Bs. Song et Is. Lee, A DIGITAL FM DEMODULATOR FOR FM, TV, AND WIRELESS, IEEE transactions on circuits and systems. 2, Analog and digital signal processing, 42(12), 1995, pp. 821-825
An FM demodulator is implemented digitally in software using a quadri-
correlator algorithm so that the FM function can be made compatible wi
th future digital wireless and FM receiver systems. The proposed digit
al FM demodulator uses a sinc(3) decimation filter with its first zero
either on the alternate channels or on the adjacent channels for high
channel selectivity, a digital differentiator using a three-point app
roximation for frequency discrimination, and a digital division for AM
rejection. A bitstream FM signal from a fourth-order bandpass delta-s
igma modulator is FM-demodulated to exhibit a SNDR of 71 dB, a THD of
0.01%, and an AM rejection of 77 dB in simulations using a signal band
limited to 1/200 of the sampling frequency and amplitude-modulated wit
h a modulation index of 0.9 (90% AM).