Automatic frequency control circuit selectively using frequency-

Details Automatic frequency control circuit selectively using frequency- Automatic frequency control circuit selectively using frequency-

1994-11-03

1996-08-20

Eisenzopf, Reinhard J.

Telecommunications

Receiver or analog modulated signal frequency converter

Signal selection based on frequency

4551961, 455260, 455264, 455318, H04B 0118

Patent

active

055488110

ABSTRACT:
An automatic frequency control (AFC) circuit receives input signals and generates converted signals by mixing the input signals with a local oscillation signal. An extraction circuit extracts a pilot signal, if present, from the input signals and provides the pilot signal to a switch. A frequency divider divides a frequency of the local oscillation signal output from a voltage control oscillator, and provides the frequency-divided local oscillation signal to the switch. The output of the switch is compared with a reference frequency in a phase comparator which generates a comparison result which controls the voltage controlled oscillator. If the pilot signal is not present, the switch selects the frequency-divided oscillation signal, to construct a phase-locked loop to stabilize the frequency of the local oscillation signal. Alternatively, an AFC circuit includes a frequency divider for selectively dividing a frequency of a pilot signal included in the converted signal. Various frequencies of the pilot signal can be received by altering a division number in the frequency divider.

REFERENCES:
patent: 4247952 (1981-01-01), Shibuya
patent: 4352205 (1982-09-01), Kato et al.
patent: 4691377 (1987-09-01), Yoshihara et al.

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