| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a frequency/phase-locked loop clock synthesizer using a full digital frequency detector and an analog phase detector. <P>SOLUTION: A frequency synthesizer suited to integration in a low-voltage digital CMOS process controls a VCO using a double loop structure including an analog loop and a digital loop. In the digital loop, there is the full digital frequency detector that controls a central frequency of the VCO. In the analog loop, there is the analog phase detector with a charge pump which adds phase coherence to a frequency control loop so that a static frequency error does not occur. Actually, the analog loop reduces noise of a digital logic and the VCO, and digital control supplies frequency hold-over and extremely low bandwidth. The bandwidth of the digital loop is made extremely smaller than that of the analog loop. <P>COPYRIGHT: (C)2005,JPO&NCIPI |
