Digital FSK demodulator

Details Digital FSK demodulator Digital FSK demodulator

1987-03-04

1989-04-25

Griffin, Robert L.

Pulse or digital communications

Repeaters

Testing

375 88, 375 91, 329126, H03K 708, H04L 2714

Patent

active

048254525

ABSTRACT:
The present invention provides a digital frequency shift keying (FSK) demodulator circuit which receives a hard-limited FSK input signal and recovers the modulating baseband signal at 300 baud or less. The FSK demodulator includes a digital phase locked loop demodulator section which receives the FSK input signal and generates a pulse width modulated output the frequency of which is a function of the input signal frequency. The output of the PLL demodulator section is provided to a quantizer which generates a set of parallel numbers. A translating means, for example a code linearizer, converts the parallel numbers into corresponding parallel outputs which are representative of the frequency of the FSK input signal. The parallel outputs are processed by a digital filter which emulates a second-order, low-pass filter. The filter processes the parallel outputs utilizing pulse density modulation. A deglitcher removes noise from the filter output to provide the demodulated data output.

REFERENCES:
patent: 3559083 (1971-01-01), Crouse
patent: 4115738 (1978-09-01), Mitarai et al.
patent: 4485347 (1984-11-01), Hirasawa et al.
patent: 4583239 (1986-04-01), Vance

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