AM Stereo receiver

Details AM Stereo receiver AM Stereo receiver

1981-11-18

1983-09-13

Hickey, R. J.

Telecommunications

Receiver or analog modulated signal frequency converter

Signal selection based on frequency

455245, H04M 500

Patent

active

044044313

ABSTRACT:
In an AM stereo receiver, a sum signal L+R is generated by subjecting an IF signal to AM detection while a difference signal L-R is generated by subjecting the IF signal to PM detection. The sum signal is applied to one of input terminals of a matrix circuit while the difference signal is applied to the other input terminal via a variable gain circuit. An AM detector for obtaining the sum signal L+R includes a detecting transistor formed in a monolithic integrated circuit and an AGC voltage can be obtained by smoothing the sum signal obtained from the emitter of this detecting transistor. A level shift transistor is formed in the same monolithic integrated circuit, and a voltage virtually equal to a base input d.c. voltage of the detecting transistor of the AM detector is applied to the base of the level shift transistor so that a level shift voltage is obtained from the emitter of the level shift transistor. The variable gain of the variable gain circuit is controlled by a difference voltage between the AGC voltage and the level shift voltage, whereby change in stereo separation due to the temperature dependency of the base-emitter voltage of the detecting transistor can be prevented.

REFERENCES:
patent: 4030035 (1977-06-01), Ienaka et al.
patent: 4349696 (1982-09-01), Akitake et al.
patent: 4375580 (1983-03-01), Sauer

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