Algorithm Estimates Doppler Shift in a Received DPSK Signal

An algorithm estimates the Doppler frequency shift in a received radio signal with square-wave-pulse binary differential-phase-shift-keyed (DPSK) modulation. [With little modification, the algorithm is also extensible to M-ary (where M is an integer > 2) DPSK modulation with pulse shapes other than square.] The algorithm was developed especially for use in processing a received K- or Ka-band signal in a ground mobile receiver in a ground-mobile/satellite communication system. There is a need for estimation of, and compensation for, large Doppler frequency shifts in such a receiver. The algorithm implements a feedforward (open-loop) estimation scheme, providing the needed Doppler estimate prior to detection and subsequent processing (see figure) for extraction of data symbols from the modulation.