Coherent Demodulation of the Two-Level Amplitude Phase-Shift Keyed Signals: Noise Immunity Issue

There are considered the fast algorithms for the coherent demodulation of the two-level amplitude-phase shift keyed signals (APSK signals) and for the same operation but accompanied by the estimation of the received symbol amplitude via its relative comparison with the preceding symbol amplitude (APSK-RA signals). A great advantage of these algorithms is that they require a minimum number of arithmetic operations per signal period. The phase demodulation is implemented based on the phase detector of multi-level phase keyed signals. The symbol amplitudes are determined by the quadrature channels responses. It is shown that the introduced demodulation algorithms can be implemented in both analog and digital versions. Then one more benefit from the proposed procedure is demonstrated: there is no need for the received signal normalization by its constellation during the APSK-RA signal demodulation implementation. The probabilities of the erroneous demodulation of the received symbol phase and amplitude are estimated. The comparative analysis of the noise immunity of the two-level APSK and APSK-RA signals for the two variants of signal constellations is performed. Statistical simulation of the proposed demodulation algorithms is carried out.