Electrical audio signal processing systems and devices – Binaural and stereophonic – Broadcast or multiplex stereo
Patent
1985-01-16
1987-12-29
Isen, Forester W.
Electrical audio signal processing systems and devices
Binaural and stereophonic
Broadcast or multiplex stereo
381 16, H04H 500
Patent
active
047165901
ABSTRACT:
This invention discloses an AM stereo transmission method characterized in that when left and right audio signals L and R are transmitted as an AM stereo signal which is represented by S=A cos(.omega.t+.phi.) wherein A denotes an amplitude, .omega. a carrier angular frequency and .phi. a phase angle given by tan.sup.-1 (L-R)/1+L+R, the audio signal of low frequency is transmitted at an amplitude A=(1+L+R), and the audio signal of high frequency is transmitted at an amplitude A=.sqroot.(1+L+R).sup.2 +(L-R).sup.2. The modulator according to the present invention comprises a matrix circuit for providing signals (L+R) and (L-R), an orthogonal modulator to produce an AM stereo signal .sqroot.(1+L+R).sup.2 +(L-R).sup.2 cos(.omega.t+.phi., an amplitude controller, an amplitude control signal generator circuit and a low-pass filter. In the modulator the said AM stereo signal S is changed to the signal (1+L+R)cos(.omega.t+.phi.) for audio signal of low frequency by controlling the amplitude controller. The demodulator according to the present invention comprises an amplitude controller to which the AM signal S=A cos(.omega.t+.phi.) is inputted, an orthogonal demodulator, an matrix circuit for driving signals L and R from signals (L+R) and (L-R) obtained by the orthogonal demodulator, an amplitude control signal generator circuit and a low-pass filter. In the demodulator the said AM stereo signal S=(1+L+R)cos(.omega.t+.phi.) for audio signal of low frequency is changed to the signal .sqroot.(1+L+R).sup.2 +(L-R).sup.2 cos(.omega.t+.phi.) by controlling the amplitude controller.
REFERENCES:
patent: 4172966 (1979-10-01), Parker et al.
patent: 4192968 (1980-03-01), Hilbert et al.
patent: 4406922 (1983-09-01), Parker et al.
patent: 4489431 (1984-12-01), Ecklund
Iida Hiroshi
Takahashi Susumu
Isen Forester W.
Sansui Electric Co. Ltd.
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