Abstract: A modulator loop is described having an associated band pass frequency range and including a switching stage having a first delay associated therewith. The modulator loop also includes a modulator stage having a feedback input. The output of the modulator stage is coupled to the input of the switching stage. A first feedback path is coupled between the output of the switching stage and the modulator stage. A notch filter corresponding to the band pass frequency range is coupled between the output of the modulator stage and the feedback input of the modulator stage for compensating for the first delay.

Abstract: A system and method for predistorting a signal which is to be amplified by a non-linear amplifier. The system and method uses additional predistortion circuits to eliminate the predistortion caused by amplifier input circuits and amplifier output circuits. In one aspect of the invention, the system and method uses a frequency response and phase corrector circuit to modify the amplitude versus frequency of the signal independent of phase.

Abstract: A frequency modulator having variable carrier frequency is provided. A VCO frequency-modulates an oscillator input signal using an oscillation frequency set by a set signal as the carrier frequency. A phase/frequency detector outputs phase and frequency differences between a VCO output signal and a reference signal. A filter receives a phase/frequency detector output and generates the set signal. An amplifier generates a pair of output signals whose voltage levels change in opposite directions. A compensation circuit changes the voltage levels of the output signal pair and provides resulting signals to the VCO as the oscillator input signal.

Abstract: A modulated signal, having a varying magnitude signal envelope, is conditioned, such as to facilitate amplification (500). Minimum values are determined values for portions of the signal envelope (520, 530), and a window expansion function applied to scale each portion of the signal envelope having a minimum value below a particular threshold, such that each scaled portion has a new minimum value of at least the particular threshold (535, 540, 550, 555).

Abstract: An FM signal oscillator circuit includes a resonator having a graded- or abrupt-junction variable capacitance diode that is producible through standard IC manufacturing processes but causes an inconstant modulation level. The FM signal oscillator circuit, therefore, is provided with a function of maintaining a constant modulation level irrespective of oscillation frequencies. Namely, to maintain a constant modulation level without regard to oscillation frequencies that change depending on a control voltage applied to the variable capacitance diode, the FM signal oscillator circuit employs a variable gain amplifier whose gain changes in response to the control voltage. The variable gain amplifier amplifies a modulating signal, and the amplified modulating signal is superimposed onto the control voltage.

Abstract: There is disclosed a digital modulator whose modulation parameter can be controlled and in which modulation data or modulated signals are prevented from generating interference signals with adjoining circuits through control when power supply is turned on or system is changed. The digital modulator has a device for detecting that the power supply is turned on, and the transmission data is modulated with fixed data in response to an output of the detecting device for a time required for completing a required system constitution setting. The digital modulator also has a device for detecting the presence of the control for changing the system after the power supply is turned on. In response to an output of the detecting device, modulation is performed with the fixed data for a time from the start till the completion of the setting with a predetermined time added thereto.

Abstract: A modulator loop is described having an associated band pass frequency range and including a switching stage having a first delay associated therewith. The modulator loop also includes a modulator stage having a feedback input. The output of the modulator stage is coupled to the input of the switching stage. A first feedback path is coupled between the output of the switching stage and the modulator stage. A notch filter corresponding to the band pass frequency range is coupled between the output of the modulator stage and the feedback input of the modulator stage for compensating for the first delay.

Abstract: A transmit modulator which uses a quadrature modulator has a predistortion block which produces a predistorted output signal. The predistortion block pre-compensates for errors introduced by the quadrature modulator based on a set of predistortion parameters. The quadrature modulator receives the output signals from the predistortion block. The quadrature modulator up-converts the I and Q channel signals and combines them. In the process, the quadrature modulator introduces errors. In calibration mode, a sinusoidal wave at frequency fcal is applied to the input of the predistortion block and a transformer is coupled to the output of the quadrature modulator. The transformer produces a digital representation of a spectrum of the output of the quadrature modulator converted to baseband. Spurious energy produced by the quadrature modulator errors but reduced by the effect of the predistortion block is generated at fcal and 2*fcal.

