DR. WEI CHIA CHEN, MD
Osteopathic Medicine at Bascom Ave, San Jose, CA

5072195, Dec 10, 1991

Apr 5, 1990

7/505851

Andrew C. Graham - Sunnyvale CA
Mark E. Fitzpatrick - San Jose CA
Wei Chen - San Jose CA

Gazelle Microcircuits, Inc. - Santa Clara CA

H03L 7093, H03L 723

331 2

A phase-locked loop responsive to both phase and frequency difference between the incoming signal and the feedback signal is provided. Using a reference signal, this phase-locked loop accepts a wide range of frequencies similar to a phase-locked loop having a phase frequency detector, and also achieves the noise performance of a phase-locked loop having only a simple phase detector. In one embodiment, the phase-locked loop is a combination including first and second phase-locked loops. The reference signal is provided to the first phase-locked loop, which includes a phase frequency detector. This first phase-locked loop is used to control a second phase-locked loop, which includes a phase detector. A voltage clamp can also be provided to enhance the ability to lock a signal among several signals, or from a noisy background.