DSP-BASED DIGITAL FM DEMODULATION FOR GMSK SIGNALS

Demodulation of Gaussian Minimum Shift Keying (GMSK) using a limiter-d iscriminator is a low complexity alternative to coherent demodulation. This so-called digital FM demodulation is followed by clock recovery, sampling, and thresholding.; Conventionally, clock recovery is done i n hardware, and matched filtering is usually not possible when the Gau ssian pulse is wider than a bit duration. We propose a clock recovery technique based on discrete-time processing of the demodulated baseban d signal. This technique couples very nicely with a new maximum likeli hood sequence estimator for the data that uses a whitening filter foll owed by a Viterbi decoder. The entire detection algorithm can be imple mented in an efficient manner on a Digital Signal Processor (DSP). Com puter simulation results are presented to show that the new algorithm performs better than the conventional slicer by as much as 5.5 dB.