Abstract: A modulation circuit includes a band restriction filter 2, an attenuator 3, a modulator 4, a reference voltage generator 8, a comparing reference voltage generator 9, a voltage comparator 10 and an attenuator controller 7. The band restriction filter 2 receives modulation data. The attenuator 3 is connected to the band restriction filter 2 for adjusting its attenuation in response to an attenuator control signal. The reference voltage generator 8 is connected to the attenuator 3 for providing a reference voltage independent of a temperature and a power supply voltage to the attenuator. The comparing reference voltage generator 9 is connected to the reference voltage generator 8 for providing a comparing reference voltage independent of the temperature and the power supply voltage. The modulator 4 is connected to the attenuator 3.

Abstract: An inexpensive method and means for generating high power envelope-modulated radio frequency signals is disclosed. Embodiments provide EER amplification and separate modulation of information encoded as phase angle and as amplitude. An envelope modulated signal generation apparatus comprising a source of carrier signal, a source of a binary data stream, a pulse deletion logic and a current switch is disclosed.

Abstract: An ASK modulator which modulates an input signal in accordance with a logic level of the input signal, changes the amplitude of the input signal, and generates an amplitude shift keying (ASK) modulated signal is provided. This ASK modulator has an oscillating means for generating a carrier signal, a frequency filter means which passes a prescribed frequency component of the input signal and outputs a frequency limited signal having the prescribed frequency component, and a modulator which modulates the input signal based on the level of the carrier signal and on the level of the frequency limited signal and outputs the ASK modulated signal having a limited frequency component.

Abstract: An Amplitude Shift Keying (ASK) modulating circuit includes an oscillation circuit generating a pulse oscillation having a given frequency. A frequency divider is provided having a binary counter unit and having at least an input terminal, an output terminal and a reset terminal. The frequency divider is active and inactive when the reset terminal thereof is applied with low and high levels of a transmission signal wave, respectively, and divides the pulse oscillation while the frequency divider is active. The transmission signal wave is modulated together with a carrier frequency which is identical to the divided frequency.

Abstract: The present invention, generally speaking, provides methods and apparatus for producing an amplitude modulated communications signal, in which a constant-envelope carrier signal is modified in response to a power control signal to produce a modified constant-envelope carrier signal. The modified constant-envelope carrier signal is amplified in response to an amplitude modulation signal to produce a communications signal having amplitude modulation and having an average output power proportional to a signal level of the modified constant-envelope carrier signal. This manner of operation allows wide dynamic range of average output power to be achieved. Because amplitude modulation is applied after amplitude varying circuitry used to produce the modified constant-envelope carrier signal, the amplitude modulation is unaffected by possible non-linearities of such circuitry.

Abstract: A transmitting device generates a modulation signal depending on data to be transmitted. The transmitting device includes a transmission frequency generation device that is controlled depending on the signal in order to produce a transmission frequency corresponding to the modulation signal. A calibration device is provided for automatically calibrating the amplitude of the modulation signal during the operation of the transmitting device. This eliminates time-consuming and therefore costly adjustment steps during the production of the transmitting device.

Abstract: This apparatus comprises an amplitude and phase-modulated signal transmitter. This transmitter is formed by a non-linear amplifier (30) for supplying signals based on a portable signal generator (25) to an antenna (10). The apparatus comprises an amplitude modulator (39) which is placed between the amplifier (30) and the antenna (10) and a phase modulator (37) which is placed at the input of the amplifier (30).

Abstract: Systems and methods for enhancing the linearity of a modulator by filtering a set of frequency components from the modulator output to develop a modulator feedback signal. In a preferred embodiment of the invention, a diplexer separates the output of a balanced modulator into a first frequency spectrum and a second frequency spectrum. The first frequency spectrum contains the modulated output signal, and the second frequency spectrum contains the modulator feedback signal which is combined with the modulating signal to enhance the linearity of the modulator.

Abstract: A controlled oscillation modulator includes a comparator and a power amplification stage for pulse modulation, and a higher order oscillating loop comprising first feedback means (21) and first forward means (22) securing stable oscillating conditions. The modulator is characterized by current measurement means, arranged to measure a value (iL) of a current supplied by said power amplification stage to a load (5) connected to the modulator, said measured value being supplied to said first feedback means (21), wherein said first feedback means (21) has a transfer function adapted to generate said first feedback signal based on said measured value (iL), and said first forward means (21) has a transfer function adapted to generate said modulating signal based on said first feedback means and an input signal (Vi). Applications are general DC-DC and DC-AC power conversion with inductive loading. In a preferred embodiment the system implements a precision transconductance amplifier by a current feedback.

