Double differential PSK scheme in the presence of Doppler shift

A double differentially coherent demodulation scheme (DDPSK) is proposed for digitally phase modulated signals: its performance is theoretically independent on slow carrier frequency fluctuations and this result is obtained by means of a very simple and reliable structure. The theoretical analysis of the ideal DDPSK shows that, in the absence of carrier frequency shift, it suffers a penalty of about 4 dB with respect to the conventional DCPSK demodulation scheme. Since the potential applications of such a demodulation scheme are in the field of the air-to-air or air-to-ground data links, a comparative analysis was made with respect to the conventional DCPSK in the presence of a carrier frequency shift, and the conditions are derived (in terms of carrier frequency, relative speed and information rate) under which the DDPSK performs better.