Electrical audio signal processing systems and devices – Binaural and stereophonic – Broadcast or multiplex stereo
Patent
1984-01-24
1985-09-10
Isen, Forester W.
Electrical audio signal processing systems and devices
Binaural and stereophonic
Broadcast or multiplex stereo
H04H 500
Patent
active
045411093
ABSTRACT:
A pilot signal detecting circuit for use in an AM stereo receiver capable of receiving and demodulating AM stereo signals broadcast according to any of several different AM stereo modulation methods, in which the particular method employed in broadcasting the AM stereo signals is determined by detecting the individual pilot signal and providing an indication of the particular method employed in modulating the broadcast AM stereo signal. Replicas of each of the different pilot signal frequencies in each of the different AM stereo modulation systems are generated and a signal containing the pilot signal is extracted from the demodulated received AM stereo signal. The replicas are compared with the extracted pilot signal to determine the identity of the AM stereo modulation system employed in the received AM stereo signal. A phase-locked-loop is employed to extract the pilot signal from the received signal and a synchronous detector and envelope detector are employed to demodulate the left and right channel stereo signals from the received AM stereo signal. Comparison of the replica and the received pilot signal is performed in identical phase detectors which receive a corresponding replica of the pilot signal produced by another phase-locked-loop and a frequency divider.
REFERENCES:
patent: 4426728 (1984-01-01), Kahn
Shimizu Yoshio
Yokoya Satoshi
Eslinger Lewis H.
Isen Forester W.
Sinderbrand Alvin
Sony Corporation
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