Electrical audio signal processing systems and devices – Binaural and stereophonic – Broadcast or multiplex stereo
Patent
1985-03-05
1987-07-14
Isen, Forester W.
Electrical audio signal processing systems and devices
Binaural and stereophonic
Broadcast or multiplex stereo
381 13, H04H 500
Patent
active
046807926
ABSTRACT:
In a demodulator comprising an indicator (31) for indicating either stereo reception or monaural reception, an indicator circuit (30) is used to cancel a pilot signal included in a stereophonic signal and to produce a drive signal for driving the indicator. The indicator circuit comprises a negative feedback loop formed by an adder circuit (41), a phase detector (43), and a cancellation circuit (45). The cancellation circuit supplies the indicator and the adder circuit with the drive signal and a cancelling signal synchronized with and approximate to the pilot signal, respectively. The adder circuit substracts the cancelling signal from the pilot signal to deliver an intermediate signal to a multiplex decoder and to the cancellation circuit through the phase detector. The cancellation circuit comprises a wave generator for generating a pair of currents proportional to an amplitude of the pilot signal and a level adjusting circuit for converting one of the currents into the cancelling signal. The other current is converted into the drive signal.
REFERENCES:
patent: 4037165 (1977-07-01), Ogita
patent: 4076963 (1978-02-01), Fujie et al.
patent: 4166925 (1979-09-01), Ienaka
patent: 4300020 (1981-11-01), Toyomaki
Amazawa Kiyoshi
Kuwajima Takeshi
Tanaka Kouichi
Clarion Co. Ltd.
Isen Forester W.
NEC Corporation
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