Abstract: Circuitry for ultrasound devices is described. A multilevel pulser is described, which can provide bipolar pulses of multiple levels. The multilevel pulser includes a pulsing circuit and pulser and feedback circuit. Symmetric switches are also described. The symmetric switches can be positioned as inputs to ultrasound receiving circuitry to block signals from the receiving circuitry.

Abstract: A synthesizer comprises a two-point modulation phase locked tow, TPM PLL, circuit configured to receive a frequency tuning signal and to generate a stepped chirp signal in an intermediate frequency range by applying a two-point modulation PLL on the frequency tuning signal, and a subsampling PLL circuit configured to receive the stepped chirp signal in a mm-wave frequency range and to generate a smoothened chirp signal in a mm-wave frequency range by applying a subsampling PLL on the stepped chirp signal.

Abstract: An active ring mixer circuit for use in a receive or transmit channel of an RF radio. The circuit comprises plural transistor pairs arranged in a ring and biased into an active or saturation region. A first input is adapted to receive an RF signal. The first input is electrically combined with the plural transistor pairs to provide negative feedback to the plural transistor pairs. A second input electrically combined with the plural transistor pairs is adapted to receive a local oscillator signal. An output of the mixer is adapted to provide a mixed signal from the plural transistor pairs. Advantageously, the mixer circuit induces little low frequency spurs that may interfere with radio operation and has significantly reduced power consumption, lower noise figure, and good balance.

Abstract: A method for processing an audio signal (i(t)), comprises: receiving a first set (x(t)) of time-varying signals representing a first sound comprised in the audio signal (i(t)), the first set (x(t)) of time-varying signals comprising an amplitude modulation signal (a(t)), a carrier frequency signal (fc(t)), a pitch signal (f0(t)) and an FM index signal (h(t)); and modifying the first set (x(t)) of time-varying signals by modifying the amplitude of the FM index signal (h(t)), thereby providing a first modified set (x?(t)) of time-varying signals. The resulting first modified set (x?(t)) of time-varying signals may subsequently be modulated to provide an audio output signal.

Abstract: An apparatus for coding a signal by means of amplitude shift keying comprises a class E amplifier including a switching transistor, to whose gate is supplied a voltage having an operating frequency for operating the class E amplifier. For achieving an amplitude shift keying in the output signal of the class E amplifier, a circuit for switching the operating frequency of the voltage supplied to the gate of the switching transistor, or the resonance frequency of the class E amplifier, between a first value and a second value is provided and in order to switch a deviation degree between the operating frequency and the resonance frequency between a first value and a second value.

Abstract: A phase-locked loop double-point modulator may include a frequency divider having a ratio which can be changed by a first modulation signal, and an oscillator, a frequency of which can be changed by a second modulation signal correlated to the first modulation signal. A calibration circuit may be configured, in a calibration mode, to match the gains of the first and second modulation signals based on frequency measurements of the oscillator for two different calibration values of the second modulation signal. The phase-locked double-point modulator may also include an attenuator having a constant ratio greater than 1 and placed in the path of the second modulation signal, and a selector switch configured to be controlled by the calibration circuit to reduce the ratio of the attenuator in the calibration mode.

Abstract: The present invention relates to a method of transmitting and a method of receiving signals and corresponding apparatus. One aspect of the present invention relates to an efficient L1 signaling method for an efficient transmitter and an efficient receiver using the efficient L1 signaling method for an efficient cable broadcasting.

Abstract: A quadrature out-phasing system comprising: a first baseband signal modifier (6) arranged to receive a first baseband signal component (2) and output a first constant envelope RF carrier (12) and a second constant envelope RF carrier (14); and a second baseband signal modifier (8) arranged to receive a second baseband signal component (4) and output a third constant envelope RF carrier (16) and a fourth constant envelope RF carrier (18). The system may further comprise: a first signal combiner (500) arranged to combine the first constant envelope RF carrier (12) and the second constant envelope RF carrier (14), and arranged to output a first RF PWM signal (94); and a second signal combiner (502) arranged to combine the third constant envelope RF carrier (16) and the fourth constant envelope RF carrier (18), and arranged to output a second RF PWM signal (96).

