Electrical audio signal processing systems and devices – Binaural and stereophonic – Broadcast or multiplex stereo
Patent
1990-03-21
1991-05-07
Ng, Jin F.
Electrical audio signal processing systems and devices
Binaural and stereophonic
Broadcast or multiplex stereo
381 7, 329304, 329305, 329306, H04H 500
Patent
active
050143166
ABSTRACT:
An audio detector circuit forms L+R and L-R audio signals from an intermediate frequency compatible quadrature amplitude modulated signal in the form (1+L+R)cos(fct+.phi.) where .phi. contains phase modulated L+R and L-R signals. An envelope detector generates an L+R audio signal and in-phase and quadrature phase detectors produce L+R and L-R audio signals, respectively. The difference between L+R outputs of the envelope and in-phase detectors are amplified to generate a cosine correction signal. Each detector includes a differential operational amplifier having an field effect feedback transistor coupled between each amplifier output and the corresponding input and an field effect transistor coupling the compatible quadrature amplitude modulated signal to the operational amplifier inputs. The impedances presented by the feedback transistor are varied by the cosine correction signal to remove the cosine component of the compatible quadrature amplitude modulated signal while frequency multiplication at the IF frequency rate provides the correct phase audio signal for matrix and noise processing.
REFERENCES:
patent: 4371747 (1983-02-01), Hilbert
patent: 4716590 (1987-12-01), Takahashi et al.
patent: 4845750 (1989-07-01), Ecklund et al.
Kennedy Richard A.
Manlove Gregory J.
Marrah Jeffrey J.
Chen Sylvia
Delco Electronics Corporation
Duke Albert F.
Ng Jin F.
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