Abstract: A power amplifier uses a modulation technique that varies amplitude of a drive signal and, optionally, phase angle of the drive signal. The power amplifier comprises two coupled amplifiers, a first one of which is operated saturated to produce a constant voltage output. The first amplifier is coupled to a second one of the amplifiers via a quarter wave transmission line. The second amplifier is operated in a linear mode to deliver an output signal controlled by an amplitude-modulating signal. The amplitude-modulating signal may be a bipolar modulation signal that produces both positive and negative outputs from the second amplifier that add to or subtract from the output from the first amplifier to develop at a load impedance net output signal amplitudes varying between a minimum or “trough” amplitude and a maximum or “crest” amplitude.

Abstract: Magnetic Vector Steering (MVS) and Half-Cycle Amplitude Modulation (HCAM) are novel techniques which enhance the powering and control of multiple arbitrarily oriented implant devices. Together, these techniques enable arbitrarily oriented implants to receive power and command, programming, and control information in an efficient manner that preserves battery life and transmission time while reducing overall implant device bulk. By steering the aggregate magnetic field from a near-orthogonal set of AC-energized coils, selected implants can be powered or communicated with at desired times. Communication with individual implants can also be enhanced through half-cycle amplitude modulation —a technique that allows bit rates up to twice the energizing frequency. Unlike prior art systems, power and data transfer can be realized over the same frequency channel.

Abstract: An ASK modulator can be operated with only a positive-voltage power source. A source-voltage switching circuit that applies a positive voltage to the source of a FET when a data signal is at an L level in relation to the source of the FET is connected to the source of the FET which has a negative pinch-off voltage. Since the L level of the data signal can be set to 0 V, the ASK modulator can be configured only with the positive-voltage power source. This allows miniaturization and cost reduction to be implemented.

Abstract: Magnetic Vector Steering (MVS) and Half-Cycle Amplitude Modulation (HCAM) are novel techniques which enhance the powering and control of multiple arbitrarily oriented implant devices. Together, these techniques enable arbitrarily oriented implants to receive power and command, programming, and control information in an efficient manner that preserves battery life and transmission time while reducing overall implant device bulk. By steering the aggregate magnetic field from a near-orthogonal set of AC-energized coils, selected implants can be powered or communicated with at desired times. Communication with individual implants can also be enhanced through half-cycle amplitude modulation—a technique that allows bit rates up to twice the energizing frequency. Unlike prior art systems, power and data transfer can be realized over the same frequency channel.

Abstract: A method and a circuit for high-efficiency linear RF-power amplification over a wide range of amplitudes from zero to peak output includes a final RF-power amplifier operating at or near saturation, an RF driver amplifier, a high-level amplitude modulator for the final amplifier, preferably a high-level amplitude modulator for the driver amplifier, and a means for determining the supply-voltage input to the final amplifier and for controlling the amplitude of the drive. The means for determining the supply-voltage input and for controlling the amplitude acts so that the final amplifier drive varies from a minimum level to peak as the desired transmitter output varies from zero to peak. The transmitter is preferably of the envelope-elimination-and-restoration type or the envelope-tracking type.

Abstract: An RF power amplifier system is presented herein. It includes a plurality of RF power amplifier modules. At least two encoders are provided. Each encoder is associated with and controls the operation of some of the plurality of power amplifier modules. Each encoder is associated with different ones of the plurality of amplifier modules. An exciter receives an amplitude varying input signal and periodically provides a command signal to each of the modulation encoders and instructs that modulation encoder as to how many of its associated power amplifier modules are to be turned on as a function of the value of the input signal. Each modulation encoder responds to a received command signal and selects which of its associated power amplifiers to turn on.

Abstract: A communication system that can satisfactorily communicate with a mobile station by a transmitter and receiver of a simple arrangement, wherein a plurality of carriers having different frequencies are transmitted simultaneously and data is transmitted on the basis of a phase difference between the carriers. Also, the carriers are multiplied with a predetermined time waveform and transmitted, so that a reception side receives data by use of a time waveform narrower than the above time waveform.

