DSP-based digital FM demodulation for GMSK signals |
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Authors: | B Ramamurthi K Giridhar M A Srinivas |
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Affiliation: | (1) Department of Electrical Engineering, Indian Institute of Technology, 600 036 Madras, India |
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Abstract: | Demodulation of Gaussian Minimum Shift Keying (GMSK) using a limiter-discriminator 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 in hardware, and matched filtering is usually not possible when the Gaussian pulse is wider than a
bit duration. We propose a clock recovery technique based on discrete-time processing of the demodulated baseband signal.
This technique couples very nicely with a new maximum likelihood sequence estimator for the data that uses a whitening filter
followed by a Viterbi decoder. The entire detection algorithm can be implemented in an efficient manner on a Digital Signal
Processor (DSP). Computer simulation results are presented to show that the new algorithm performs better than the conventional
slicer by as much as 5.5 dB. |
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Keywords: | Viterbi decoding digital FM receiver GMSK demodulation |
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