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Optimum receiver structures for phase-multiplexed modulationsA MAP (maximum a posteriori) estimation loop is derived for a QPSK signal and, by suitable approximation to the nonlinearity which arises as a consequence of the MAP theory, is reconfigured with practical realizations that are valid for high and low SNRs. In particular, it is shown that by approximating the hyperbolic tangent nonlinearity in the MAP estimation loop by the first two terms in its power series, an interesting practical realization of this loop results which applies at low SNRs. The error signal in this loop is formed by multiplying the error signal and lock detector output signal of a conventional biphase Costas loop. A generalized linear in-phase channel configuration is proposed which allows carrier reconstruction from an unbalanced QPSK signal at all ratios of data rates and powers in the two channels, even in the limit as these ratios simultaneously approach unity, i.e., balanced quadriphase.
Document ID
19780056980
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Simon, M. K.
(California Institute of Technology, Jet Propulsion Laboratory, Pasadena Calif., United States)
Date Acquired
August 9, 2013
Publication Date
June 1, 1978
Publication Information
Publication: IEEE Transactions on Communications
Volume: COM-26
Subject Category
Communications And Radar
Accession Number
78A40889
Funding Number(s)
CONTRACT_GRANT: NAS9-15240
Distribution Limits
Public
Copyright
Other

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