Demodulators – Amplitude modulation demodulator – Having specific distortion – noise or other interference...
Patent
1984-08-27
1985-11-19
Grimm, Siegfried H.
Demodulators
Amplitude modulation demodulator
Having specific distortion, noise or other interference...
329110, 375 80, 375 88, 375 89, H04L 2714
Patent
active
045545090
ABSTRACT:
A demodulator for continuous phase frequency shift keyed signals is implemented through the medium of computer software and processes incoming signals which are initially passed through an interference reduction filter. The disclosed demodulation algorithm makes use of the fact that the phase is continuous between adjacent symbols, as well as other symbol to symbol correlations, to reduce the error rate by processing a string of symbols utilizing a two step symbol decision process, instead of merely demodulating a symbol from a time slice of the received signal. The two step symbol decision process consists of a forward and reverse pass, wherein a candidate symbol predecessor is recursively chosen for each symbol, according to a maximum likelihood decision criterion, on the forward pass. Once a singular candidate predecessor is encountered, a reverse pass is initiated, so that a unique sequence of symbols is chosen back to a previously encountered singular predecessor.
REFERENCES:
patent: 4027266 (1977-05-01), Clark
patent: 4096442 (1978-06-01), McRae et al.
patent: 4291275 (1981-09-01), Nossen
patent: 4335354 (1982-06-01), Crandall et al.
Bell Edward L.
Davis David L.
Grimm Siegfried H.
HRB-Singer, Inc.
Smith Robert E.
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