发明授权
US5329250A Double phase locked loop circuit 失效
双锁相环电路

Double phase locked loop circuit
摘要:
A frequency of a first VCO (12) for generating a carrier of a video IF signal is set by using a frequency of a second VCO (15) as reference. The oscillation frequency of the second VCO (15) is controlled in response to the phase difference between an output signal of the first VCO (12) and the video IF signal. As a result, the output signal phase of the first VCO (12) is adjusted, and the output signal is locked to a carrier frequency of the video IF signal. Thus, the oscillation frequency of the first VCO (12) can be set automatically. Further, a signal for the phase difference between the output signal of the first VCO (12) and the video IF signal is also applied to the first VCO (12), thereby improving the stability of circuit operation.
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