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A decision feedback-based differential demodulator of double differential phase-shift keying (DDPSK) signals is presented, It is comprised of two consecutively connected differential detectors, which are based on certain reference signals obtained from previously detected data and received signals. Computer simulations demonstrate that the bit error rate performance of the proposed demodulator is comparable to that of the coherent receiver of DDPSK signals.

We extended the decision feedback-based demodulation and equalization techniques for differential phase shift keying (DPSK) to the demodulation and equalization of doubly differential PSK (DDPSK). The decision feedback demodulator for DDPSK comprises two consecutive differential detectors which are based on some reference signals obtained from previously detected and received data. The proposed equalizer is a hybrid of this decision feedback demodulator and a linear feedback equalizer. By modifying the equalizer output based on the decision feedback demodulation before feeding back into its feedback part, the proposed equalizer can act like an equalizer with decision feedback structure. Computer simulation results demonstrate that the performances of the decision feedback demodulation and the equalizer are comparable to those of the coherent receiver and the decision feedback equalizer (DFE) with coherent detection, respectively.

The authors propose to combine linear feedback equalisation and decision feedback demodulation for the equalisation of differentially coherent PSK signalling. By modifying the equaliser output based on the decision feedback demodulation before feeding back, the proposed equaliser can be made to behave like one with a decision feedback structure. Indeed, computer simulation results demonstrate that this equaliser performs much better than existing equalisers, such as linear equalisers for differentially coherent detection. Furthermore its performance is even comparable to that of a decision feedback equaliser with coherent detection.