Abstract: An FM wave received by an antenna is fed via an AGC circuit to a first FM demodulator and to a compensation signal generator which includes an envelope signal generator, a capacitor, a function generator, an analog multiplier, an SSB modulator, and a second FM demodulator so that the output signal of the compensation signal generator is added to the output signal obtained by the first FM demodulator to offset the multipath distortion contained in the received FM wave.

Abstract: A crosstalk cancellation circuit includes a pair of input terminals to which interference affected FM signals are applied and a pair of output terminals from which distortionless demodulated signals are delivered. For each transmission channel an envelope detector is provided which is connected to the input terminal to detect the envelope of the FM signal. A closed-loop feedback circuits are cross-coupled across the output terminals to process the signals thereat with the detected envelopes to derive an offset signal for each channel, which is combined with a frequency-demodulated signal of the FM signal of each channel.

Abstract: A phase tracked loop frequency demodulator having a phase comparator receptive of a frequency modulated signal and a peak-shifting filter for imparting a constant phase shift of 90.degree. over the full range of its instantaneous frequencies in response to a feedback control signal to permit the phase comparator to compare the non-phase shifted and phase shifted signals. The carrier frequency components of the output from the comparator are eliminated by means of a second filter to derive a demodulated signal which is used as the control signal. In order to eliminate high frequency limitations of the peak-shifting filter, this filter is comprised of a variable reactance element and a complementary reactance element so connected thereto to form a resonant circuit which possesses a quadratic frequency response characteristic with a resonant peak at the upper or lower frequency end of the passband.

Abstract: A system comprising a demodulator for demodulating an input FM signal which has been subjected to interference by another FM signal, an envelope detector for detecting the envelope of fluctuation of the amplitude of the input signal, an AGC circuit for controlling the level of the input signal supplied to the envelope detector, a capacitor for passing only the AC component of the output of the envelope detector, a circuit having a transfer characteristic of a hyperbolic function and converting the waveform of the AC component, an analog multiplier supplied at its x input terminal with the output of the waveform converting circuit and producing a distortion cancellation signal, a first operation circuit supplied with the output signal of the demodulator and with the distortion cancellation signal and carrying out an operation such as substantially cancelling the interference distortion of the demodulated signal with the distortion cancellation signal, a delay circuit for delaying the output signal of the first

Abstract: A system for removing interference distortion in the demodulated signal of a frequency-modulated signal comprises a demodulator for demodulating an input frequency-modulated signal Ca(t) which has been subjected to interference by another frequency-modulated signal, and thereby obtaining a demodulated signal e.sub.o (t), a first analog multiplier for obtaining a signal in which the input frequency-modulated signal is squared, a low-pass filter supplied with the squared signal and detecting an envelope of the input frequency-modulated signal in square characteristics, and thereby producing as output a squared envelope signal {Env(t)}.sup.2, a second analog multiplier supplied with the demodulated signal e.sub.o (t) from the demodulator and with the squared envelope signal {Env(t)}.sup.2 from the low-pass filter, and thereby producing as output a signal e.sub.oa (t) of the product of both signals, a DC blocking capacitor for suppressing DC component of said squared envelope signal {Env(t)}.sup.

Abstract: In a record disc recording system for recording a signal f(t), the cutter stylus has a cutting angle .theta. and operates responsive to a signal to be recorded on a record disc. A tracing and tracking distortion compensation circuit operates, upon being supplied with the recording signal f(t), to produce an output signal T.sub.p.sup.-1 {f(t)} as expressed by the following equation, and to supply the same as the signal to be recorded by the cutter stylus. ##EQU1## where R IS THE RADIUS OF THE TIP OF A REPRODUCING STYLUS TO BE USED FOR REPRODUCING THE RECORDED SIGNAL FROM THE DISC,V is the relative linear velocity of the reproducing stylus relative to the sound groove of the record disc, ##EQU2## The cutter operates responsive to the signal T.sub.p.sup.-1 {f(t)}. The reproducing stylus reproduces the signal thus recorded without tracing and tracking distortion.

Abstract: The inventive system demodulates angle-modulated signals. A tracking band-pass filter responds to an input angle-modulated wave signal. The tracking filter has a pass band with a center frequency controlled by a control signal. A first amplitude limiter limits the amplitude of the input angle-modulated wave signal. A differentiation circuit establishes a 90.degree. phase difference between a signal passing through the tracking band-pass filter and a signal passing through the amplitude limiter. A phase comparator responds to an input with the two signals with a 90.degree. phase difference therebetween and produces an output error signal in accordance with this phase difference. This output error signal is supplied as the control signal to the tracking band-pass filter. This output error signal is also passed through a low pass filter to produce the demodulated signal.

Abstract: A multichannel record disc recording system uses two channels of direct wave sum signals and two channels of angle-modulated wave difference signals which are multiplexed and recorded in one sound groove on a record disc. During recording, a tracing distortion compensation means imparts a reverse distortion which cancels the tracing distortion produced, with respect to the sum signals, during reproducing. Since the compensation means is in the transmission paths of the direct wave sum signals, the reverse distortion is only imparted to the direct wave sum signals. Also, phase correction signals are provided.

Abstract: A record disc recording system comprises a circuit for producing a signal which is substantially 2V.sup.2 . a, where; V is the relative velocity between a cutter head and a disc, and a is a specific coefficient, which varies in accordance with the traversing of the cutter head over the disc. A circuit produces a distortion signal {f'(t)}.sup.2 /{2V.sup.2. a - f"(t)} (wherein .vertline.2V.sup.2. a.vertline.>.vertline. f"(t).vertline.) responsive to an original signal f(t) and to the signal 2V.sup.2. a. Another circuit produces a recording signal g(t) with distortion (where g(t) = f(t) + {f'(t)}.sup.2 /2 {2V.sup.2. a - f"(t)}) responsive to the original signal f(t) and to the distortion signal {f'(t)}.sup.2 /{2V.sup.2. a - f"(t)}. A cutter head records the signal g(t) on a record disc.

Abstract: A band-pass filter comprises a delay circuit comprising a plurality of unit delay elements connected in cascade arrangement and receiving as input a signal including a frequency modulated signal and a coefficient summing circuit for carrying out coefficient summing of the outputs of specific delay units of the delay circuit and producing as output the frequency moudlated signal which has been band-pass filtered. This band-pass filter has a transmission characteristic representable byH(j.omega.) = [ 1 - a(.omega. - .omega..sub.o).sup.2] e .sup.-.sup.j.sup..omega..sup..tau.d ,where:a is a constant imparting an attenuation characteristic of the filter;.omega..sub.o is an angular frequency of a carrier wave of a frequency modulated signal and a center angular frequency of the band-pass filter; and.tau.d is a delay time of the band-pass filter.

Abstract: A multichannel record disc reproducing system and apparatus comprises a phase-locked loop for demodulating an angle-modulated wave signal in a multiplexed signal picked up from a multichannel record disc. A synchronous detector compares the phases of the angle-modulated wave signal and an output signal of a voltage-controlled oscillator in the phase-locked loop. The detector produces an output signal when there is a noise component in the angle-modulated wave signal. A circuit, controlled by the output of the synchronous detector, provides a demodulated output signal having at least one attenuated frequency band, in which a noise component is greatly reduced.