Automatic frequency control circuit in a stereo FM radio receive

Details Automatic frequency control circuit in a stereo FM radio receive Automatic frequency control circuit in a stereo FM radio receive

1985-02-05

1986-10-28

Isen, Forester W.

Electrical audio signal processing systems and devices

Binaural and stereophonic

Broadcast or multiplex stereo

381 13, H04H 500

Patent

active

046203150

ABSTRACT:
An automatic frequency control circuit is used in an FM stereo radio receiver which includes an intermediate frequency amplifying and detecting circuit producing an output for driving a signal meter and includes a multiplexer, so that the multiplexer effects controls to reduce noises in stereophonic and monophonic reception responsively to the signal meter driving circuit by changing its separation ratio and attenuation ratio. The circuit comprises: an adder which adds a dc voltage obtained by rectifying and smoothing ac components in the signal meter driving voltage to a dc voltage obtained by rectifying and smoothing noise components in an output from a noise cancellor; a comparator which compares the sum voltage from the adder with original dc components in the signal meter driving circuit; and a subtraction voltage generator which produces a subtraction voltage responsive to the difference between the compared two voltages, so that the noise reducing controls are effected responsively to the subtraction voltage.

REFERENCES:
patent: 3823268 (1974-07-01), Modafferi
patent: 4157455 (1979-06-01), Okatani et al.
patent: 4356350 (1982-10-01), Ienaka
patent: 4416024 (1983-11-01), Ugari et al.
patent: 4419541 (1983-12-01), Kishi et al.
patent: 4480335 (1984-10-01), Kishi

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