| 摘要 |
PURPOSE:To attain broad band phase synchronization, to simplify a circuit, to improve the quality of picture with a low cost and to quicken the picture output by adding a local oscillator, a frequency divider, an HPF, an LPF and two mixers. CONSTITUTION:A signal having a frequency fL, from a local oscillator 60 is subjected to 1/N frequency division by a frequency divider 62 and the signal of fL/N is inputted to a 1st mixer 64 and mixed with a input signal fi from a device 66. Then the signal of frequency fi+ or -fL/N is filtered by the HPF 68 and the frequency signal of fi+ or -fL/N is inputted to a N-multiple phase locked loop circuit (NPLL) 70, where the signal is multiplied by N and the signal of frequency Nfi+fL is sent to a 2nd mixer 72. Then the signal is mixed with the signal from an oscillator 60 by a mixer 72 and the signal of frequency Nfi+fL+ or -fL is inputted to the LPF 74, the clock signal of frequency Nfi without frequency bias is outputted from an output terminal 76. Thus, the broad band phase synchronization is attained, the circuit is simplified, the picture quality is improved and the picture output is quickened with low cost. |
