Nec Home Electronics, Inc.

Nippon Hoso' Kyokai

Hitachi, Ltd.

Reiichi Kobayashi

Tetsuro Miyazaki

Tadaaki Tanaka

Fumiyoshi Sasaki

Michio Kobayashi

Tatsuya Shiki

Hiroshi Miyazawa

Shigeo Matsuura

Susumu Takayama

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 video ghost signal canceling circuit which has an adding means for adding a ghost canceling signal to a digital video signal thereby canceling ghost components of the video signal, and a ghost canceling signal generation means for generating a ghost canceling signal in accordance with an output of the adding means. The ghost canceling signal generation means of the present invention comprises a variable delay filter means composed by a parallel arrangement of a plurality of variable delay lines a delay amount of which is controllable from the outside, and a plurality of transversal filters with a coefficient which is controllable, wherein each transversal filter is connected in series to corresponding variable delay line, and the adding means for adding all outputs of the variable delay filter means and for outputting a ghost canceling signal.

Video ghost signal cancelling circuit having variable delay lines

A ghost canceling apparatus provided with a reference waveform Fourier coefficient holding unit in which a normal ghost detection unit holds a Fourier coefficient produced by Fourier transforming a reference waveform; a nearby region Fourier transform unit for Fourier-transforming a nearby region of a reference waveform extracted from the received television signal and a normal Fourier transform unit for Fourier transforming a normal region of the reference waveform extracted from the received television signal; a calculation unit for dividing the output from the normal region Fourier transform unit by the output from the nearby region Fourier transform unit and then for multiplying a Fourier coefficient of the reference waveform Fourier coefficient holding unit; a reverse Fourier transform unit for reverse Fourier transforming the output of the calculation unit; a tap gain supplying unit for supplying the dummy normal ghost producing unit with the output of the reverse Fourier transform unit as a tap gain of the transversal filter.

Ghost canceling apparatus

A ghost canceling circuit comprising a Fourier transforming circuit for Fourier transforming a reference waveform contained in the received television signal while converting the analogue signal into digital form, a device for holding and outputting a reference waveform Fourier coefficient obtained by Fourier transforming the reference waveform contained in the television signal at the transmission side, a signal processing portion in which the outputted reference waveform Fourier coefficient is divided by the result of the A/D conversion, the divided Fourier coefficient is reverse Fourier transformed, and the reverse Fourier transformed Fourier coefficient is supplied to a transversal filter recognizing it as a tap gain.

Ghost canceling circuit

This invention provides a digital color demodulator having: a first phase locked loop circuit which generates an analog subcarrier signal phase locked to the color burst signal; a second phase locked loop circuit which generates an internal system clock signal phase locked to a horizontal period; a Y/C color separation circuit operating under the internal system clock signal; a pair of multiplying circuits, one of which multiplies a digital subcarrier signal, converted from the analog subcarrier signal, with the color signal, and the other of which multiplies the digital subcarrier signal, phase delayed by substantially 90.degree., with the color signal, thereby performing orthogonal demodulation of the signal. The digital processing circuits of this invention are all driven by the internal system clock signal generated by the second phase locked loop circuit.

Growing community of inventors

Osaka, Japan

Reiichi Kobayashi