Abstract: The present invention relates to a modulator comprising an oscillator which has an oscillation frequency, and a mixer intended to supply a modulated signal with a given output frequency. According to the invention, the nominal oscillation frequency is N times higher than the output frequency, the modulator further including a frequency divider DIV/N intended to receive the output signal of the oscillator and to apply the carrier signal to the mixer, to produce a modulated signal with a first modulation frequency and a parasitic signal with a second modulation frequency.

Abstract: A method of shaping a transmit spectrum of a PCM modem comprising: selecting a first symbol from a first subset of predetermined symbols; converting said first symbol to its linear value equivalent representation; applying said linear value to a transmit shaping transfer function to obtain a shaping function result; and using said shaping function result to choose a second subset of predetermined symbols for transmission of a second symbol. A method of shaping a transmit spectrum of a PCM modem, comprising: converting a symbol to its linear value equivalent representation; and, applying said linear value to a transmit shaping transfer function to obtain a shaping cost function result, wherein said transmit shaping transfer is expressed in the form of H(z)=(1−a1z−1)/(1−b1z−1) wherein: a1 and b1 are coefficients selected to represent the desired spectral shape.

Abstract: A double-balanced modulator in which the bias voltages do not become different by a buffer amplifier or the like connected to the front stage and a carrier wave is not leaked is provided. This modulator comprises a pair of input terminals 2, 3, a pair of preamplifiers 4 for amplifying balance signals supplied to the input terminals 2 and 3, and a double-balanced differential amplifier 23 to which balance carrier signals are supplied and which further amplifies the balance signals that have been amplified by the pair of preamplifiers 4, wherein capacitors 12 are connected in series between the base of a first transistor 7 and one of the input terminals 2, 3 and between the base of a second transistor 8 and the other one of the input terminals 2, 3, respectively.

Abstract: A voltage controlled oscillator circuit (58) having a modulation input port (60) for receiving a modulation input signal through modulation circuit (62, 64, 66, 68) and a frequency resonator circuit (28, 74, 76, 80, 82, 84) operable coupled to the modulation input port (60) for providing a modulation dependent impedance. A semiconductor element (90) has three ports, a gate port (98), a source port (96) and a drain port (92), and the modulation circuit is operably coupled to the gate port (98) of the field effect transistor (90) via a first capacitance (70) and the source port (96) of the field effect transistor (90) via a second capacitance (71). This enables the modulation sensitivity to be substantially independent of temperature variations of circuit elements.

Abstract: A method and apparatus for continuously calibrating the modulation sensitivity of a voltage controlled oscillator (VCO) within a modulator of a transmitter. In accordance with the present invention, the transmitter is coupled to the receiver in order to loop back the transmit signal. The present invention includes a baseband signal generator which generates a reference baseband signal of known amplitude during periods when no other baseband information is being applied to the transmitter by the user. A Signal and Reference Comparison Circuit (SRCC) receives the output from the demodulator and determines whether the VCO within the transmitter has the proper modulation sensitivity. If the modulation sensitivity of the VCO is not within a desired range, then a signal generated by the SRCC is applied to a baseband level control circuit to adjust the level of the baseband signal that is applied to the VCO.

Abstract: A programmable apparatus is disclosed for generating a frequency modulated signal at a selected center frequency in accordance with digital data of at least first and second data levels. The modulating apparatus comprises a modulator having an input and an output and is responsive to an input modulation signal applied to its input for generating at its output the frequency modulated signal at a center frequency dependent on a quiescent voltage appearing at its input. A circuit is provided for sampling and storing a value of the quiescent voltage. An addressable memory stores a plurality of offsets. A programmable adding circuit adds a downloaded offset voltage to the stored value of the quiescent voltage to output a high modulation voltage. A programmable subtracting circuit subtracts a downloaded offset voltage from the stored value of the quiescent voltage to provide a low modulation voltage.

Abstract: A modulator loop designed to operate in a frequency range of interest is described. The loop includes a loop output terminal and a switching stage, the output of which is coupled to the loop output terminal. The switching stage has a first delay associated therewith. The output of a modulator stage is coupled to the input of the switching stage. A first feedback path is coupled between the loop output terminal and the feedback input of the modulator stage. A feedback filter is coupled between the output of the modulator stage and the feedback input of the modulator stage which compensates for the first delay. The feedback filter is operable to transmit frequencies outside the frequency range of interest and attenuate frequencies in the frequency range of interest.

