SYNCHRONOUS VIDEO DETECTOR CIRCUIT USING PHASE-LOCKED LOOP

• Main Authors: TANAKA, TOSHIHIDE, ISOBE, MITSUO, KUTSUKI, TETSUO, YAMAGUCHI, NAMIO
• Format: Patent
• Language: English; French
• Published: 01.10.1985
• Edition: 4
• Subjects: BASIC ELECTRONIC CIRCUITRY; ELECTRIC COMMUNICATION TECHNIQUE; ELECTRICITY; GENERATION OF NOISE BY SUCH CIRCUITS; GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING,BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN ANON-SWITCHING MANNER; PICTORIAL COMMUNICATION, e.g. TELEVISION

In a synchronous video detector circuit using a phase-locked loop, the synchronous detection of a video IF signal is effected with a synchronous carrier signal reproduced by the PLL including a voltagecontrolled oscillator. Each of a phase comparator of the PLL and a synchronous video detector has its input terminal connected to an output terminal of a video IF amplifier by untuned coupling, and arranged on the output side of the synchronous video detector is a phase-locked mode detector for detecting that the PLL is in its phase-locked mode. The phase-locked mode detector is adapted to control the band width of a low-pass filter of the PLL in either a narrow band mode or a wide band mode and the low-pass filter is controlled to operate in the narrow band mode only when the PLL is in the phase-locked mode of operation. The black and white noise included in the output signal of the synchronous video detector are both cancelled by a noise cancellation circuit including a black noise detector for pulse noise cancellation purposes.