Electrical audio signal processing systems and devices – Binaural and stereophonic – Broadcast or multiplex stereo
Reexamination Certificate
2006-11-07
2006-11-07
Chin, Vivian (Department: 2615)
Electrical audio signal processing systems and devices
Binaural and stereophonic
Broadcast or multiplex stereo
C455S239100
Reexamination Certificate
active
07133527
ABSTRACT:
An arrangement for decoding a stereo multiplex signal, comprising a baseband sum signal (L+R), a difference signal (L−R) which is amplitude-modulated on a suppressed sub-carrier and a pilot signal having a frequency located between the frequency bands of said sum and difference signals, said arrangement having an input for the stereo multiplex signal coupled through parallel stereo sum and difference signal paths to first and second inputs of a dematrix circuit, a synchronous demodulator being included in the difference signal path, a local sinusoidal sub-carrier being supplied to a carrier input of said synchronous demodulator for a synchronous demodulation of said amplitude-modulated difference signal (L−R) into baseband. To maximize stereo channel separation the arrangement is provided with an automatic gain control loop comprising a first mixer stage receiving a reference signal, a signal output thereof being coupled to a second mixer stage, both mixer stages having carrier inputs being supplied with said local sinusoidal sub-carrier for a respective up and down conversion of said reference signal, a signal output of said second mixer stage being coupled through a 6 dB attenuator to a difference circuit providing the difference between the output signal of the attenuator and the reference signal, said difference circuit being coupled to a control input of gain controlled amplifying means for varying the gain of said synchronous demodulator and said first and second mixer stages.
REFERENCES:
patent: 4032717 (1977-06-01), Mallon
patent: 4221928 (1980-09-01), Franssen et al.
patent: 5257312 (1993-10-01), Therssen et al.
patent: 5440586 (1995-08-01), Den Braber
patent: 6226504 (2001-05-01), Takagi
Chin Vivian
Lao Lun-See
McDermott, Esq. Robert M.
Semiconductor Ideas to Market B.V.
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