Image Number 4 for United States Patent #4910469.
A sampled data FM demodulator samples the FM signal at intervals of (2n.pi.+.pi./2) radians relative to the FM carrier. Pairs of samples S.sub.n and S.sub.n+1 are square and multiplied together to generate sample values S.sub.n.sup.2, S.sub.n+1.sup.2 and S.sub.n S.sub.n+1. These sample values are lowpass filtered in a filter having a cutoff frequency which substantially attentuates at least the second harmonic of the FM carrier. The low pass filtered samples are then combined according to the relation S.sub.n S.sub.n+1 /.sqroot.S.sub.n.sup.2 S.sub.n+1.sup.2 to generate demodulated output samples.