator is configured to receive a baseband signal, convert the baseband signal to a radio frequency (RF) signal, and to process the RF signal according to either a polar mode or a quadrature mode, depending on a time-varying input voltage of the RF signal. When the power amplifier operates in the linear region, the RF signal is processed according to the quadrature mode. When the power amplifier operates in the compressed region, the RF signal is processed according to the polar mode. The multiple-mode modulator can be configured according to a small signal polar architecture or a large signal polar architecture, having either an open-loop or closed-loop configuration.

Abstract: A system for calibrating a closed power control loop includes an adder configured to inject a test signal into an adjustable element, a first peak detector configured to determine an amplitude of the injected test signal, a second peak detector configured to determine an amplitude of a return test signal, a comparator configured to determine the difference between the injected test signal and the return test signal, and a calibration engine configured to adjust the adjustable element so that the return test signal is offset from the injected test signal by a predetermined amount.

Abstract: An amplitude modulation circuit in a polar transmitter and a method for calibrating amplitude offset in the polar transmitter are provided. The amplitude modulation circuit includes a digital-to-analog converter (DAC), a low pass filter (LPF), a gm stage, and a calibration module. The DAC is coupled to an amplitude modulation signal input. The LPF is coupled to the DAC, and the gm stage is coupled to the LPF. The calibration module has an input coupled to the gm stage, and an output coupled to a node on a path between the DAC and the gm stage. The method includes: generating an amplitude offset calibration signal according to an amplitude modulation signal generated from the gm stage; and transmitting the amplitude offset calibration signal via the output of the calibration module to a node on a path between the DAC and the gm stage so as to calibrate the amplitude offset.

Abstract: An apparatus including a spin torque oscillator configured to receive an input electric current and to produce a radio frequency output signal; and a tunable current source for providing an input electric current to the spin torque oscillator.

Abstract: Provided is a transmission circuit capable of operating with high linearity and with low noise. An AM variable fc filter uses an AM cutoff frequency to remove a high frequency component from an amplitude signal. An amplifier supplies a power amplifier with a voltage which is a result of amplifying the amplitude signal outputted from the AM variable fc filter. A PM variable fc filter uses a PM cutoff frequency to remove a high frequency component from a phase signal. A phase modulator phase-modulates the phase signal outputted from the PM variable fc filter to output a high-frequency phase-modulated signal. The power amplifier amplifies the high-frequency phase-modulated signal by using the voltage supplied from the amplifier, and outputs a resultant signal as a transmission signal.

Abstract: A feedback loop is used to determine phase distortion created in a signal by directly extracting the phase distortion information from a feedback signal using original frequency modulation information.

Abstract: An integrated circuit (IC) includes a baseband processing module and a radio frequency (RF) section. The baseband processing module is coupled to convert outbound data or an outbound voice signal into at least one of amplitude modulation information, phase modulation information, and frequency modulation information. The RF section includes an oscillation module, a frequency divider, and power amplifier modules. The oscillation module produces an RF oscillation that it modulates based on the phase or frequency modulation information to produce a modulated RF signal. The frequency divider divides the frequency of the modulated RF signal to produce a frequency divided modulated RF signal. The first power amplifier module amplifies the modulated RF signal in accordance with the amplitude modulation information or a constant to produce a first frequency band outbound RF data or voice signal.

Abstract: Exemplary embodiments are directed to forward link signaling via transmitter detuning A method may include selectively detuning a circuit to adjust an amplitude of an associated transmit signal based on data to be transmitted. The method may also include selectively retuning the circuit to differently adjust the amplitude of the transmit signal based on the data to be transmitted.

Abstract: A power amplifier controller circuit controls a power amplifier based upon an amplitude correction signal indicating the amplitude difference between the amplitude of the input signal and an attenuated amplitude of the output signal. The power amplifier controller circuit comprises an amplitude control loop and a phase control loop. The amplitude control loop adjusts the supply voltage to the power amplifier based upon the amplitude correction signal. The RF power amplifier system may reduce the corrective action of the amplitude loop during periods of relatively rapid changes in amplitude, and thus distortion can be further reduced.

Abstract: An integrated circuit (IC) includes a baseband processing module and a radio frequency (RF) section. The baseband processing module is coupled to convert outbound data into amplitude modulation information and phase modulation information when the IC is in a cellular data mode and to convert an outbound radio frequency identification (RFID) signal into RFID amplitude modulation information when the IC is in an RFID mode. The RF section is coupled to generate an outbound RF data signal in accordance with the amplitude modulation information and the phase modulation information when the IC is in the cellular data mode and to generate an outbound RF RFID signal in accordance with the RFID amplitude information when the IC is in the RFID mode.

