A practical comparison of PSK demodulation techniques

Demodulation techniques for multilevel phase shift keying (MPSK) are compared on the basis of theoretical performance and complexity of implementation. The techniques employed for binary PSK (BPSK) are extended to the general MPSK case, with emphasis on the problem of extracting carrier synchronization from the BPSK signal. Three types of synchronization techniques are considered: the squaring loop, the Costas loop, and the decision-directed loop. It is shown that decision-directed demodulators are practical and cost-effective implementations for many applications.