Abstract: The present invention provides a modulation circuit that has excellent modulation characteristics and can be designed as an MMIC. Consequently, this modulation circuit is such that the modulating wave input means is composed of a capacitor 21 and an inductor 22, the carrier input means is composed of a capacitor 23 and a resistance element 24, the self-bias means is composed of a resistance element 26 and a capacitor 27, the carrier selection means is composed of an inductor 22 and a capacitor 28, and the modulated wave output means is composed of a capacitor 28.

Abstract: A pulse step modulator comprising is disclosed including a plurality of series connected unit step modules, each including a DC voltage source and an associated actuatable switch for, when on, turning on the associated module to provide a unit step voltage. An output circuit is connected to the series connected modules for providing an output voltage to a load wherein the magnitude of the output voltage is equal to the sum of all the voltage sources of the modules that are turned on. A plurality of module turn on signals are provided, each for turning on a switch in one of the modules for the time duration of the turn on signal after which the switch is turned off. Each unit step module includes a transformer means exhibiting an associated unwanted capacitance between transformer means and circuit ground and which capacitance becomes charged when the associated switch is turned on.

Abstract: A digital signal transmission system is provided which minimizes the AM signal envelope distortion caused by multiple digitally modulated carriers in the same band as the AM signal. The system transmits an amplitude modulated signal. Digital carriers for the digital signal are placed both above and below the frequency of the analog AM carrier. Certain digital carriers that are above the frequency of the analog AM carrier have an associated digital carrier that is at an equal frequency offset below the analog AM carrier. The data and modulation placed on the upper digital carrier and its counterpart are such that the signal resulting from their addition has no component that is in-phase with the analog AM carrier. The signal envelope is predistorted to counteract the distortion added by the digital carriers.

Abstract: A band limited Amplitude Shift Keyed (ASK) modulator employing linear modulation and an efficient Class C power amplifier. Band-limited operation is provided by filtering a digital baseband input signal prior to modulation. Closed loop feedback is employed around the amplifier to assure linear modulation over a wide modulation range which preserves the frequency characteristics of the baseband signal on the modulation envelope. Further filtering is accomplished by exploiting the closed loop system response, incorporating it in the filter characteristic as an added filter pole.

Abstract: Methods and apparatus for converting a relatively low frequency signal, e.g., a 1.5 MHz signal, to a high frequency signal, e.g., a 30-100 MHz signal, in the digital domain. An interpolation technique is used to convert the low rate digital signal to a high rate signal and to shift the carrier to a desired frequency. This is accomplished, by first positioning the information signal, e.g., the digital wave form to be modulated on a carrier at a relatively low rate using a digital mixer operating at a fraction of the ultimate digital to analog conversion frequency. The relatively low rate signal generated by the mixing operation is then converted to a high rate signal by one or more interpolation stages. An adjustable passband filter circuit is included in each interpolation stage for selectively filtering out the signal or images created as a result of a signal padding operation performed as part of each interpolation stage.

Abstract: In an amplitude modulator, a delta sigma modulator converts a digital or analog modulation signal into a binary signal. The binary signal and a carrier signal are sent to a multiplication circuit. The phase of the carrier signal is changed to normal phase or opposite phase. The resultant carrier signal is output as an amplitude modulation wave. An orthogonal modulator sends a local oscillation signal to a phase shifter. The phase shifter outputs two carrier signals with phases which differ by 90.degree. each other. The modulation signal and carrier signals are sent to the amplitude modulator. The amplitude modulator outputs an amplitude modulation signal. These signals are sent to an analog signal composing unit. The analog signal composing unit composes the input signals and outputs an amplitude and phase modulation signal.

Abstract: A method for amplitude modulating signals, and a circuit that operates in accordance with the method. The method includes a first step of applying a modulating low frequency signal having a time-varying voltage to a tunable resonator. The tunable resonator exhibits parallel and series resonances at frequencies which shift as a function of the time-varying voltage. A second step includes applying an RF carrier signal having a frequency that is between the parallel resonant frequency and the series resonant frequency to the tunable resonator. In response thereto, the tunable resonator causes the RF carrier signal to be attenuated as a function of the time-varying voltage of the modulating low frequency signal. Also provided is a method for phase modulating signals, and a circuit that operates in accordance therewith. A first step includes applying a modulating low frequency signal having a time-varying voltage to a tunable resonator.

Abstract: A high frequency arbitrarily modulated signal and noise generator utilizes digital numerically controlled oscillators providing interbusiness directly to an adder and which are phase modulated. The digital adder feeds a digital analog converter, eliminating the need for a digital multiplier while providing amplitude or phase modulation with high resolution and at high processing speeds.