Abstract: A quadrature modulator including two mixers to which two carrier signals are applied and to each of which a modulating signal is applied, output signals of the mixers being applied to a combiner to constitute a modulated signal. A defect estimator for the modulator detects a first signal representative of the instantaneous power of the modulated signal, generates a second signal representative of a reference envelope obtained from the modulating signals, and corrects the amplitude of one of the first and second signals in accordance with the mean amplitude difference observed between this amplitude corrected signal and the other signal. A processor supplies from the observed amplitude difference between the amplitude corrected signal and the other signal, at least one signal relating to the defect.

Abstract: A digital data waveform precompensated for off-chip cable attenuation includes peaks with exponential tails at signal transitions. A driver output stage generating the waveform includes an output transistor pulling the output to a peak voltage level when an input goes high. After a delay, a transistor closes a feedback loop containing a resistive load, exponentially changing the voltage level of the output to a final voltage level. A complementary output transistor pulls the output to a ground voltage level when the input goes low, with a transistor closing a feedback loop containing a resistive load for exponential change of the output to a final voltage level. The separate resistive paths equalize the time constant of the exponential tails despite a difference in the gate capacitances of the output transistors. The received waveform after cable attenuation exhibits pulse shapes closer to the predefined pulse shapes on which a receiver is designed to operate.

Abstract: A calibration system for calibrating a quadrature phase modulator comprises a signal generator for generating a pair of sine-wave signals which are quadrature in phase, an adjusting section for adjusting the amplitude and phase of the pair of sine-wave signals, a DC voltage offset block for adjusting the DC level of the pair of sine-wave signals, and a frequency spectrum analyzer for monitoring the output of the quadrature phase modulator. The output spectrum of the quadrature phase modulator includes three maximal points, two of which are caused by amplitude error, phase error and carrier leakage and minimized by consecutive adjustment in the adjusting block to calibrate the quadrature phase modulator.

Abstract: A digital modulator having a pulse shaping filter which generates and accumulates impulse responses including prior impulse responses and posterior impulse responses to perform a Root-Nyquist raised cosine filtering. The pulse shaping filter includes a dummy accumulation data memory storing dummy accumulation values of prior impulse responses required for initial data transmission. When several initial impulse responses are to be transmitted, for example, on power-up, the impulse responses corresponding to input digital data are generated and added to the dummy accumulation values of prior impulse responses. After the initial transmission, the impulse responses corresponding to input digital data are generated and transmitted without the help of the dummy accumulation values.

Abstract: In a dual mode transmitter for modulating, in a digital mode, an input digital signal and transmitting a modulated digital signal and modulating, in an analog mode, an input analog signal and transmitting a modulated analog signal, a digital modulating section modulates the input digital signal to thereby generate the modulated digital signal, and outputs the modulated digital signal. An analog modulator/carrier generator modulates the input analog signal to thereby generate the modulated analog signal, and outputs it. Also, the analog modulator/carrier generator generates a carrier signal for up-converting the modulated digital signal. The up-converter up-converts, in the digital mode, the modulated digital signal by using the carrier signal and receives, in the analog mode, the modulated analog signal and passes it therethrough.

Abstract: The high frequency circuit includes an oscillator connected in a Colpitts configuration. Negative feedback to the oscillator is applied through an amplifier, both to stabilize the circuit and to permit frequency modulation of the carrier signal generated by the circuit. This feedback incorporates a capacitance to neutralize the Miller effect, thereby enabling it to operate at exceedingly high carrier frequencies. A variation of the circuit permits it to be simultaneously controlled by both a voltage and a current control signal. Also, by applying a frequency modulated carrier signal at a particular node of the oscillator, a demodulated output signal may be obtained.

Abstract: A method and apparatus for producing amplified signals for communications having reduced adjacent channel energy involving generating a first signal having an undesired amount of adjacent channel energy, generating a second signal corresponding to the undesired amount of adjacent channel energy, and subtracting the second signal from the first signal to remove the undesired amount of adjacent channel energy. Several embodiments are disclosed.

