APSK blind carrier phase synchronization under low SNR

A blind carrier synchronization scheme based on minimum mean square error (MMSE) phase error detector and digital 2nd order loop is proposed for the demodulation of APSK in a low-SNR environment. In contrast to the existing decision-directed (DD) algorithm, which is widely adopted for blind synchronization, MMSE phase error detector does not involve the hard symbol decision mechanism, thus it is not sensitive to the false judgment of symbol. Obviously, the detection range is broadened and the degree of phase ambiguity is decreased. To reduce the computational overhead of MMSE detector, a look-up table methodology is used in the scheme. Implementation considerations concerning the key parameters of the carrier phase synchronization loop, the sample-rate adaptive strategy and the fixed point design are summarized.