Patent ID: 7103186

Claim:
A stereo/two-tone demodulator for demodulating an intermediate-frequency signal comprising 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, characterized in that the demodulator comprises: a first and a second linear narrow-band phase-locked loop each having a respective frequency selectivity, the first narrow-band phase-locked loop being implemented for locking in at a frequency of the first sound carrier, and the second narrow-band phase-locked loop being implemented for locking in at a frequency of the second sound carriers; a first amplifier stage coupled to an input of the first narrow-band phase-locked loop, and a second amplifier stare coupled to an input of the second narrow-band phase-locked loop, each of said first and second amplifier stages controlling the input signal of the subsequent respective narrow-band phase-locked loop at a nominal amplitude; and a carrier suppression circuit coupled to receive an output signal having a phase position of 0° or 180° of a voltage-controlled oscillator of the first narrow-band phase-locked loop, and the input signal of the first narrow-band phase-locked loop, said carrier suppression circuit superimposing said output signal and said input signal for supplying a modified intermediate-frequency signal as an output signal in which the first sound carrier is suppressed, the output signal from said carrier suppression circuit being coupled to the second amplifier stage preceding the second narrow-band phase-locked loop.