Abstract: An amplitude control system uses a pair of parallel integrators to rapidly adjust the amplitude of a test signal between two precisely determined power levels in an RF signal generator. The amplitude control system initializes a first power level by switching a first integrator into a feedback signal path to establish a first drive voltage, corresponding to the first power level. A second power level is initialized by switching a second integrator into the feedback signal path to establish a second drive voltage, corresponding to the second power level. The amplitude control system then alternately switches each of the integrators into the feedback signal path to alternately apply the first and second drive voltages to a level modulator, which rapidly adjusts the amplitude of the test signal to each of the two initialized power levels.

Abstract: An amplitude modulation circuit and method. A predetermined number of (e.g., 6) drivers and differentially switched power amplifiers are provided in pairs. A program sound signal which has been quantized into a predetermined number of bits (e.g., 12 bits) is divided through a ROM into a plurality of bit groups each consisting of a predetermined number of bits (e.g., 2 bits), which are in turn distributed to the respective driver and differentially switched power amplifier pairs. In response to the value of the distributed bit group, each driver selects two different phase-shift carriers from seven different phase-shift carriers, and provides as its outputs .phi..sub.A and .phi..sub.B. With the output phase-shift carriers (.phi..sub.A and .phi..sub.B), each driver differentially switches the differentially switched power amplifier corresponding thereto. The output of each differentially switched power amplifier is weighted.

Abstract: A digitized quadrature modulator receives an I-channel input digital signal and Q-channel input digital signal, and quadrature modulater the I-channel and Q-channel input digital signals by digital signal processing. The modulator has a digital filter (504) for shaping the spectrum of the I-channel and Q-channel input digital signals to provide I-channel and Q-channel output signals. The output signals have a predetermined phase shift between the I-channel and the Q-channel so as to compensate a phase difference based upon the quadrature modulation by the digital signal processing. Complementers (505a, 505b) for taking the complement of the I-channel and Q-channel output signals to provide I-channel and Q-channel complement signals. A multiplexer (505c) multiplexer the I-channel and Q-channel output signals from the digital filter and the I-channel and Q-channel complement signals from the complementers to provide a quadrature modulated output signal.

Abstract: In an amplitude modulator, a delta sigma modulator converts a digital or analog modulation signal into a binary signal. The binary signal and a carrier signal are sent to a multiplication circuit. The phase of the carrier signal is changed to normal phase or opposite phase. The resultant carrier signal is output as an amplitude modulation wave. An orthogonal modulator sends a local oscillation signal to a phase shifter. The phase shifter outputs two carrier signals with phases which differ by 90.degree. each other. The modulation signal and carrier signals are sent to the amplitude modulator. The amplitude modulator outputs an amplitude modulation signal. These signals are sent to an analog signal composing unit. The analog signal composing unit composes the input signals and outputs an amplitude and phase modulation signal.

Abstract: The present invention provides a system and method in which an arbitrary information-modulated signal is efficiently amplified to high power levels. The arbitrary information-modulated signal is received at a low power level and is separated into elemental signals. In a preferred embodiment, a frequency/phase information signal and an amplitude information signal are the elemental signals which collectively represent the essential information in the original information-modulated signal. The circuit uses the elemental signals to provide an amplified replica of the original information-modulated signal. The amplification preferably, though not necessarily, involves using the digital amplitude modulators disclosed in U.S. Pat. No. 4,804,931, U.S. Pat. No. 5,260,674, or U.S. Pat. No. 5,367,272.

Abstract: A multi-level superposed amplitude-modulated baseband signal processor which has simple hardware structure and a filtering effect for bandwidth and power efficiency in a digital transmission system includes a data delayer, a signal level converter, an operator, two pulse generators, two adders and two amplifiers, thereby eliminating the need for conventionally required pulse waveforms and simplifying circuit structure. Specifically, when the number of the multi-levels is desired to be changed, the relevant multi-level superposed amplitude-modulated baseband signal can be provided by a simple change of the processor.

