Patent
1975-01-28
1976-06-22
Olms, Douglas W.
H04H 500
Patent
active
039653021
ABSTRACT:
Improvements in a stereo signal demodulator of a receiver in a four-channel stereo system, in which system upon transmitting four sound source signals (LF, LB, RF and RB) from one station, the transmission is carried out for a synthesized signal composed of a signal in a main channel of (LF + LB) + (RF + RB), a pilot signal, a signal in a first sub-channel consisting of a double side-band signal obtained by modulating an m-multiple frequency-multiplied signal of the pilot signal with a signal of (LF + LB) - (RF + RB), a signal in a second sub-channel consisting of a double side-band signal obtained by modulating the same, m-multiple frequency-multiplied but phase-shifted signal with a signal of (LF - LB) + (RF - RB), and a signal in a third sub-channel consisting of a single side-band signal (SSB or VSB) obtained by modulating an n-multiple (m < n) frequency-multiplied signal of the pilot signal with a signal of (LF - LB) - (RF - RB). The four-channel stereo signal demodulator comprises a circuit for deriving from the pilot signal in said synthesized signal that has been FM-detected by a tuner an m-multiple frequency-multiplied signal of said pilot signal, a signal obtained by phase-shifting said m-multiple frequency-multiplied signal, and an n-multiple frequency-multiplied signal of said pilot signal; first, second and third switching circuits for switching their input signals consisting of said synthesized signal, respectively, under control of the respective three outputs of said signal deriving circuit to demodulate the signals in said respective channels from said synthesized signal; and a matrix circuit having the outputs of said three switching circuits applied to its input for separating and emitting at its output the signals LF, LB, RF and RB. The improvements reside in that a filter and a phase-compensator circuit are electrically coupled in the input circuit for the synthesized signal to said third switching circuit, and in that the outputs of said first and second switching circuits are applied to the input of the matrix circuit through the intermediary of respective delay lines.
REFERENCES:
patent: 3754099 (1973-08-01), Takaoka
patent: 3814858 (1974-06-01), Parker
patent: 3881063 (1975-04-01), Mawake et al.
"4-Channel FM," Radio Electronics, by Len Feldman, Oct. 1973, pp. 40, 41, 42, 98, & 100.
Olms Douglas W.
Sansui Electric Co. Ltd.
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