Abstract: Enhanced polar modulator for transmitter. Within a phase locked loop (PLL), two point modulation topology is employed in which phase information passes through a limiter (e.g., a ±90° or ±?/2), the phase information dynamic range is divided by a factor (e.g., by 2), and a maximum frequency deviation is also divided by a factor (e.g., by 2). Then, a double balanced up-converter mixer/modulator performs gain adjustment (e.g., magnitude and/or amplitude adjustment) and phase changes of 0° and +180° or 0 and +? (e.g., negative gains values may be employed). Phase adjustment in such an architecture is split and provided to both the PLL and to the mixer/modulator of such a polar modulator within a transmitter module such as may be implemented within a communication device (e.g., which may be a wireless communication device). This architecture that includes a PLL with a double balanced up-converter mixer/modulator suppresses even harmonics.

Abstract: A fan speed control circuit includes a first fan, a second fan, a first temperature sensor, a second temperature sensor, a PWM regulator, and a driving module. The first temperature sensor senses a temperature of the first component to generate a first temperature signal. The second temperature sensor senses a temperature of a second component to generate a second temperature signal. The PWM regulator is connected to the first temperature sensor and the second temperature sensor. The PWM regulator generates a first PWM signal according to the first temperature signal and generates a second PWM signal according to the second temperature signal. The driving module is connected to the PWM regulator. The driving module generates a first driving voltage provided to the first fan according to the first PWM signal. The driving module also generates a second driving voltage provided to the second fan according to the second PWM signal.

Abstract: In order to generate a broadband, frequency-modulated output signal, of which the carrier frequency is adjustable within a wide frequency range, a frequency-modulated signal is generated on an arbitrary, fixed carrier frequency, which is then converted into IQ signals, and the IQ signals generated in this manner are combined with the desired carrier frequency by IQ modulation to form the frequency-modulated output signal. By preference, the generated IQ signals are low-pass filtered before the IQ modulation.

Abstract: A method and device for the simultaneous compensation of several signal errors that occur in an IQ-modulator, using respective inverse correction signals, wherein the optimized signal magnitude of each correction signal is calculated by the determination of the effective signal error and by the subsequent iterative minimization of the effective signal error.

Abstract: Apparatus and methods for improving the spectral performance of a polar modulator are described. A composite FM signal component of a composite polar transmit signal may be processed by monitoring the FM signal to detect a transient burst component, and, responsive to detection of a transient burst, generating a spectrally friendly replacement signal component that may be combined with the FM signal to improve spectral performance of the composite signal. In addition, an associated AM component of the composite transmit signal may be filtered to further improve spectral performance.

Abstract: Enhanced polar modulator for transmitter. Within a phase locked loop (PLL), a two point modulation topology is employed in which phase information passes through a limiter (e.g., a ±90° or ±?/2) in which the phase information dynamic range is divide by a factor (e.g., by 2) and a maximum frequency deviation is also divided by a factor (e.g., by 2). Then, a double balanced up-converter mixer/modulator is implemented to perform gain adjustment (e.g., magnitude and/or amplitude adjustment) and phase changes of 0° and +180° or 0 and +? (e.g., negative gains values may be employed). Phase adjustment in such an architecture is split and provided to both the PLL and to the mixer/modulator of such a polar modulator within a transmitter module such as may be implemented within a communication device (e.g., which may be a wireless communication device). This architecture that includes a PLL with a double balanced up-converter mixer/modulator suppresses even harmonics.

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: Various apparatuses and methods for offsetting the phase and/or frequency of a clock signal are disclosed herein. For example, some embodiments provide an apparatus for generating a clock signal, including a quadrature delay circuit connected to an input clock signal. The quadrature delay circuit outputs components of the input clock signal with different phase shifts. A first amplitude modulator is connected to the first output of the quadrature delay circuit, and a second amplitude modulator is connected to the second output of the quadrature delay circuit. A summer combines the output of the first and second amplitude modulators.

Abstract: The present disclosure relates to I/Q modulation circuits, devices, and methods.

Abstract: Provided are apparatuses and methods for digital FM modulation. In one example, a message signal is integrated by an integrator to transform the message signal into a complex signal. The complex signal may include at least two complex components that may interfere to produce an FM modulated carrier signal. Hence, in this example, the method and apparatus for digital FM modulation may produce an FM modulated carrier signal without phase shifting. In another example, a lookup table is not necessary for modulation of the carrier signal.