Abstract: A digital AM transmitter according to the invention converts a audio signal to a digital audio signal of a plurality of bits by an A/D converter, outputs a logical code signal of "1" from each of those output terminals of a code unit, whose number corresponds to the digital value of the digital audio signal, selectively generates driving signals from those output terminals of a code shifter which are equal in number to the logical code signals of "1" from the code unit, while changing the driving-signal-generating output terminals of the code shifter from one to another (or some to others) with the lapse of time, selectively guiding, with the use of carrier wave switches, those portions of a carrier wave signal which have been divided by a carrier wave divider, to power amplifiers in accordance with driving signals generated from the code shifter, amplifies the guided portions of the carrier wave signal by power amplifiers, combined the amplified portions of the carrier wave signal by a combiner, and passes t

Abstract: A method for simultaneously imposing a single modulating signal on a number of constant frequency carriers includes applying the single modulating signal and all of the carriers to a doubly-balanced mixer circuit that produces sideband signals that are uncontaminated by the carriers. The sideband signals thus produced are then combined with signals proportional to the carriers in a linear circuit to obtain an output signal equivalent to a signal that would result from combining separately modulated carriers.

Abstract: The process according to the invention consists in breaking down a radiofrequency signal to be modulated according to a first and second signal, representing respectively the sum of the output voltages of identical amplitude of a first and second determined number of modules, with which respectively a first and second vector are associated whose respective amplitude and phase verify that the vectorial sum of the two vectors coincides with a determined reference that is used as a phase reference of the two vectors, in adapting the phase of the load impedance of each module so that vector associated with the current supplied by each of the amplifying modules is in phase delay in relation to their output voltages, in modulating the phase of the two signals by the modulation signal and in adding the first and second phase modulated signal to obtain a resultant amplitude modulated signal. Application: Medium wave radio broadcast transmitters.

Abstract: A pulse step modulator includes a plurality of N series connected unit step modules each including a DC voltage source having a value V. A plurality of M series connected binary step modules are connected together in series with the series connected unit step modules with each binary step module including a DC voltage source having a value which is a fraction of V. Each module has an associated actuatable switch means for, when actuated, turning on the associated module to provide a step voltage. An output circuit connected to the series connected modules for providing an output voltage to a load wherein the magnitude of the output voltage is equal to the sum of all of the voltage sources of the modules that are turned on. An analog input signal is converted into digital words, each word including first and second multi-bit digital portions.

Abstract: A first aspect of the present modulator provides for a reduction in an otherwise maximum level of an analog input signal during a particular time period (for example, the period of the synchronization pulse in an analog television format). When the normally predictable high-amplitude portion is reduced in amplitude, combiner power efficiency is increased. To regain the full amplitude, the gain of the amplifier corresponding to the most significant bit of the digitized signal being modulated, is increased. A second aspect of the present modulator provides an automatic gain control AGC arrangement especially suitable for the modulator of U.S. Pat. No. 4,804,931. The AGC arrangement is based on a circuit that is governed by the output of a respective amplifier as well as by the binary value of the respective bit corresponding to the significance of the amplifier and a reference value related to the bit's significance.

Abstract: A noise adaptive automatic gain control circuit (100) includes an automatic gain control amplifier (105) for automatically adjusting the gain of the circuit (100) in response to an input signal applied to the input. A detector (135) is provided for detecting the presence of any background noise that may be present. Further, a voltage generator (126), a comparator (124), and a microcomputer (150) is provided for dynamically adjusting the gain of the AGC amplifier (105) to substantially prevent the amplification of the background noise. In other aspects of the present invention, a voice lull detector (140) detects voice lulls (402) in the input signal applied to the input. Further, a programmable amplifier (120) substantially maintains the gain of the AGC amplifier (105) to a constant level during voice lulls (402) to prevent excessive amplification.

Abstract: Disclosed herein is a synchronous single cycle sample and control amplitude modulator for use with any carrier frequency. The modulator includes both a data input and a sine wave generator coupled with a sample and hold device. The sample and hold device synchronizes the data and the sine wave signal and then transmits the synchronized signal to a modulator. The modulator modulates the synchronized data and the sine wave signal such that a sampled and controlled, synchronous single cycle amplitude modulated signal is produced.

Abstract: A constant-amplitude wave combination type amplifier includes a first amplifier outputting a first amplified output, and a second amplifier outputting a second amplified output. The constant-amplitude wave combination type amplifier also includes a first constant-amplitude wave generating circuit for combining an input wave and the second amplified output from the second amplifier and for generating a first constant-amplitude wave which is input to the first amplifier, and a second constant-amplitude wave generating circuit for combining the input wave and the first amplified output from the first amplifier and for generating a second constant-amplitude wave. Further, the constant-amplitude wave combination type amplifier includes a wave combining circuit for combining the first and second constant-amplitude waves and for generating an output wave.

