Hitachi, Ltd.

Nippon Hoso' Kyokai

Shigeo Matsuura

Toshinori Murata

Eisaku Akutsu

Takeshi Saitoh

Masaki Noda

Keiro Shinkawa

Hiroshi Hatashita

Mitsuhisa Shinagawa

Hiroshi Miyamoto

Hiroshi Miyazawa

Hiroshi Harada

Toshio Nagashima

Kazuhiro Kaizaki

Chuichi Sodeyama

Yasuhiro Yakushiji

Sadao Kubota

Minoru Moteki

Reiichi Kobayashi

Susumu Takayama

Ikuo Yuki

Yoshiharu Umemura

Masakazu Kondo

Uji Ito

Masao Usui

Shigehiro Ito

For canceling ghost components disturbing a received picture signal waveform in the television transmission such as the television broadcast, ghost components of a reference pulse signal inserted at a central portion of a horizontal scanning period in a vertical blanking period of a picture signal is detected and then the received picture signal is processed such as those ghost components of the inserted reference signal are canceled by each other. In this signal processing, an auxiliary reference signal, the waveform and/or the level of which differ from those of the principal reference signal, the latter being occasionally almost zero, is inserted in a horizontal scanning period delayed from the principal reference signal by a repetition period after the lapse of which regular controlling signals such as synchronizing signals and color bursts having just the same waveform, level and phase reappear. In the differential signal waveform between received picture signals respectively neighboring both of reference signals, regular controlling signals are canceled by each other, while ghost components consisting of remaining waveforms except the difference between both of reference signals only are left, so as to facilitate the accurate detection of ghost components even exceedingly delayed over one half of a horizontal scanning period.

Method of detecting signal waveform disturbance in received television

A noise reduction circuit for reducing noise in video signal comprises delay circuits for delaying an output video signal for delay time 2S and H-S (H denotes one horizontal scanning period and S denotes a half of one period of the color subcarrier), an average circuit for averaging the outputs of the delay circuits, a subtraction circuit for subtracting the output of the average circuit from an input video signal, an attenuation circuit for attenuating the output of the subtraction circuit, an addition circuit for adding the output of the attenuation circuit to the input video signal, and an edge detection circuit for detecting the edge of pattern in the input video signal. The attenuation factor of the attenuation circuit is set into zero when the edge of pattern is detected.

Noise reduction circuit

A receiving circuit for receiving an FM-modulated television signal with an energy dispersal signal superposed thereon is used for a television receiver for receiving the FM-modulated television signal. The receiving circuit is provided with a triangle wave signal generator for generating a triangle wave signal in synchronism with a vertical synchronizing signal. The energy dispersal signal superposed on the FM-modulated television signal is suppressed by frequency modulating an oscillation signal of a local oscillator by the triangle wave signal obtained.

FM television signal receiving circuit

A remote control signal reproducing circuit for use in a remotely-controlled receiver which receives a modulated transmission signal subjected to a pulse modulation, reproduces an original remote control signal form the received modulated transmission signal, and judges the reproduced remote control signal for effecting predetermined control operations based on pulse counts obtained during three predetermined successive time intervals. A remote control signal is delivered if the pulse count obtained in the first time interval exceeds a first level. Judgement of the remote control signal is stopped when the number of pulses counted during the second and third time intervals is below or above predetermined numbers respectively. The circuit functions to eliminate noise pulse.

Remote control signal reproducing circuit

A double-superheterodyne tuner for a television receiver comprises a tunable oscillator, a fixed oscillator, two mixer stages and a band-pass filter between the mixer stages, and operates at a GHz intermediate frequency between the mixer stages. The two oscillators and the bandpass filter each includes a microstrip line resonator formed in a dielectric body having substantially the same dielectric constant and dielectric constant temperature coefficient to each other, thereby compensating the variation of the resonant frequency in the resonator due to an ambient temperature variation.

Wide-band tuner having a temperature-compensated microstrip resonator

A receiving circuit for a television receiver for receiving an FM-modulated television signal is disclosed, in which the oscillation frequency of a local oscillator circuit is fine adjusted by a voltage of a sync signal of the FM-modulated television signal thereby to receive the television signal properly.