Abstract: The present invention relates to estimating a direct current (DC) offset of a power detection circuit when an estimated instantaneous amplitude of a continuous-transmission amplitude-modulated (AM) radio frequency (RF) signal is below a first threshold. The power detection circuit may be used to estimate an average output power associated with the continuous-transmission AM RF signal. The estimated average output power may be used as part of a feedback system to regulate the average output power. The estimated DC offset of the power detection circuit may be used to improve the estimate of the average output power, particularly over temperature and supply voltage variations. Estimating the DC offset of the power detection circuit when the estimated instantaneous amplitude of the continuous-transmission AM RF signal is below the first threshold may minimize errors in the estimated DC offset.

Abstract: A wireless network connection system remotely connects to a network without the use of crystal reference oscillators. This provides communication at long range using a low transmit Effective Isotropic Radiated Power (EIRP). Operation is obtained through a combination of injection locking the system clock to the fundamental frequency of a remote reference oscillator, injection locking the transmitter to the third harmonic of the remote reference oscillator, a micro-watt RF receiver, and a network connection.

Abstract: A signal scaling device (D), for a transmission path of a wireless communication equipment, comprises a processing means (PM) adapted to receive a phase and/or amplitude modulated signal (I/Q) to transmit, and arranged to multiply said phase and/or amplitude modulated signal with a chosen complex gain in order to output said phase and/or amplitude modulated signal with a chosen scaled amplitude and a chosen phase offset.

Abstract: Methods and apparatus for reconstructing discrete-time amplitude modulation signals in polar modulation transmitters. An exemplary polar modulation transmitter includes a symbol generator, a rectangular-to-polar converter, a peak phase detector, and an amplitude modulation reconstruction circuit. The symbol generator generates rectangular-coordinate modulation symbols from which the rectangular-to-polar converter generates an amplitude modulation signal containing discrete-time amplitude samples and an angle modulation signal containing discrete-time angle samples. The peak phase detector circuit detects phase reversals or near phase reversals represented in samples of the angle modulation signal. The amplitude modulation reconstruction circuit responds by reconstructing samples in the amplitude modulation signal that correspond to detected phase reversals or a near phase reversals represented in samples of the angle modulation signal.

Abstract: Data encoded in packets modulated onto a carrier wave is transmitted between a base station and a transponder. Each packet includes a header section that contains at least a reference symbol and that serves for adjusting one or more transmission parameters, and a further section such as a data section. The transponder transmits data back to the base station through modulation and backscattering of the carrier wave. During the transmission of the header section by the base station, the transponder transmits transponder operating information relating to the processing of data to be received and/or transmitted by the transponder, by corresponding modulation and backscattering of the carrier wave. In response to and dependent on the received transponder operating information, the base station adjusts at least one transmission parameter, whereby the highest data transmission rate within the capabilities of the particular transponder can be achieved.

Abstract: Amplitude modulation is provided for a polar transmitter that incorporates a translational loop. The input to the polar transmitter and translational loop may be an amplitude modulated signal. The amplitude modulation of the transmitter may be controlled via a closed loop to help ensure that the output of the amplifier accurately corresponds to the modulated input signal. The transmitter may incorporate partially integrated or separate translational and amplitude modulation loops.

Abstract: An apparatus for wireless communications is disclosed including a signal generator adapted to generate a substantially periodic signal including a plurality of cycles, and a modulator adapted to modulate an amplitude, a phase or both the amplitude and the phase of the periodic signal on a per cycle basis. In one aspect, the modulator is adapted to modulate the amplitude, the phase, or both the amplitude and phase of the periodic signal with a defined modulation signal. In another aspect, the defined modulation signal includes a substantially root raised cosine signal. In yet another aspect, the defined modulation signal is configured to achieve a defined frequency spectrum for the modulated periodic signal.

Abstract: Systems and methods are disclosed for an electronically adjustable signal filter system, which comprises, in some embodiments, a first filter coupled to an antenna coupling network and a second filter, a power amplifier coupled to the first filter, an antenna connected to an antenna coupling network, a pilot tone generator coupled to the first filter, and a first signal source connected to the power amplifier and first filter. In some embodiments, the power amplifier amplifies the first signal, the first filter places a notch into the first signal transmitted to the antenna coupling network, the antenna coupling network combines the first signal and a second signal received from the antenna and transmits a third signal to the second filter.

