电视行同步频率综合器的研制

A Standard Frequency Synthesizer Using TV Line Synchronization Signal

叙述了最新研制的一种标准频率综合器。它通过直接接收中央电视台１、２或４套节目的全电视信号，利用行同步脉冲，便可输出人们常用的１０ＭＨｚ、５ＭＨｚ、１ＭＨｚ、１００ＫＨｚ标准频率信号．经测试，秒级短稳１×１０－９；频率准确度估计可达１０－１２。该设备既能对无线电频率直接进行计量和校准，也可作为标准频率信号源使用。

In this paper, a new standard frequency synthesizer is described. It receives TV signals transmitted from CCTV 1, CCTV 2 or CCTV 4 and outputs the standard freguency signals at the freguencies of 10MHz,5MHz,1MHz and 100KHz.The result of testing shows that: frequency stability is 1×10 -9 /s. Frequency accuracy is estimated as 10 -12 . With this device, a new method for time frequency service is presented here. Starting from Nov.1,1987, the standard time and frequency information has been inserted into TV signals transmitted by CCTV, according to the document Time and Frequency Dissemination via Television Signal (UDC 621. 391. 8. 08 GB7402-87) issued by National Standard Bureau of China in March, 1987. The inserted signals include phase discerning pulse, 1MHz, 1PPS, time code, station ID code, etc. And the subcarrier signal and synchronization system are also controlled by caesium atomic clocks. The device presented in this paper extracts line synchronization signal(15.625KHz)from CCTV signal, then, synchronizes another 15.625KHz signal which is obtained from the 10MHz VCO with temperature compensation(its frequency stability is 10 -8 /s). The synchronization is implemented by a phase locked loop(PLL), the phase difference between these two 15.625KHz signals is converted to voltage signal for adjusting the output frequency of VCO. So, the standard frequency at any frequency bands can be obtained from the output of controlled VCO.