This article contains analyses of the performance of various carrier synchronization

loops for offset quadrature phase-shift-keying (OQPSK) modulation, all

motivated in one form or another by the maximum a posteriori (MAP) estimation

of carrier phase. When they are implemented as either high or low signal-to-noise

ratio (SNR) approximations to the generic implementation suggested by the MAP

estimation of carrier phase for an OQPSK signal, it is shown that the loops behave

more like biphase than quadriphase loops in that they only exhibit a 180-deg phase

ambiguity rather than the 90-deg phase ambiguity typical of the latter.