Phase locked loops including input amplitude control

Details Phase locked loops including input amplitude control Phase locked loops including input amplitude control

1998-02-10

1999-08-31

Callahan, Timothy P.

Miscellaneous active electrical nonlinear devices, circuits, and

Signal converting, shaping, or generating

Synchronizing

327159, 327158, 327162, 331 2, 331 18, 331 25, H03B 304

Patent

active

059458542

ABSTRACT:
Phase locked loops include a controlled oscillator that is responsive to a control signal, to generate an output signal, the frequency of which is a function of the control signal. A phase detector is responsive to a reference frequency input signal and to the output signal, to produce an error signal. A loop filter filters the error signal, to thereby produce the control signal. A bandpass filter is responsive to the error signal, to produce a filtered error signal at twice the frequency of the reference frequency, and an envelope detector is responsive to the filtered error signal to sense the amplitude of the filtered error signal. A variable attenuation circuit is responsive to the envelope detector output, to variably attenuate a phase locked loop input signal based on the amplitude of the filtered error signal, and thereby produce the reference frequency input signal.

REFERENCES:
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patent: 4954788 (1990-09-01), Leis et al.
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patent: 5202924 (1993-04-01), Richards, Jr.
patent: 5408202 (1995-04-01), Shirazi et al.
patent: 5631601 (1997-05-01), Horsfall et al.
patent: 5642082 (1997-06-01), Jefferson

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