Abstract: A polar transmitter includes a two-point modulation phase-locked loop (PLL) for producing an RF signal with a wide bandwidth. The PLL includes a first input for receiving a phase signal of a variable-envelope modulated signal and providing the phase signal along a first signal path to produce a first frequency modulation signal and a second input for receiving the phase signal and providing the phase signal along a second signal path to produce a second frequency modulation signal. The PLL further includes a voltage controlled oscillator (VCO) having two modulation points, one for receiving the first frequency modulation signal and the other for receiving the second frequency modulation signal. The VCO is controlled by an aggregate of the first frequency modulation signal and the second frequency modulation signal to up-convert the phase signal from an IF to an RF to produce the RF signal with a wide bandwidth.

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: There are included a first quadrature modulation part (5) that divides an input signal into an I signal and a Q signal having a phase orthogonal to the phase thereof and uses a baseband frequency to perform frequency conversions of the I and Q signals, thereby performing a quadrature modulation; and a second quadrature modulation part (8) that uses in-phase and quadrature carriers of FM frequencies, which are 90 degrees out of phase with respect to each other, to perform frequency conversions of the I and Q signals, which are generated by the first quadrature modulation part (5), thereby performing a quadrature modulation.

Abstract: Random number generators are used for entertainment in gambling, lotteries and video gaming devices. True Random Number Generators, as are now currently defined, must be actuated by a physical noise source, typically based on the uncertainty of the phase differences of a stable and an unstable autonomous oscillator. In this invention an autonomous random frequency modulated oscillator driven by a self contained pseudo-random number generator outputs three loosely correlated random binary streams. Included in the invention is a hardware method for proving wandering phase differences and also the existence of a colored random distribution of concatenated nibbles.

Abstract: In order to generate a broadband, frequency-modulated output signal, of which the carrier frequency is adjustable within a wide frequency range, a frequency-modulated signal is generated on an arbitrary, fixed carrier frequency, which is then converted into IQ signals, and the IQ signals generated in this manner are combined with the desired carrier frequency by IQ modulation to form the frequency-modulated output signal. By preference, the generated IQ signals are low-pass filtered before the IQ modulation.

Abstract: Enhanced polar modulator for transmitter. Within a phase locked loop (PLL), a two point modulation topology is employed in which phase information passes through a limiter (e.g., a +90° or +re/2) in which the phase information dynamic range is divide by a factor (e.g., by 2) and a maximum frequency deviation is also divided by a factor (e.g., by 2). Then, a double balanced up-converter mixer/modulator is implemented to perform gain adjustment (e.g., magnitude and/or amplitude adjustment) and phase changes of 0° and +180° or 0 and +re (e.g., negative gains values may be employed). Phase adjustment in such an architecture is split and provided to both the PLL and to the mixer/modulator of such a polar modulator within a transmitter module such as may be implemented within a communication device (e.g., which may be a wireless communication device). This architecture that includes a PLL with a double balanced up-converter mixer/modulator suppresses even harmonics.

Abstract: A quadrature modulation circuit includes a mixer circuit including an integrated sign modulation control circuit and a plurality of mixer ports. The mixer ports include a first input port, a second input port, an output port and a sign modulation control port. The modulation circuit generates a modulated signal by operation of the mixer circuit multiplying a modulating signal applied to the first input port with a carrier signal applied to the second input port to generate a mixed signal output from the output port, and by operation of the integrated sign modulation control circuit controlling polarity switching of a signal at one of the mixer ports in response to a sign modulation control signal input to the sign modulation control port.

Abstract: Methods, computer-readable medium, a transmitter, a receiver and a transceiver include the transmitter and the receiver in a digital communication system for reducing the transmit power level when there is no user data is to send, i.e., when dummy data is sent instead. That is achieved by defining a symbol alphabet Q and scrambling a modulated bit stream including user data and dummy data with randomly generated symbols from the symbol alphabet Q.