Abstract: According to one exemplary embodiment, a method for producing an up-converted and amplified transmission signal comprises performing a logarithmic transformation of an input transmission signal to form a logarithmically transformed transmission signal, adding the logarithmically transformed transmission signal to a logarithmic local oscillator signal to form a sum signal, and performing an antilogarithmic transformation of the sum signal to produce the up-converted and amplified transmission signal. In one embodiment, a log-antilog circuit for producing an up-converted and an amplified transmission signal comprises a transmission log block configured to receive an input transmission signal and to provide a logarithmically transformed transmission signal as a transmission log block output, and an antilog block coupled to the transmission log block. The antilog block is configured to receive a sum signal of the transmission log block output and a logarithmic local oscillator signal.

Abstract: Envelope tracking (ET) methods and systems for controlling the delivery of power to radio frequency power amplifiers (RFPAs). An exemplary ET system includes an RFPA and a wide bandwidth capable and power efficient envelope modulator that includes a first power supplying apparatus and a second power supplying apparatus. The first power supplying apparatus includes a switch-mode converter and a regulator. The first mode converter is operable to dynamically step down a fixed power supply voltage according to amplitude variations in an envelope signal received by the regulator, and use the resulting dynamic power supply signal to power the regulator. The second power supplying apparatus is connected in parallel with the first power supplying apparatus. Depending on a power of an output signal to be generated at an output of the power amplifier, power is supplied to the power amplifier from either or both of the first and second power supplying apparatuses.

Abstract: A polar modulator including a signal converter configured to provide a phase signal and an amplitude signal based on at least one received signal is disclosed. A digital-to-analog converter is coupled to the signal converter, the digital-to-analog converter configured to receive an augmented signal, wherein a polarity of the augmented signal is selected to minimize an absolute phase change for sequential signals. A signal mixer is coupled to the digital-to-analog converter to receive an analog signal generated from the augmented signal.

Abstract: A signal transmission apparatus of the invention comprises: a correlator 12 for shaping a spectrum of a signal; and a precoder 12 disposed on a previous stage of the correlator and including an adder which subtracts an output signal of a feedback filter from an input signal, a modulo arithmetic unit which inputs an output signal of the adder and executes modulo arithmetic operation, and the feedback filter which inputs an output signal of the modulo arithmetic unit and is provided with a transfer function obtained by subtracting 1 from a transfer function of the correlator. The correlator may be IIR filter means having a desired notch characteristic. By disposing a correlator which can freely shape a transmission signal spectrum containing a deep notch and suppress only a specified band on a receiving side, the suppression of an external noise can also be realized.

Abstract: A wireless communication device including: a transmitter including two DA converter units which convert two digital signals into analog signals; a combiner which combines the analog signals; a distributor which extracts a portion of the combined signal as a feedback signal; an AD converter which converts the feedback signal; an oscillator unit which supplies clock signals to operate the DA converter units and the AD converter; a first separation unit which separates the feedback signal converted by the AD converter into two signals; and a comparator unit which compares at least one of the two digital signals that are obtained by separating the inputted digital signal, or, at least one of the two digital signals that are separately inputted, with the feedback signal separated by the first separation unit, wherein the oscillator unit controls the output clock signals based on a result of the comparison by the comparator unit.

Abstract: A transmitting unit (12) clips a communication signal (14) to form a threshold-responsive signal (36, 36?) which includes in-band distortion (40) and out-of-band distortion (38). A portion of the out-of-band distortion (38) is notched within rejection bands (48, 50) adjacent to the communication signal's bandwidth (24). But remaining portions of the out-of-band distortion (38) and portions of the in-band distortion (40) are included with the communication signal (14). The remaining portion of the out-of-band distortion (38) causes the communication signal (14) to be in violation of a spectral mask (30). The mask-violating communication signal 14 with out-of-band distortion (38) and in-band distortion (40) is amplified by an RF power amplifier (22). After amplification, a bandpass filter (92) exhibiting fast rolloff regions (110) attenuates the amplified out-of-band distortion (38) causing compliance with the spectral mask (30).

Abstract: Apparatus is presented for broadcasting an RF signal. This includes a signal divider that receives a composite RF signal and provides therefrom first and second signals each having digital and analog components. A phase extractor receives the first signal and provides therefrom a phase modulated RF signal for application to an amplifier. A gain controller varies the gain of the amplifier in accordance with amplitude variations of the second signal.