Abstract: An estimator for estimating an operating defect in a quadrature modulator, including two mixers to which respective carrier signals are applied, and to which respective modulating signals are also applied. The output signals from the mixers are applied to a summing circuit so as to constitute a modulated signal. The estimator includes detection circuitry for detecting the instantaneous power of said modulated signal; multiplication circuitry for multiplying the detected instantaneous power by at least one of the modulating signals; and integration circuitry for integrating the result of the multiplication and for supplying a signal indicative of the operating defect of the modulator. The modulator is particularly applicable to removing the residual amount of the carrier signals that remains in the modulated signal, and to correcting the quadrature between the signals output by the mixers.

Abstract: A circuit for processing related signal components, such as in-phase and quadrature signal components generated within a modulator, in which a first filter and a second filter are matched such that the gain of each such filter is nearly identical. A modulator is provided having matched filters in accordance with the present invention in which the gain "K" of each filter is equal to 1. By using a filter which has a gain of 1, the gain is removed from consideration when attempting to match the filter response of one filter to another. Furthermore, each filter is relatively simple to implement, having only four resistors, two capacitors, and two operational amplifiers.

Abstract: A method (100), a device (300), and a radio (500) are described for compensating for modulator frequency drift while allowing for data transmission in a half-duplex frequency modulated communication system. An adjustment is made to a premodulation signal in such a way that when it is passed through a frequency modulator to provide a transmitter excitation signal, frequency drift is corrected. Subsequent to determining a training command, the transmitter excitation signal passes through a switch to a demodulator. The demodulator output is averaged and used in the adjustment.

Abstract: A double superheterodyne receiver comprising a pair of first mixer circuits, a pair of second mixer circuits, a demodulator circuit, and a pair of detector circuits. The first mixer circuits are connected in an orthogonal relation to each other and acts to convert a received RF signal into a pair of first intermediate-frequency (IF) signals in the baseband. The second mixer circuits are connected in an orthogonal relation to each other and acts to convert the first IF signals into a pair of second IF signals of a given center frequency. The demodulator circuit arithmetically combines the second IF signals so as to create a third IF signal, and demodulates the original signal from the third IF signal. The output signals from the second mixer circuits are supplied to the detector circuits, which in turn detect the carrier component contained in the output signals. The output signals from the detector circuits are fed to the second mixer circuits.

Abstract: The effects of long-term drift in a local reference oscillator are compensated by dividing the local reference oscillator frequency by one of three divider patterns (nominal ratio, add a cycle, delete a cycle) so that the symbol clock of the remote terminal is equal to the outroute symbol rate. The number of add a cycle and delete a cycle divider patterns are counted and stored. The average of the number of add a cycle and delete a cycle patterns is used to control the transmit frequency of the remote terminal to correspond to the outroute symbol rate. Thus, the clock recovery process generates a frequency calibration number used to track the frequency of the remote terminal local reference oscillator and to adjust the transmit frequency of the remote terminal accordingly.

Abstract: An apparatus and method are provided for increasing the effective Q-value of an oscillator so that the required Q-value can be reached with the use of a low Q-value oscillator. In this apparatus and method, the FM noise is measured at the output of the oscillator by an FM detector and the output of the FM detector is fed back to the control input of the oscillator. By using this negative FM feedback, frequency variations in the oscillator output are suppressed by applying a correction signal at the control input of the oscillator. The amount of suppression depends on the loop gain of the FM feedback loop and the amount of suppression is proportional to the loop gain so that the effective Q-value of the oscillator is proportional to the loop gain.

Abstract: A quadrature modulator multiplies two carriers which are 90.degree. out of phase with each other by a sine component and a cosine component of a baseband signal, respectively, adds the product signals to each other, and amplifies the sum signal to produce a quadrature-modulated output signal. The quadrature modulator includes a phase comparator for detecting a phase distortion suffered when the sum signal is amplified, a first phase controller for correcting the phase of a single carrier generated by a carrier oscillator based on a compared phase output signal from the phase comparator, a phase difference detector for detecting the difference between 90.degree.