Abstract: A polar transmitter includes a two-point modulation phase-locked loop (PLL) for producing an RF signal with a wide bandwidth. The PLL includes a first input for receiving a phase signal of a variable-envelope modulated signal and providing the phase signal along a first signal path to produce a first frequency modulation signal and a second input for receiving the phase signal and providing the phase signal along a second signal path to produce a second frequency modulation signal. The PLL further includes a voltage controlled oscillator (VCO) having two modulation points, one for receiving the first frequency modulation signal and the other for receiving the second frequency modulation signal. The VCO is controlled by an aggregate of the first frequency modulation signal and the second frequency modulation signal to up-convert the phase signal from an IF to an RF to produce the RF signal with a wide bandwidth.

Abstract: An RF transmitter includes a modulating circuit adapted to modulating an RF signal, an output amplifier adapted to amplify the modulated RF signal; an auto tuner generating a tuning voltage that varies in accordance with operating temperature fluctuations and/or manufacturing process variances, and a reference current generating circuit adapted to generate a reference current in response to the tuning voltage.

Abstract: To modulate the frequency of a signal to be transmitted, the biasing voltage applied to a terminal of a transistor is dynamically modulated. To achieve this, the pulse width or a pulse amplitude of a control signal is modulated. Alternatively, a multi-bit control signal may be used to perform the modulation. The frequency of the transmitted signal is optionally modulated by varying the temperature of a oscillator. To vary this temperature, the current flowing through one or more resistive elements positioned in proximity of the oscillator is varied in response to the pulse width or amplitude of a second control signal. The temperature may also be changed by varying a multi-bit control signal. As the level of this current flow varies, the amount of heat emitted by the resistors vary, thereby changing the temperature of the oscillator which has a non-zero temperature coefficient.

Abstract: A dual mode power amplifier can include a linear gain section and a non-linear gain section configured together as a polar amplifier. The dual mode power amplifier may be used to transmit GFSK, 4-DPSK, and 8-DPSK modulated data. In one mode, both non-linear and linear gain sections may be used to transmit 4-DPSK and 8-DPSK modulated data. Alternatively, in another mode, the linear gain section may be bypassed while the non-linear gain section may be used to transmit GFSK modulated data. By selecting the operating mode, the dual mode power amplifier may be advantageously configured to use relatively less power while supporting GFSK, 4-DPSK, and 8-DPSK modulation schemes.

Abstract: First and second calibration signals (308, 309) are sent to a frequency divider (102) and an adder (116) of a PLL section (100A), demodulated in a demodulator (111), filtered through a low pass filter (113) and a high pass filter (114) and thereafter sent to a modulation signal control circuit (115). The modulation signal control circuit (115) generates control information (318) in comparison with the phase and amplitude of the first and second calibration signals (308 and 309) and sends the control information (318) to a modulation control signal generator (106). Modulation control signal generator (106) holds the control information (318) and controls the values of the first modulation signal and second modulation signal sent to the frequency divider (102) and adder (116) on the based on the control information (318) held in modulation operation.

Abstract: Disclosed is method of controlling an asymmetric waveform generator including the steps of providing a reference timer signal, and generating an asymmetric waveform as a combination of a first sinusoidal wave having a first frequency and a second sinusoidal wave having a second frequency approximately twice the first frequency. The generated asymmetric waveform is sampled to obtain a set of data points, which set of data points is indicative of the generated asymmetric waveform. The method includes analyzing the set of data points in terms of at least a first function relating to an ideal sinusoidal wave of the first frequency, to determine a first set of resultant values relating to the first sinusoidal wave, and analyzing the set of data points in terms of at least a second function relating to an ideal sinusoidal wave of the second frequency, to determine a second set of resultant values relating to the second sinusoidal wave.

Abstract: The operating method is based on the simultaneous application of FM and AM, and is distinguished by passing through three operating states, specifically a warm-up phase, an impressing phase and the continuous operation. In the warm-up phase, the f002_hor is selected as fundamental frequency of the AM, or an AM is dispensed with. The impressing phase is distinguished by a temporally changing AM deviating from the conditions of the continuous operation and having an AM degree different from zero. In the continuous operation, constant conditions of the AM in the case of which the f002_hor is reached as fundamental frequency of the AM, and the AM degree is at 20 to 25% are characteristic.