Abstract: A transmission circuit capable of transmitting a modulated wave signal using polar modulation in a broad band and with low power consumption is provided. The transmission circuit generates an amplitude signal and a phase signal based on data to be transmitted, and separates the amplitude signal into a low-frequency amplitude signal and a high-frequency amplitude signal. The transmission circuit amplitude-modulates the phase signal in a broad band using the high-frequency amplitude signal in a high-frequency voltage control section 104 and an amplitude modulation section 105 and amplitude-modulates the phase signal into low power consumption using the low-frequency amplitude signal in a low-frequency voltage control section 106 and amplitude modulation section 107.

Abstract: The invention relates to methods for transmitting and receiving a data bit stream in a communication system using a 16-QAM constellation. Further, an apparatus for performing the methods is provided. To provide a modulation and coding scheme using a signal space expansion and 16-QAM which improves the bit-error rate in comparison to QPSK modulated signals and still provides the possibility to implement coders and decoders with low complexity the invention suggests the use a 16-QAM constellation with specially selected mapping rules together with repetition coding (signal space expansion) and interleaving of the data stream to be transmitted.

Abstract: A real-time/non-real-time/RF IC includes first and second baseband processing modules, an RF section, a wireline interface, and a bus structure. The first baseband processing module converts real-time outbound data into real-time outbound symbols and converts real-time inbound symbols into real-time inbound data. The second baseband processing module converts non-real-time outbound data into non-real-time outbound symbols and converts non-real-time inbound symbols into non-real-time inbound data. The RF section converts the real-time outbound symbols into real-time outbound RF signals, converts real-time inbound RF signals into the real-time inbound symbols, converts the non-real-time outbound symbols into non-real-time outbound RF signals, and converts non-real-time inbound RF signals into the non-real-time symbols. The wireline interface couples the non-real-time outbound data, the non-real-time inbound data, the real-time outbound data, and/or the real-time inbound data to an off-chip wireline connection.

Abstract: Previously, when designing receivers for radio frequency (RF) or wireless communications, designers chose between time-interleaved (TI) analog-to-digital converters (ADCs) for intermediate frequency architectures and dual channel ADCs for direct conversion architectures. Here, similarities between TI ADCs and dual channel ADC were recognized, and an ADC that has the capability of operating as a TI ADCs and dual channel ADC is provided. This allows designer to have greatly increased flexibility during the design process which can greatly reduce design costs, while also allowing the manufacturer of the ADC to realize a reduction in its operating costs.

Abstract: A data communication system that enhances concealment by significantly increasing the time required for a wiretapper to decrypt a cipher text. The data communication system is constituted by connecting a data transmitting apparatus (13105) to a data receiving apparatus (11201) via a transmission path (110). In the data transmitting apparatus (13105), a multilevel encoding part (111) receives a predetermined first initial value (key information) and information data and generates a multilevel signal that varies in level substantially in a random number manner. A dummy signal superimposing part (118) superimposes a dummy signal on the multilevel signal. A modulating part (112) converts the multilevel signal to a modulated signal of a predetermined modulation form and transmits the modulated signal.

Abstract: An integrated circuit (IC) includes a baseband processing module and a radio frequency (RF) section. The baseband processing module is coupled to convert outbound data or an outbound voice signal into at least one of amplitude modulation information, phase modulation information, and frequency modulation information. The RF section includes an oscillation module, a frequency divider, and power amplifier modules. The oscillation module produces an RF oscillation that it modulates based on the phase or frequency modulation information to produce a modulated RF signal. The frequency divider divides the frequency of the modulated RF signal to produce a frequency divided modulated RF signal. The first power amplifier module amplifies the modulated RF signal in accordance with the amplitude modulation information or a constant to produce a first frequency band outbound RF data or voice signal.

Abstract: Provided is a transmission circuit which is small in size, operates with high efficiency, and outputs a transmission signal having high linearity. A signal generation section 11 generates an amplitude signal m(t) and a phase signal. An angle modulation section 17 angle-modulates the phase signal to output an angle-modulated signal. An amplitude calculation section 12 outputs a discrete value signal V(t) having a plurality of discrete values corresponding to a magnitude of the amplitude signal m(t). A dividing section 13 divides the amplitude signal m(t) by the discrete value signal V(t) to output an amplitude signal M(t). A delta-sigma modulation section 14 delta-sigma modulates the amplitude signal M(t) to output a delta-sigma modulated signal. A variable gain amplifier section 15 amplifies the delta-sigma modulated signal by a gain corresponding to the discrete value signal V(t).

