Demodulation of D/sup 2/PSK with a DPSK detector and improved error performance in AWGN

Proposed in this paper is a new demodulation scheme for a double differential PSK (D/sup 2/PSK) signal. It consists of a first-order differential detector (i.e. a conventional DPSK detector) with an adaptive decision-feedback rotation part followed by a differential decoder. A decision is made on the first-order phase difference (FOPD) rather than the second-order phase difference (SOPD), and the information-carrying SOPD is recovered by differentially decoding of the decided FOPDs. As a result the effect of the AWGN is significantly reduced; hence the error performance improves. Analysis shows that the symbol error rate of D/sup 2/PSK with such a receiver is approximately twice as high as that of DPSK, which has been verified by the simulation for quaternary (M=4) D/sup 2/PSK.