Compensating frequency drift in DPSK systems via baseband signal processing

A new baseband signal processing method for compensating frequency shift in DPSK systems is introduced. This method consists of a signal processor for initial acquisition of the frequency shift and a simple adaptive equalizer for tracking. The former is based on the observation that the effect of the frequency shift can be eliminated by using boundary values of the received baseband signal between symbol periods. The latter is a single tap equalizer employing the least mean square (LMS) adaptation algorithm. Computer simulation results demonstrate that the proposed frequency shift compensation technique outperforms existing methods and works well for a wide range of frequency shifts.