| 摘要 |
PURPOSE:To obtain video detection signal with less phase jitter in terms of a television receiver by detecting the frequency difference between the carrier frequency of a video intermediate frequency signal and the oscillation frequency of a voltage control oscillator in a phase synchronizing loop and using the detected signal for adjusting frequency. CONSTITUTION:When the output frequency of a voltage controlled oscillator 37 for comprising the phase synchronizing loop (PLL) is far different from the carrier frequency of a video intermediate frequency signal, a phase detection output passed through a low-pass filter 36 is approximately zero, the voltage controlled oscillator 37 is in the self-travel oscillated state. With the aid of an automatic frequency adjusting circuit (AFT) 34, the frequency difference between the output frequency of the voltage controlled oscillator 37 and carrier frequency of the video intermediate frequency signal is converted into a voltage or current and outputted as an AFT signal. As a result,the automatic frequency adjustment is executed so that the carrier frequency of the video intermediate frequency signal can coincide with the output frequency of the voltage controlled oscillator 37. |
