On the Demodulation of the ADPSK Signals

A digital algorithm for demodulating the amplitude-differential phase shift keyed (ADPSK) signals and its implementation based on a digital phase detector are considered. The transmitted information signal is represented by the known constellation of the APSK signal, in which the multi-level symbol is determined by the amplitude and not by the initial phase, but by the phase shift of the received symbol relative to the previous one. The demodulator is based on digital phase and amplitude detectors, for which an efficient implementation is proposed with the possibility of continuous demodulation of the current phase over an interval exceeding 2π. Coherent signal processing is provided in the absence of phase synchronization of the reference generator and the received signal. The proposed demodulation algorithm is applicable to any type of constellation. The analysis of the signal processing procedure is carried out. The time realizations of the responses of the processing algorithms are considered. The estimates of the noise immunity of the proposed demodulation algorithms are obtained, and their statistical simulation is performed.