Abstract: A system is described which achieves an increased rate of transmission by transmitting multiple symbols in one symbol time. The information in the overlapping symbols can be recovered if the symbol used for transmission is chosen so that a subset of the samples representing the symbol has an inverse. The construction of suitable symbols is illustrated. Effective operation of the system depends on equalizaton which will recover the the baseband signal shape. Methods of equalization are depicted which are suitable for use with this sytem including equalization realized by predistorting the signal at the transmitter so that it arrives at the receiver undistorted. The invention is applied to to baseband and passband systems and the application of predistortion equalization to the fading passband channel is described.

Abstract: In a distortion compensating circuit, an initial value sufficient to provide a distortion compensating effect is previously set in a memory storage for storing distortion compensating data, whereby the convergence time of the distortion compensating effect is shortened.

Abstract: An A/D converter (1) converts analog modulation signals, such as video signals and audio signals, into digital modulation signals. A center frequency data setting circuit (6) outputs center frequency data for setting the center frequency of an FM wave. An operation unit (5) outputs such addition data, on the basis of the center frequency data and average frequency data from a counter circuit (4) as will make the average frequency of the FM wave substantially identical with the center frequency that has been set. An adder (2) adds the digital modulation signals and the addition data, and outputs addition digital signals. A DDS (3) accumulates an addition digital signal in every sampling period supplied from a reference oscillator (7). In the ROM (32) of the DDS (3) are stored sine wave data and the ROM (32), having the accumulated signals as its address input, outputs the sine wave data.

Abstract: A carrier leakage suppression circuit is disclosed which adaptively suppresses carrier leakage in a signal processing device which modulates a carrier signal with an in-phase baseband signal and a quadrature baseband signal to generate a radio frequency (RF) output signal. The carrier leakage suppression circuit operates by imparting a first signature to the in-phase baseband signal and a second signature to the quadrature baseband signal prior to modulation of the carrier signal. In-phase and quadrature carrier leakage components in the RF output signal are isolated and measured by respectively correlating the RF output signal with the first and second signatures. An in-phase offset and a quadrature offset are generated as a function of the measurement of the in-phase and quadrature carrier leakage components. The in-phase baseband signal is combined with the in-phase offset and the quadrature baseband signal is combined with the quadrature offset to thereby suppress carrier leakage.

Abstract: Electronic apparatus generates first and second output signals having a quadrature phase relationship therebetween. A local oscillator signal with a reference phase is applied as an input to first and second signal branches. The second signal branch includes a phase control circuit for subjecting input signals passing therethrough to a determined phase shift. The phase control circuit is responsive to an applied DC control signal to adjust any phase shift error through the phase shift circuit from a predetermined phase shift to assure that the second output signal exhibits the required quadrature phase relationship to the first output signal. A memory/microprocessor combination stores a digital value that is indicative of a DC control signal which must be applied to the control circuit to alter the phase shift through the phase control circuit to the predetermined phase shift. The microprocessor accesses the digital parameter and applies it to the phase control circuit through a digital to analog converter.

Abstract: A quadrature modulator substantially completely compensating a phase error existing between two quadrature carriers by calculating two corrected baseband signals. One corrected baseband signal is generated by adding a common phase component signal and an orthogonal phase component signal after multiplying the common phase component signal and the orthogonal component signal by a first factor a and a second factor b respectively. The other corrected baseband signal is generated by adding the orthogonal phase component signal and the common phase component signal after multiplying the orthogonal component signal and the common phase component signal by the first factor a and the second factor b respectively. The output signal Z of the quadrature modulator is generated by adding both the outputs X and Y of first and second modulating circuits each modulating a respective carrier by a respective corrected baseband signal. If the phase error is .alpha.

Abstract: A self-adjusting quadrature modulator and modulation method improve the accuracy with which digital data is impressed on an RF carrier, which is particularly useful for systems having Viterbi, echo-integrating demodulators and for systems using subtractive CDMA techniques. The method and apparatus involve receiving one's own transmission with a suitable modulation assessment receiver and determining the modulation error relative to the theoretically perfect transmission expected by the receiver. The measured error is used to adjust the modulation to minimize the error. The modulation assessment receiver may use log-polar signal processing to measure phase and (log)amplitude instead of cartesian I and Q components, and then convert to cartesian form. In addition, correction factors determined by the modulation assessment receiver can be directly identified with certain transform components produced by the Fast Walsh Transform.