Abstract: Neutrinos and antineutrinos are generated by electromagnetic excitation of elementary subatomic particle magnetic moments in a DC magnetic field and causing the orientation energy of magnetic moments resulting from such excitation to be converted into the neutrinos and/or antineutrinos. A beam of neutrinos and antineutrinos is derived by enclosing a neutrino antineutrino source with neutrino scattering crystals having an aperture therein. Neutrinos and/or antineutrinos are amplitude modulated by varying the amplitude of electromagnetic excitation of the elementary particle magnetic moments, or the DC field or momentum mechanically imparted to a stiff crystal including the subatomic particles.

Abstract: A first aspect of the present modulator provides for a reduction in an otherwise maximum level of an analog input signal during a particular time period (for example, the period of the synchronization pulse in an analog television format). When the normally predictable high-amplitude portion is reduced in amplitude, combiner power efficiency is increased. To regain the full amplitude, the gain of the amplifier corresponding to the most significant bit of the digitized signal being modulated, is increased. A second aspect of the present modulator provides an automatic gain control AGC arrangement especially suitable for the modulator of U.S. Pat. No. 4,804,931. The AGC arrangement is based on a circuit that is governed by the output of a respective amplifier as well as by the binary value of the respective bit corresponding to the significance of the amplifier and a reference value related to the bit's significance.

Abstract: A digital quadrature modulator having a first storage device for receiving an I phase component of a digital baseband signal and digital carrier phase information as a higher order address and a lower order address, respectively, and a second storage device for receiving a Q phase component of the digital baseband signal and the digital carrier phase information as a higher order address and a lower order address, respectively. The carrier phases of the carrier phase information applied to the first and the second storage devices are out of phase from each other by .pi./2. The first storage device outputs a multiplication result of the I phase component and a carrier signal and the second storage device outputs a multiplication result of the Q phase component and the carrier signal based on these addresses. These outputs are added to each other in a digital manner and then converted into an analog signal which is supplied as a modulated signal.

Abstract: Circuitry for reducing harmonic distortion in an amplifier includes a first transistor having a first non-linear collector-to-substrate capacitance, a first load device coupled to a collector of the first transistor, a first current source coupled to an emitter of the first transistor, a first conductor conducting an input voltage coupled to a base of the first transistor, and a second conductor coupled to the first load device and conducting an output voltage of the amplifier. The first transistor produces a first non-linear current in the first non-linear collector-to-substrate capacitance in response to the input voltage. A second transistor has a second non-linear collector-to-substrate capacitance. A second current source is coupled to an emitter of the second transistor. The first conductor is coupled to apply the input voltage to a base of the second transistor.

Abstract: Arrangements are provided for generation of dual-tone waveforms utilizing direct digital waveform synthesis techniques and architecture and retaining the advantageous characteristics of direct digital waveform synthesis. Preferred embodiments feature combination of generated waveforms at an analog adder, a digital adder using a single digital-to-analog converter and at a single wave table, respectively, each providing particular hardware economies and operational advantages with respect to other preferred embodiments.

Abstract: This invention discloses a signal processing apparatus which has N nonlinear oscillators, a circuit for coupling the N nonlinear oscillators in a loop-like form, a circuit for shifting the phase of the output signal of a particular nonlinear oscillator from among the N nonlinear oscillators in correspondence with an input signal, and a circuit for outputting the output of at least one oscillator of the N nonlinear oscillators as the output of the signal processing apparatus. This apparatus has capability to effect analog conversion, modulation or storage of an input signal.

Abstract: An amplitude modulation apparatus for achieving an extremely deep extinction ratio (in excess of -90 dBc) at nanosecond rise times required by an SAW device comprises the cascaded combination of a controlled switching device (GaAsFET), capable of providing a medium degree (40 dB) of attenuation at nanosecond switching rates, and a double balanced mixer, both multiplier input ports of which are coupled to receive split outputs from the GaAsFET switch. Because of the nonlinearity of the transfer function of the mixer when driven by the same RF carrier input at both multiplier ports, the output of the mixer is in excess of -90 dBc. In an SAW-based signal processing system, the output of the mixer is coupled to RF drive input of the SAW device.

Abstract: A binary signal modulator includes a sampling circuit for sampling a binary signal at a predetermined sampling frequency, a modulating circuit responsive to the sampled binary signal for generating a modulating signal, the rising and decaying timings of which are respectively determined by the start and end times of the binary signal and the rising and decaying characteristics of which are respectively defined as predetermined functions, and a circuit responsive to the modulating signal for generating a modulated signal.