Demodulators – Amplitude modulation demodulator – Having specific distortion – noise or other interference...
Patent
1981-08-17
1984-11-27
Miller, Stanley D.
Demodulators
Amplitude modulation demodulator
Having specific distortion, noise or other interference...
329122, 375 82, 375 88, H03D 318, H04L 2714
Patent
active
044853475
ABSTRACT:
The disclosed FSK demodulator includes a digital PLL for converting an FSK modulated input signal with two different frequencies to rectangular waveforms having durations as determined by those frequencies, two reversible N bit counters for counting clock pulses to determine instantaneous duty factors in the form of N parallel bits of the waveforms for each pulse repetition period, and a read only memory for multiplying alternate outputs, except for the sign bit, from the counters by a ratio of the lower to the higher frequency of the input signal. Then, a digital first-order low-pass filter removes a high frequency component from the output of the read only memory, resulting in a demodulated binary signal. The binary signal may be produced by setting or resetting a FLIP-FLOP when the sign bit from each of the counters is respectively a binary ONE or ZERO. Alternatively, another reversible M bit counter (when M>N) may count the clock pulses to equal the output from the read only memory.
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patent: 4190802 (1980-02-01), Levine
patent: 4345211 (1982-08-01), Longworth
Grzegorek, Z. et al., "Digital FSK Receiver has Small Delay", Electronic Engineering, v. 49, N. 592, May 77, p. 25.
R. J. McAulay, "The Effect of Staggered PRF's on MTI Signal Detection", IEEE Transactions on Aerospace and Electronic Systems, Jul. 1973, pp. S15-S18.
G. Pasternack et al., "Analysis and Synthesis of a D-PLL for FM Demodulation", Bell System Technical Journal, Dec. 1968, pp. 2207-2237 (missing pp. 2222 and 2223).
Hirasawa Shigeichi
Horiguchi Akira
Miller Stanley D.
Mitsubishi Denki & Kabushiki Kaisha
Paxman W. R.
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