Abstract: A transceiver and transmitter are shown. A baseband processor receives a signal for transmission. It converts the signal into amplitude and phase polar components. Each component is then processed—the phase component through a wideband phase modulator and the amplitude component through a wideband amplitude modulator, and the components are then recombined for further processing or transmission.

Abstract: An input circuit for an HF-transmitting component 1 of a battery-operated device for the transmission of a data signal aims to reduce the power consumption. For that purpose the fundamental frequency of a reference oscillator 5 is modulated with the digital data signal, the data rate being greater than 20 kchip/s. For smoothing of the modulated reference signal an amplitude limiter 11 and a band pass filter 15 are connected between the reference oscillator 5 and the HF-transmitting component 1.

Abstract: A multi-protocol modulator capable of supporting two or more different modes of operation, each mode of operation corresponding to a different type of modulation, comprises an m-level phase shift keying (m-PSK) modulator which receives a serial input data stream and maps data contained therein into a constellation including m equidistant phases in accordance with a predetermined mapping scheme. The m-PSK modulator is shared by at least two different modulation protocols by allowing the mapping scheme to be selectively changed depending upon the modulation protocol used. The multi-protocol modulator further includes a phase rotator operatively coupled to the output of the m-PSK modulator. The phase rotator selectively rotates the phase of the m-PSK signal by a predetermined phase rotation value. The phase rotator is shared by the two or more modulation protocols by allowing the phase rotation value to be selectively modified depending upon the modulation protocol used.

Abstract: A modulator and a method of modulating utilizes phase or frequency modulation and amplitude modulation. A delay circuit or synchronization circuit is utilized to coordinate the performance of amplitude modulation and phase modulation. The amplitude modulation can be provided after phase modulation is provided to the signal. The modulation circuit can be utilized in any frequency range including high frequency and low frequency circuits.

Abstract: In a digital wireless audio transmission system, a transmitter section includes a local oscillator and frequency modulator to modulate the local oscillator signal with a periodic transmitter spreading signal in order to generate a frequency-modulated radio-frequency signal. An amplitude modulator amplitude-modulates this signal with serial digital data that is generated by an audio interface and a channel encoder. This amplitude-keyed signal which is spread in frequency is then transmitted via a transmit antenna as electromagnetic waves. A receiver section receives these electromagnetic waves via multiple antennae and amplitude-modulates the signal of at least one antenna with antenna modulator signals that have the same frequency as the transmitter spreading signal and a fixed relative phase deviation. All of these antenna signals are then added, and the sum signal is amplified and detected by a small-signal detector.

Abstract: A transmitter and a phase locked loop (30) for a transmitter are disclosed. The phase locked loop (30) upconverts the frequency of a baseband signal to a frequency for radio transmission. As well as the usual components, the phase locked loop (30) comprises a modulator (39) for modulating a baseband signal (f.sub.bb) onto a carrier (f.sub.ref /R) and forwarding the resultant modulated signal (f.sub.c) to one of the inputs of the phase detector (33). It also comprises a low pass filter (38) in its forward path between the phase detector (33) and the voltage controlled oscillator (34) for passing signals having baseband signal frequencies. A mixer (35) and main frequency divider (36) are provided in the feedback path to downconvert the transmit signal (f.sub.tx). This low division eliminates large amounts of multiplicative noise within the loop bandwidth, and therefore enables a large loop bandwidth to be used. Consequently, the settling time of the phase locked loop is improved.

Abstract: In a single-chip multistandard video modulator arrangement in which audio signals for transmission with video signals are first modulated onto a subcarrier and then combined with the video signals for modulation onto a VHF or UHF main carrier, the modulated subcarrier signals are passed through a high-pass filter before being combined with the video signals in order to reduce the amplitude of any audio frequency components, and the resulting variations in main carrier amplitude, which tend to produce "sound in vision" effects.

Abstract: A system and method is disclosed that provides a means for the high efficiency low distortion amplification of complex modulated radio frequency signals, such as but not limited to Single Side Band (SSB) signals. The innovative principle of the invention is based on the simultaneous amplitude and phase or angle modulation of Class "C" amplifier. Complex signals such as SSB signals can be described as a combination of amplitude and phase or angle modulation. By determining the amplitude and phase or angle components of the complex signal and using these to modulate a Class "C" amplifier, according to the manner prescribed in the invention, the objective of high efficiency low distortion is achieved. Previously, Class "B" amplifiers were required to amplify complex RF signals. The maximum efficiency of a Class "B" amplifier typically achieved in practice is about 40 percent compared to about 85 percent for Class "C" amplifiers.

