Method of digital demodulation of a frequency-modulated signal, demodulator and television equipment for implementing this method

摘要

The invention relates to a method of digital demodulation of a frequency-modulated signal, especially a SECAM chrominance signal. In an exemplary embodiment, a demodulator includes: a computing device 1 for determining, for each sample Y(n) of a chrominance signal, a value a1(n) such that: Y(n) = -a1(n).Y(n-1)-a2(n).Y(n-2) + e(n), where Y(n-1) and Y(n-2) are the values of two samples preceding Y(n), where e(n) represents the noise added to the signal, and where a1(n) and a2(n) depend on the instantaneous frequency f(n) of the signal to be demodulated and on the latter's sampling frequency fe; a read-only memory 2 allowing determination of a value f(n) of the instantaneous frequency corresponding to the value a1(n) according to the formula: f(n) = fe DIVIDED 2 pi Arccos (- a1(n) DIVIDED 2 a second computing device 3 for computing a value s(n) of the modulating signal according to the formula: s(n) = f(n) - fo DIVIDED DELTA fo The invention is applicable in particular to SECAM chrominance signal demodulators used in colour television equipment, especially receivers. IMAGE