Stereo/two-tone demodulator

Details Stereo/two-tone demodulator Stereo/two-tone demodulator

2006-09-05

2006-09-05

Lee, Ping (Department: 2644)

Electrical audio signal processing systems and devices

Binaural and stereophonic

Broadcast or multiplex stereo

C348S485000

Reexamination Certificate

active

07103186

ABSTRACT:
In a stereo/two-tone demodulator for demodulating an intermnediate-frequency signal having stereo or two-tone sound signals modulated on a first and a second sound carrier, the second sound carrier having a lower amplitude than the first sound carrier, ceramic filters or bandpass filters are saved and complete integration can be achieved in that a first (1) and a second (2) linear narrow-band phase-locked loop are provided each having their own frequency selectivity, the first narrow-band phase-locked loop (1) being implemented in such a way that it locks in at the frequency of the first sound carrier, and the second narrow-band phase-locked loop (2) being implemented in such a way that it locks in at the frequency of the second sound carrier. The first narrow-band phase-locked loop (1) is preceded by a first amplifier stage (4) and the second narrow-band phase-locked loop (2) is preceded by a second amplifier stage (5), each amplifier stage controlling the input signal of the subsequent phase-locked loop (1; 2) at a nominal amplitude. A carrier suppression circuit (3) is provided in which an output signal having a phase position of 0° or 180° of a voltage-controlled oscillator (20) of the first narrow-band phase-locked loop (1) and the input signal of the first narrow-band phase-locked loop (1) are superimposed and which supplies a modified interrnediate-frequency signal as an output signal in which the first sound carrier is suppressed and which is coupled to the second amplifier stage (5) preceding the second narrow-band phase-locked loop (2).

REFERENCES:
patent: 4611226 (1986-09-01), Buhse et al.
patent: 4808883 (1989-02-01), Iwaya et al.
patent: 5446411 (1995-08-01), Horsfall et al.
patent: 5537613 (1996-07-01), Matsui
patent: 5654606 (1997-08-01), Weijens et al.
patent: 0254147 (1988-01-01), None
patent: 0643416 (1995-03-01), None

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