Matsushita Electric Industrial Co., Ltd.

Nippon Hoso' Kyokai

Hideyuki Ikuhara

Akira Usui

Hiroyuki Nagai

Kazuhiko Kubo

Toshihiro Miyoshi

Tetsuo Kutsuki

Yuichi Ninomiya

Masahiro Kawashima

Minoru Miyata

Toshiro Ohmura

Kazuyasu Yamamoto

Tadashi Yamada

Video signal switching circuit especially suitable for high definition

A video signal processing apparatus for processing a video signal including SYNC pulses, a time-compressed color difference and luminance signals, compression factors of those signals being different from each other, the color difference signal and luminance signals being transmitted sequentially for one horizontal line for simultaneously outputting time-reproduced color difference and luminance signals comprises: first and second time-expansion circuits for producing the time-reproduced luminance and color difference signals in response to first and second clocks respectively; a switching circuit for selectively outputting the time-reproduced color difference signal in response to a control signal; a PLL responsive to the video signal including a frequency dividing circuit for producing the first and second clocks, and a synthesized SYNC pulse; and a phase detecting circuit for detecting a phase relation between the video signal and the synthesized SYNC pulse to produce the control signal. When the PLL is out of phase with the SYNC pulse, i.e., not locked, the switch does not transfer the color difference signal from the second time-expansion circuit, preventing time-reproduced signals from producing a double image on a display.

Video signal processing apparatus

An apparatus for receiving and selecting high-definition television signals and NTSC standard television signals includes a high-definition display screen device having an aspect ratio of 16 to 9. The NTSC standard television signals have an aspect ratio which is different than the 16 to 9 aspect ratio of the high-definition display screen device. A first signal converter is for converting the NTSC standard television signals into first quasi-high-definition television signals identifying a first displayed image corresponding in vertical length to a vertical length of the high-definition display screen device. A second signal converter is for converting the NTSC standard television signals into second quasi-high-definition television signals identifying a second displayed image corresponding in horizontal length to a horizontal length of the high-definition display screen device. Switching circuits are provided for selecting one of the high-definition television signals and the first and second quasi-high-definition television signals.

Apparatus for receiving and selecting high-definition television (HDTV)

Disclosed is a local oscillator using a dielectric coaxial resonator (27), which is availably used as a fixed local oscillator in double-spot tuners and CATV converters, and which is arranged so that an AFC voltage is applied to a variable-capacitance diode (23) from an output terminal (E) of a frequency control circuit through a first resistor (35), the variable-capacitance diode having its one end being connected to a center conductor of a dielectric coaxial resonator (27) through a capacitor (25) and its other end being AC grounded, and that a first reference potential (V.sub.A) lower than a source voltage (V.sub.CC) by a predetermined value is given to the variable-capacitance diode (23), the one end of the variable-capacitance diode (23) being connected to the source voltage (V.sub.CC) through a second resistor (22), whereby the voltage impressed across the variable-capacitance diode (23) can be kept constant regardless of a variation in the source voltage to thereby prevent the oscillation frequency from fluctuating.

Voltage controlled oscillator having constant tuning bias voltage

A channel selection apparatus having a double superhet tuner section (15) for converting one of a plurality of television channels contained in an input signal to a fixedly predetermined channel, includes an AFC circuit (11) for producing a frequency control voltage to execute closed-loop frequency control of the second local oscillator (5) of the tuner section while an AFC switch (16) is set in a first condition, whereas when the AFC switch is set in a second condition, a fixed frequency control voltage is applied to the second local oscillator and the frequency control voltage is applied to adjust the oscillation frequency of the first local oscillator (2) of the tuner section such as to compensate for any offset in the transmission frequency of a currently selected channel.

Channel selection apparatus having automatic frequency compensation for

Growing community of inventors

Osaka, Japan

Hideyuki Ikuhara