Abstract: RF signal generators (1) are disclosed, having an amplitude-modulated amplifier (80) whose supply voltage (70) is a signal non-linearly filtered (33) dependent on a signal (30) being representative to an envelope signal of a desired output RF signal (81). The non-linear filtering (33) is performed preferably using an envelope-dependent boundary. An input RF signal (65) to the amplifier (80) is amplified using the supply voltage (70) to produce the desired output RF signal (81). The present invention also presents methods for driving such generators (1).

Abstract: An embodiment of the present invention provides an RF log-amp detector, comprising a pre-amplifer at the input of the RF log-amp detector, a plurality of limiters with variable gain connected to the pre-amplifier, wherein the gain of the preamplifier is set to its minimum and the dynamic range is expanded by modifying the amplification gain of the plurality of limiters, thereby increasing the dynamic range and reducing accuracy, after which a coarse measurement of a power level is taken and wherein the RF log-amp detector then defines which pre-amplification level is required based on the course measurement to bring the signal at the output of the preamp within an optimum dynamic range of the log-amp and wherein the pre-amplification gain is then set while the gain of the plurality of limiters are set to their minimum value with the RF log-amp then performing a second measurement with higher accuracy and calculating the final measurement from fine measurements and the pre-amplification gain.

Abstract: The present invention provides methods, apparatus and systems for delivery of digital data to stationary receivers over a terrestrial wireless link at a low data rate using a new coded orthogonal frequency division multiplexing (COFDM) scheme. Digital data is encoded and modulated using coded orthogonal frequency division multiplexing (COFDM) to produce a data stream. The data stream is communicated to a stationary receiver via a terrestrial wireless link having a ratio of (i) 50% coherence bandwidth to (ii) allocated channel bandwidth of not greater than 50%. The COFDM scheme employed by the present invention overcomes the degradation of multipath fading induced by terrestrial channels, such as the Ultra High Frequency (UHF) broadcast channel.

Abstract: A frequency generator (100) takes a signal source (clock or carrier) (101) and generates a edge encoded direct digital modulated differential output signal (110). The differential signal (110) is applied to a frequency extension quadrature generator (FEQG) (112). The FEQG (112) includes a fractional differential wavelength delay locked loop (DLL) (280) and a frequency multiplier (240). The DLL (280) generates a control voltage (214) with which to control delays of the edge encoded modulation signal (110). A frequency extended quadrature function is applied to the periodic steady state input signal with edge encoded modulation (110), to provide the output signal set 113.

Abstract: A digital modulator in a radio transmitter includes circuitry for switching between Gaussian Minimum Shift Keying (GMSK) and Phase-Shift Keying (PSK) while maintaining spectral mask requirements. The digital modulator of the present invention includes both GMSK and PSK symbol mappers that produce PSK in-phase and quadrature symbols and GMSK symbols, respectively, to a pulse shaping block. Based on opposite phases of a modulation control signal, the symbol mappers produce either modulated data or a steam of logic zeros to the pulse shaping block. The pulse shaping block filters the received data and multiplexes the data so that each modulated data stream receives non-zero data during a guard time to avoid abrupt changes in the modulated signal that would violate the spectral mask requirements.

Abstract: A multi-mode modulator includes a first data path to process in-phase signals in a quadrature modulation mode, a second data path to process quadrature signals during the quadrature modulation mode, and a first multiplexer to selectively switch polar amplitude data onto one of the first and second data paths in response to a selection signal.

Abstract: The present invention includes backscatter communication systems, interrogators, methods of communicating in a backscatter system, and backscatter communication methods. According to one aspect of the present invention, a backscatter communication system includes an interrogator including a transmitter configured to output a forward link communication and a receiver configured to receive a return link communication having a carrier signal, the receiver being configured to reduce the amplitude of the carrier signal of the return link communication; and a communication device configured to modulate the carrier signal to communicate the return link communication responsive to reception of the forward link communication.

Abstract: The present invention includes backscatter communication systems, interrogators, methods of communicating in a backscatter system, and backscatter communication methods. According to one aspect of the present invention, a backscatter communication system includes an interrogator including a transmitter configured to output a forward link communication and a receiver configured to receive a return link communication having a carrier signal, the receiver being configured to reduce the amplitude of the carrier signal of the return link communication; and a communication device configured to modulate the carrier signal to communicate the return link communication responsive to reception of the forward link communication.