FM Television signal receiving circuit

There is disclosed an electronic selection apparatus comprising a surface acoustic wave comb filter, in which the local oscillator frequency of an electronic tuner is swept up to a frequency higher than a peak frequency of the surface acoustic comb filter corresponding to a desired channel number (an upward direction), and then swept toward the opposite direction (a downward direction) until a predetermined number of peaks of the comb filter is counted while checking the presence of an AFC signal, whereby an erroneous tuning operation may be prevented, provided that the signal of the desired channel is present within a predetermined range in the vicinity of the receiving frequency of the desired channel.

Electronic channel selection apparatus with surface acoustic wave device

In a channel selection apparatus for a television receiver or FM radio receiver having an electronic tuner, a local oscillation signal of the electronic tuner having a local oscillator which is swept by a voltage sweeping circuit is passed through a comb-shape filter having a SAW element. Peak outputs from the comb-shape filter are counted by a presettable counter. When the count reaches a preset count, the sweeping operation of the voltage sweeping circuit is stopped to select a desired channel. A portion of the peaks of the comb-shape filter characteristic is attenuated and a gap appearing at the attenuated portion is detected by the frequency sweep of the local oscillation signal with a change in time interval. The detection signal is compared to discriminate the first pulse necessary for the channel selection.

Channel selection apparatus

A synchronizing signal discrimination circuit for use in a channel selection apparatus having a preset function of a television receiver is disclosed. The circuit has a function to discriminate a periodic and continuous signal and a non-periodic and one-shot signal to distinguish a synchronizing signal from a noise. The present synchronizing signal discrimination circuit determines a time period from the application of a first input signal to the input terminal to the application of a second input signal to the input terminal by the first time interval signal and the second time interval signal to detect only the periodic and continuous signal as the synchronizing signal.

Synchronizing signal discriminator for use in channel selection

A channel indicator suitable for use in a television receiver and an FM receiver each having an electronic tuner is disclosed in which a channel number now being received can be automatically indicated by counting the number of those local oscillation frequencies corresponding to respective channels which the local oscillation frequency of the electronic tuner has passed prior at the arrival to a desired value. Means for compensating for irregular frequency channel intervals and temperature variations are included.

Channel indicator

A channel selection apparatus comprises a sweep control voltage generator driven by a circuit for sweeping the local oscillation signal frequency in an electronic tuner. The local oscillation signal frequency sweeping circuit includes an arrangement for increasing the rate of sweeping the local oscillation signal frequency only when the latter is being changed not in the vicinity of a destined frequency. The apparatus may further comprise another arrangement for preventing an eventual excessive sweeping beyond the destined frequency.

Channel selection apparatus tunable to destined frequency in short time

A high-frequency input circuit suitable for use in a television receiver, which includes a tuning circuit which can operate with a reduced loss and can be tuned to signals in, for example, the VHF and UHF bands at the same time. The high-frequency input circuit provides an integrated tuner capable of receiving all the signals within the range from the VHF band to the UHF band.

Tunable high-frequency input circuit

A digital-to-analog converter of a pulse width modulation type in which a single counting cycle of a clock pulse counter is divided into 2.sup.m elementary periods where m represents a selected number of less significant bits of a digital input data to be converted into analog quantity and elementary pulses in number determined in dependence on the logic values of the more significant bits are distributed among the elementary periods, while supplementary elementary pulses are produced in the elementary periods selected in dependence on the logic values of the less significant bits of the digital input data. These elementary pulses are integrated for every elementary period and the integrated output value is converted into a corresponding DC analog output signal.

Digital-to-analog converter of the pulse width modulation type

An automatic channel selection apparatus comprises an electronic tuner having a local oscillator an oscillation frequency of which is controlled by an applied voltage, a voltage sweep circuit for sweeping the voltage to be applied to the local oscillator, means for deriving from an output of the local oscillator, signals of different phases and combining those signals, a detector for envelope-detecting an output of the deriving means and means for counting the number of varying cycle periods in the output of the detector which changes periodically each time the oscillation frequency of the local oscillator changes by a given amount which is inversely proportional to the phase difference to change a tuning frequency of the electronic tuner by a specified amount.

Automatic channel selection apparatus

A search tuning type channel detector system for television receivers. When AFC voltage of a tuner has attained a first predetermined voltage level, frequency sweeping direction for tuning is reversed and stopped thereby to tune the tuner at an optimum tuning frequency. Means are provided to allow the inversion as well as stoppage of the frequency sweeping only when AFC voltage has attained a second predetermined voltage level, thereby to exclude possible erroneous operation due to noise or the like spurious signal components.

Growing community of inventors

Yokohama, Japan

Shigeo Matsuura