Patent ID: 7295631

Claim:
A stereo demultiplexer receiving a stereo multiplex signal which comprises at least a modulated difference signal and a pilot carrier signal, the demultiplexer comprising: a first complex mixer to downconvert a helper signal which equals to the modulated difference signal, to a not synchronized complex baseband signal on basis of a fixed frequency; a complex sampling rate decimation unit receiving the not synchronized complex baseband signal and sampling rate decimating said complex baseband signal with a factor N where N is a real number; and a second complex mixer synchronizing and coherent demodulating the sampling rate decimated not synchronized complex baseband signal on basis of a first complex carrier signal derived on basis of the pilot carrier signal and the fixed frequency, wherein a DPLL receiving the pilot carrier signal and generating a first complex helper carrier signal that is locked to the second harmonic of the pilot carrier signal, and a third complex mixer to generate the first complex carrier signal receiving the first complex helper carrier signal and mixing it with a second complex helper carrier signal according to the fixed frequency and a correcting phase offset so that the synchronized complex baseband signal comprises, in its in phase component, the in phase component of the synchronized helper signal, and in its in quadrature component, the in quadrature component of the synchronized helper signal.