Abstract: A multiple-modulation communication system includes a transmitter that modulates and transmits communication signals modulated by a first modulation technique and communication signals modulated by a second modulation technique. The first modulation technique and the second modulation technique are different. The communication system also includes a receiver capable of receiving the communication signals modulated by the first modulation technique and the communication signals modulated by the second modulation technique and demodulating the communication signals.

Abstract: A system (10) for transferring digital data from one data bank to another. The system (10) is designed especially for transmitting audio/video signals in digital format from a central processing center (16) to a plurality of cable networks for viewing either instantaneously or in the future. The system (10) incorporates four processing units: a central processing unit (16), a transmission processing unit (18), a receiving processing unit (20), and a master processing unit (22). The central processing unit (16) includes a scripter computer (24) for receiving a video signal (26), converting it to a digital signal (30), and storing the digital signal (30). The transmission processing unit (18) includes a transmission computer (34) and associated transmission hardware (36). The transmission computer (34) will attach a checksum to the end of each packet of information to be sent, along with any other identifying and scheduling information related to that particular file.

Abstract: A modulator circuit comprises an input for receiving an audio frequency (AF) signal, an oscillator circuit for providing a carrier wave signal, a mixer circuit for mixing the AF input signal with the carrier wave signal to provide an AM modulated signal, a switch having a first position in which the AM modulated signal is provided to an output and the switch having a second position in which the AM modulated signal is provided to a vector adding circuit where the AM modulated signal is vector added to the carrier wave signal, and the circuit including phase shift circuitry for shifting the phase of the AM modulated signal prior to vector adding with the carrier wave signal whereby to provide an FM modulated version of the AF input signal on the oscillator carrier wave.

Abstract: A digital FM modulator (10) which functions to modulate a fixed frequency, e.g. RF, reference signal f.sub.r with an incoming AM analog signal v(t) by way of utilization of digital signal processing circuitry (14, 18, 22, 26, 28, 38, 48). The digital FM modulator 10 includes a digital encoder, e.g. a codec 14, which samples the incoming analog signal v(t) at a prescribed sampling rate f.sub.s, and converts it into a digital signal S.sub.D comprised of successive digital words representative of a prescribed parameter (e.g. amplitude) of the analog signal v(t) at corresponding, successive sampling times t.sub.i. This digital signal S.sub.D is a digital data stream which is subsequently conditioned for input to a direct, digital synthesizer (DDS) (48), which, in response to this input, synthesizes an output signal having I.sub.A and Q.sub.A components disposed in phase quadrature relation to each other. The DDS output signal components I.sub.A and Q.sub.

Abstract: An RF modulator comprising an FM modulator supplied with an audio signal, and AM modulator supplied with the FM modulator output and a video signal, an oscillator for generating a sound subcarrier signal, and an oscillator for generating a main carrier signal. Each of the oscillators consists of a VCO with a PLL circuit, and the entire components are composed of a single IC chip so as to be formed into a compact miniature structure. A modified RF modulator includes a PLL circuit for varying the oscillation frequency of a VCO by a variable frequency divider, and a modulation circuit supplied with a modulating signal and the oscillation output of the VCO. The division ratio (integer) of the variable frequency divider is continuously varied, and the reference frequency of a reference oscillator is set to be less than a predetermined channel interval frequency, thereby reducing the frequency error in the modulated signal output.

Abstract: A magnetic induction modulation and frequency multiplication system includes three toroidal coils physically mounted close to one another to provide magnetic flux coupling between them. One of the coils is supplied with a relatively high frequency carrier signal which has been shaped to eliminate one or the other of the positive or negative excursions thereof. A second coil is provided with an audio signal or other suitable input signal. The third coil constitutes the output coil and is utilized to provide signals to a transmitting circuit coupled to a transmitting antenna. The output signal from the third coil constitutes an amplitude modulated and phase/frequency modulated signal directly produced through the mutual inductive coupling of the three coils.