A performance analysis of coherently demodulated PSK using a digital phase estimate in frequency hopped systems

Most existing frequency hopping AJ systems utilize a non-coherent waveform such as differential phase shift keying (DPSK) or frequency shift keying (FSK). This choice is based on a trade-off between the efficiency of the waveform and the difficulties entailed in reestablishing a phase reference at the beginning of every hop. An alternative technique that is being explored for several planned systems is the use of reference symbols combined with coherent demodulation. If several reference symbols of known phase are sent during each hop then the receiver can establish the absolute carrier phase and perform coherent demodulation. This paper explores the performance of frequency hopped systems utilizing reference symbols with a PSK waveform in both a benign and stressed environment. The results indicate that if as few as 10 reference symbols/hop are used that near coherent performance is obtained. Furthermore, the use of reference symbols yielded performance better than that obtained by differential encoding and non-coherent detection for all cases considered