Abstract: A modulation circuit utilized in a mobile radio communication transmitter includes an amplifier for amplifying a modulation signal and a modulator having a voltage-controlled oscillator for generating a frequency modulation signal corresponding to the modulation signal. An amplifier controller applies a first predetermined constant direct current voltage V.sub.1 to a power source of the amplifier when the frequency of the modulation signal is less than a predetermined frequency f.sub.3, and for a second predetermined constant direct current voltage V.sub.2 to a power source of the amplifier when the frequency of the modulation signal is higher than the frequency f.sub.3. Thus, when the frequency of the modulation signal is less than the frequency f.sub.3, the amplitude of the modulation signal which is added to the voltage-controlled oscillator decreases by a predetermined value compared with the case where the frequency of the modulation signal is higher than the frequency f.sub.3.

Abstract: A digital frequency synthesizer circuit with spur compensation includes a demodulator circuit (118) for demodulating the output signal (116) of the synthesizer's accumulator (108). Demodulator (118) also inverts the signal, and provides an inverted demodulated output signal (142) which is then coupled to the synthesizer clock (124) after passing through a gain stage (122) in order to modulate the synthesizer clock (124) with a compensation signal (146). The compensated clock signal (140) is then sent to accumulator (108) in order to substantially cancel out any jitter in the accumulator's output signal (116). The modulation signal (MOD IN) which is digitally applied to accumulator (108) is applied in analog fashion to the gain stage (122) in order to prevent the desired modulation signal (MOD IN) from being canceled in the output signal (116).

Abstract: A signal processing device for processing an information signal, comprises a frequency modulator arranged to receive the information signal, to frequency-modulate the received information signal and to output a frequency-modulated information signal, a feedback signal generator arranged to receive the frequency-modulated information signal output from the frequency modulator means and to generate a feedback signal therefrom at a phase which is variable to be either in-phase or out-of-phase relative to the received frequency-modulated information signal in accordance with a duty in a high-level period of the received frequency-modulated information signal and at an amplitude which is variable within a range from a zero level to the same level as the received frequency-modulated information signal, and addition circuitry arranged to add the feedback signal output from the feedback signal generator to the information signal received by the frequency modulator.

Abstract: A signal processing device is arranged to form a first output modulated signal by modulating an input information signal in accordance with a modulation carrier signal, to form a second output modulated signal by modulating the first output modulated signal in accordance with a modulation carrier signal which is identical to the above-stated modulation carrier signal, and to correct the input information signal by using the second output modulated signal. The modulation circuit of the device is thus arranged to have a minimal amount of leakage of the modulation carrier signal for the information signal, so that the device can be easily arranged as an integrated circuit.

Abstract: For realizing a highly sensitive and favorably linear frequency modulator stably operating with a small-sized and readily manufactured arrangement, input and output strip electrodes are disposed in face on both ends of a ferri-magnetic film deposited on a magnetic substrate and applied with a DC magnetic field perpendicular thereto, a high frequency electro-magnetic wave being applied through the input electrode, so as to generate a magneto-static forward volume wave propagating through the magnetic film, the propagation phase of which is modulated in response to the intensity variation of the applied magnetic field modulated by a signal, so as to derive a frequency modulated electro-magnetic wave from the output electrode.

Abstract: A diode circuit in which the flicker noise generated by the diode is reduced comprises a diode (D1) connected in series with a resistor (R2) having a by-pass capacitor (C1) in parallel therewith. In one embodiment the side of the diode remote from this resistor (R2) is connected to one input of a DC differential inverting amplifier (A1) via a low pass filter (L1, C2). The amplifier's output is negatively fed back to the junction of the diode (D1) and the resistor (R2) so that the latter forms the amplifier load. A control voltage is applied to the other input of the amplifier of such value as to produce the required diode bias. The basic diode circuit can be extended to perform functions such as amplitude limiting, frequency control and modulation.

