Pulse or digital communications – Repeaters – Testing
Patent
1988-06-07
1991-04-09
Safourek, Benedict V.
Pulse or digital communications
Repeaters
Testing
375 56, 375 85, 375 97, H04B 110
Patent
active
050070681
ABSTRACT:
Doppler in a communication system operating with a multiple differential phase-shift-keyed format ("MDPSK") creates an adverse phase shift in an incoming signal. An open loop frequency estimation is derived from a Doppler-contaminated incoming signal. Based upon the recognition that, whereas the change in phase of the received signal over a full symbol contains both the differentially encoded data and the Doppler induced phase shift, the same change in phase over half a symbol (within a given symbol interval) contains only the doppler induced phase shift, and the Doppler effect can be estimated and removed from the incoming signal. Doppler correction occurs prior to the receiver's final output of decoded data. A multiphase system can operate with two samplings per symbol interval at no penalty in signal-to-noise ratio provided that an ideal low pass pre-detection filter is employed, and two samples, at 1/4 and 3/4 of the symbol interval T.sub.s, are taken and summed together prior to incoming signal data detection.
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Divsalar Dariush
Simon Marvin K.
Adams Harold W.
Chin Stephen
Jones Thomas H.
Manning John R.
Safourek Benedict V.
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