Sharp Kabushiki Kaisha Corporation

Tokyo Shibaura Denki Kabushiki Kaisha

Nippon Hoso' Kyokai

Soichi Iwamura

Hiroaki Nogami

Tadashi Itsumi

Satoshi Murakami

Yoshio Nishi

Norikazu Sawazaki

Eiichi Takakura

Naoki Koide

Yasuaki Nishida

Norio Endo

Masaharu Watanabe

Junichi Aoki

Masakazu Ishikawa

Toshimi Yamato

Mitsuhiro Suga

A magnetic reproduction apparatus which uses a magnetic recording medium on which frequency-modulated signals produced by frequency-modulating a carrier with video signals are recorded, and demodulates reproduced signals from the magnetic recording medium into the video signals. The apparatus includes a frequency convertor for causing the reproduced signals to shift to a higher frequency region and a pulse-count-type FM demodulator for demodulating the reproduced signals which have shifted to the higher frequency region into the video signals. This arrangement restrains the mixing of the reproduced signals in the video signals. Therefore the video signals are reproduced with lessened waveform distortion, achieving a high-quality image.

Magnetic reproduction apparatus for reproducing a video signal

A magnetic recording-reproduction apparatus records and reproduces a wide-band video signal without a color burst signal. For this purpose, a two-step phase resetting operation is conducted on the FM carrier at the front porch and the horizontal sync pulse of the video signal so as to permit those phases to coincide with reference phases. A synchronizing panel clock generator generates the first reference signal with the first FM frequency corresponding to a peak level of the horizontal sync pulse and the second reference signal with the second FM frequency corresponding to a front porch level. In this case, the reference signals are phase-synchronous with each other at the leading edge of the horizontal sync pulse, and each of the FM frequencies is set to be an integer multiple of the horizontal scanning frequency. In another arrangement, a secondary FM carrier whose frequency has been shifted to a low-band is formed by generating a frequency conversion signal synchronous with the horizontal sync pulse and combining the phase-reset FM carrier with the frequency conversion signal. Either of the above arrangements can eliminate unwanted higher harmonic wave components and transient distortions in the frequency-demodulated output, thereby improving the image quality.

Recording-reproduction apparatus applying double reset to the phase of

An FM carrier is FM-modulated with a video signal for recordal on a magnetic medium. The phase of the FM carrier corresponding to a tip portion of a horizontal synchronizing pulse in the video signal is reset to, and the phase is fixed at, a reference phase at a leading edge of the horizontal synchronizing pulse and is fixed during every period of the horizontal synchronizing pulse width. In reproducing the video signal, the FM carrier, with its frequency doubled, is demodulated by a pulse count type FM demodulator having a frequency-doubling function. The FM carrier is always maintained in phase with the horizontal synchronizing pulse in the video signal, so that beat stripes or moire do not appear on the reproduced picture, and interference due to the leakage appears as reproduced picture distortion in correlation with the video signal. A reference burst signal necessary to a time base correction is extracted from the reproduced FM carrier.

Magnetic reproducing apparatus for reproducing a video signal from a

A magnetic reproducing head amplifier includes a differential amplifier referred to as one of these three types: a balanced input type, a balanced output type, or a balanced input/output type. The amplifier has at least one positive feedback circuit for passing a positive feedback current to the differential amplifier, and at least one negative feedback circuits for passing a negative feedback current to the differential amplifier and is configured so that a positive feedback and a negative feedback are simultaneously performed by the positive feedback circuit as well as the negative feedback circuit. A resonance peak characteristic at the input part of the differential amplifier is dumped by the negative feedback current, and therefore a frequency characteristic as well as a group delay characteristic of the output of the differential amplifier becomes flattened. Moreover, the use of the positive feedback current from the positive feedback circuit permits the charging current from the signal source to the input capacitance of the differential amplifier to be reduced, that is to say, an effective input capacitance is reduced, and thereby a resonance frequency at the input part of the differential amplifier can be shifted to the vicinity of the upper limit of the transmission band. Consequently, a stable amplification operation can be achieved for FM carriers for carrying wide frequency signals, such as HDTV signals.

Magnetic reproducing head amplifier

An FM modulator includes a base clock generating circuit (7) receiving an incoming video signal for generating an AFC reference frequency signal having a frequency and phase corresponding to a horizontal synchronizing signal of the incoming video signal, a first carrier reset pulse having the same frequency as the horizontal synchronizing signal and a second carrier reset pulse whose frequency is an integer mutliple of that of the horizontal synchronizing signal. The second reset pulse is generated at a timing speed lagged behind the first reset pulse. The FM modulator further includes an adder (3) for adding the first reset pulse to the incoming video signal for lowering the DC level at the leading edge portion of the horizontal synchronizing signal, and an oscillator (9, 9a, 9b, 10, 10a, 10b) whose oscillation frequency is changed dependent on the DC level of the output signal from the adder to produce a carrier FM modulated by the video signal. The oscillator is reset by the second reset pulse.

Carrier reset FM modulator and method of frequency modulating video

An improved jitter detecting method and an apparatus thereof, for detecting jitter generated in a reproduced video signal of a VTR or video disc wherein a frequency-modulated carrier of a video signal is recorded by synchronizing the leading edge of a sync signal with the phase of the forefront carrier of a constant frequency carrier train corresponding to a sync tip for every horizontal period at the time of frequency-modulation. From the reproduced frequency-modulated carrier, the phase-reset constant frequency carrier train is utilized as a reference burst signal, thereby to be capable of removing a time-base error by detecting a specific zero-crossing timing of the carrier burst through a bandpass filter based on the trailing edge of a frequency-modulated sync signal during reproduction.

Circuit for detecting and compensating for jitter produced by a

In a method for multiplexing the transmission of audio and video signals, the video signal is separated into a luminance signal and a chrominance signal. The luminance signal is then modulated, and the chrominance signal is balanced-modulated with a low-frequency carrier. The chrominance signal is then converted to a lower frequency. The audio signal, frequency-modulated luminance signal and frequency-converted chrominance signal and frequency-converted chrominance signal are multiplexed by frequency division to be transmitted across telephone cable. Consequently, in comparison with the conventional transmission method which executes direct frequency modulation of the video signal, the band-width of the frequency-modulated luminance signal becomes narrower to eventually facilitate multichannel transmission. The harmful influence from interference from external radio waves or from metallic members used to fix the cable is removed on the receiver side. Accordingly, satisfactory picture transmission can be performed without the necessity of any additional coaxial cable for video signal transmission.

Multiplex transmission of audio signal and video signal through inhouse

A power transmission system in which a power sending terminal is connected to a power receiving terminal via a communication cable made of a pair of parallel PVC-coated solid or stranded wires, the power sending terminal superposing DC-power on multiplex signals and transmitting the DC superposed multiplex signals through the communication cable to the power receiving terminal where DC power is separated from the multiplex signals to operate remote equipments.

Power transmission system

An information recording medium comprises a silicon substrate, a silicon dioxide film formed on one principal surface of the semiconductor substrate and a silicon nitride film formed on the silicon dioxide film. A recording electrode stylus is moved relative to and along the surface of the silicon nitride film while applying a recording signal voltage between the stylus and substrate, thus causing charges corresponding to the recording signal voltage to be passed through the silicon dioxide film by the tunnel effect and stored in the silicon nitride film.

Growing community of inventors

Fuchu, Japan

Soichi Iwamura