Importance

Loading Importance Indicators...

Abstract

This invention provides a method and apparatus for processing a received digitally-modulated carrier signal to coherently demodulate or, for some applications, coherently demodulate and decode said signal when the signal's phase has an undesired component and/or to generate successive estimated values of said undesired phase of the received signal. Signal processing operations are performed in accord with a composite trellis diagram formed from one or more component trellis diagrams that are phase-displaced versions of a root trellis diagram and, when applicable, phase migration transitions. Desired variations in signal parameter values that result from modulating the signal effect transitions between states in the root trellis diagram. For some embodiments of this invention, phase migration transitions which typically recur periodically in the composite trellis diagram accommodate undesired variations in the received signal's phase for which the rate of change in phase is adequately small relative to the modulation rate but not otherwise restricted. The applicable signal processing is implemented through appropriate application of the Viterbi maximum likelihood processing algorithm or any variant, derivative or counterpart thereof. A demodulated data sequence and/or a sequence of estimated values of the received signal's phase are derived from appropriately structured path history values generated for the multiple states in the composite trellis diagram. The received signal processed may have a continuous envelope or may be comprised of a succession of non-overlapping signal bursts which originate at one or more transmit locations, e.g., as in a TDMA system.

Loading the Abstract Image...

First Claim