Victor Company of Japan, Limited

Kohei Sasamura

Yukinobu Ishigaki

Teruo Muraoka

Yasuo Itoh

Takaro Mori

Masaru Moriyama

Junsuke Tokumitsu

Isao Ohwaki

A tracking control system comprises a capstan motor for moving a magnetic tape which is at least recorded with an FM signal and a control signal having a constant period, a driving circuit for generating a signal which drives the capstan motor, a control head for reproducing the control signal from the tape in a reproducing mode, heads for reproducing the FM signal from the tape in the reproducing mode, a tracking adjuster for generating a comparison signal, a phase comparator for comparing phases of the reproduced control signal with the comparison signal and for generating a phase error signal which is supplied to the driving circuit to control the driving circuit, a sampling circuit for sampling a signal which is based on the reproduced FM signal with a preset sampling interval, a discriminating circuit for discriminating levels of sampled data obtained from the sampling circuit, and a circuit for generating a control signal based on a discriminated result in the discriminating circuit and for supplying the control signal to the tracking adjuster to automatically and variably control a duty cycle of the comparison signal so that an envelope level of the reproduced FM signal becomes a maximum.

Tracking control system

A video signal processing apparatus for processing a video signal at the time of a special reproduction mode comprises an A/D converter for converting a reproduced video signal obtained by demodulating a frequency modulated signal reproduced from a recording medium during the special reproduction mode into a first digital video signal, a memory having a memory capacity for at least storing the first digital video signal corresponding to one field, a switching circuit for selectively producing the first digital video signal or a second digital video signal read out from the memory, a first circuit for at least generating a first pulse signal having a pulse width corresponding to a predetermined time period and a second pulse signal which determines the read-out timing of the memory, a second circuit for generating a control signal based on the first and second pulse signals for controlling read-out from the memory and causing the switching circuit to selectively produce the second digital video signal during a time period approximately corresponding to the predetermined time period, and a D/A converter for obtaining a reproduced composite video signal from the output digital video signal of the switching circuit.

Video signal processing apparatus for processing video signals at the

A digital signal reproducing apparatus comprises a reproducing circuit for reproducing a recorded unipolar signal from a recording medium, an equalizer for subjecting the reproduced signal to a waveform equalization, a circuit for extracting a timing component having a period which is equal to one bit transmission period of the recorded unipolar signal from an output signal of the equalizer, a circuit for generating one or a plurality of clock signals which are in phase synchronism with the timing component and for forming one or a plurality of control signals by frequency-dividing the timing component by 1/2, a circuit for sampling and holding a peak value of the output signal of the equalizer for every one bit transmission period, a variable resistor for voltage-dividing the sampled and held signal to obtain a reference signal, a delay circuit for delaying the output signal of the equalizer, a comparing circuit for comparing the levels of the output signal of the delay circuit and the reference signal, and a circuit for producing a reproduced unipolar digital signal by controlling the pulse width and the pulse position of the output pulse signal of the comparing circuit by the one or a plurality of clock signals.

Digital signal reproducing apparatus

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.

System for demodulating angle-modulated signals

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 obtain the demodulated signal.

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.

Recording system for a multichannel record disc

A rectifying and smoothing circuit comprises a first rectifier for rectifying an input signal voltage, a first smoothing circuit for smoothing the output voltage of the first rectifier, an attenuation circuit for attenuating the output voltage of the first smoothing circuit, a second rectifier for rectifying voltage passing through the attenuation circuit, a second smoothing circuit for smoothing the output voltage of the second rectifier, and a feedback circuit for feeding back the output voltage of the second smoothing circuit to the first smoothing circuit, the second smoothing circuit, after being charged at a specific voltage, is held at said charging voltage until the output voltage of the first smoothing circuit becomes less than the output voltage of the second smoothing circuit, the output voltage of the second smoothing circuit being derived as the output of the rectifying and smoothing circuit.

Rectifying and smoothing circuit

A multichannel record disc recording system comprises automatic gain control circuits for each of the multichannels a control voltage, representing the phases and levels of the multichannel signals, control the gain of the automatic gain control circuits. An operational circuit at the output of the automatic gain control circuits produces an output sum signal and a difference signal. The difference signal, is angle modulated and multiplexed with the sum signal. The resulting multiplexed signal is recorded on a record disc. Each of the automatic gain control circuits carries out a gain control operation so that the maximum level of the output sum signal does not exceed a predetermined level, and the maximum level of the output signal of the automatic gain control circuit exceeds one half of the predetermined level.

Growing community of inventors

Sagamihara, Japan

Kohei Sasamura