Abstract: An adaptive predistortion circuit for a digital transmission system includes a predistortion circuit (52.sub.1, 52.sub.2, 52.sub.3) for predistorting the input data before they pass through a modulator (56) and then through an amplifier (57), and an adaptation circuit (61.sub.1, 61.sub.2, 61.sub.3) for continuously adapting the predistortion circuit to the stream of input data in response to a demodulation of the stream of transmitted data. The predistortion circuit further includes an encoder (51) which, on a first path, in response to digital data a.sub.k, generates digital data b.sub.k which leave a first predistortion circuit (52.sub.1) in a predistorted manner in-phase with the symbol clock, on a second path, digital data c.sub.k which leave a second distortion circuit (52.sub.2) in a predistorted manner phase-shifted by T/3 relative to the symbol clock and on a third path, digital data d.sub.k which leave a third predistortion circuit (52.sub.

Abstract: Briefly, according to the invention, a voltage controlled oscillator 200 having a control input, an information signal input, and an output is disclosed. The voltage controlled oscillator 200 comprises a tank circuit 202 for generating a carrier signal and a modulator 206 for modulating the carrier signal in response to the information signal 210 at the information signal input of the voltage controlled oscillator 200. The voltage controlled oscillator 200 includes a filter 208 coupling the modulator 206 to the tank circuit 202 for rejecting out of band signals from altering the bias point of the modulator 206.

Abstract: A method is described for transmitting digital data with minimum splatter and for recovering the same with a conventional frequency modulated (FM) receiver to obtain data having minimum intersymbol interference. The method utilizes an optimized prototype pulse which has been predistorted to match the inverse characteristics of the post detection low pass filter in a conventional FM receiver. When the optimized electric pulse is received and processed by the post detection low pass filter of the conventional FM receiver, a pulse shape exhibiting minimal intersymbol interference is produced.

Abstract: In a frequency modulation system, a modulating signal is split into its low-frequency and high-frequency components. The low frequency component is used to modulate a carrier signal by conventional means in a first circuit and the low- and high-frequency components are used to narrowband modulate the carrier signal in a second circuit. The outputs of the first and second circuits are combined to provide a frequency modulated signal. The modulating and carrier signals can be binary-coded signals.

Abstract: An amplifier circuit uses a microprocessor to count occurrences of the output stage going into saturation to decide when to control input levels to the amplifier. When the output amplifier stage saturates too frequently, the microprocessor controls a scaling line that effectively attenuates input levels to the amplifier, eliminating saturation levels. When the output stage saturates too infrequently, input levels to the amplifier are increased.

Abstract: The invention relates to a quadrature modulator comprising a circuit for the compensation of a local oscillator leak signal in an output signal of the modulator, which circuit adds different compensation voltages to two modulation signals. To provide an automatic compensation of the local oscillator leak signal, the quadrature modulator of the invention comprises a regulating circuit for the regulation of the intensity of the compensation voltages irrespective of each other on the basis of the correlation between the amplitude variation in the output signal and the corresponding modulation signal.

Abstract: An output having reduced additives phase-noise in at least one defined frequency band is obained from a voltage-controlled oscillator (5) by applying a frequency-modulating signal .omega..sub.m t to the oscillator to produce a sideband within the defined band, the signal having a frequency much higher than the highest multiplicative phase-noise frequency (referred to the unmodulated oscillator frequency) in that band and producing a modulaton index .DELTA.P much greater than the modulation index .DELTA.P.sub.n of the total phase-noise (i.e. additive plus multiplicative)in that band. The oscillator output is then phase-modulated with a signal at .omega..sub.

Abstract: In a modualtion system responsive to a first sampled signal (31) of a first sampling rate for supplying a modulated analog signal to an amplifier having nonlinearities to make the amplifier produce an amplified output signal, a selector (72) selects the first sampled signal and a second sampled signal of a second sampling rate as a selected signal when supplied with first and second control signals, respectively. The second sampling rate is equal to 1/N (N: 2, 3, . . . ) of the first sampling rate. A processing arrangement (36) processes the selected signal with reference to a difference between the selected signal and an additional digital signal (35) to compensate for the nonlinearities to produce a processed signal. The processed signal is modulated into the modulated analog signal. The amplified output signal is demodulated and converted into the additional digital signal by a converter (40).