Doppler-shift correction via correlation for a received QPSK signal

The authors consider a novel technique for the measurement and correction of the Doppler shift (frequency offset) in a received QPSK signal, where the Doppler shift may be very high, the signal/noise ratio very low, and the receiver has no prior knowledge of the received data symbols. The technique is designed for synchronous data and is to operate prior to the instigation of a phase locking algorithm necessary for coherent demodulation. It reduces the Doppler shift to a value within the capture range of the phase correction loop, and does not operate during the phase acquisition period nor during data detection. The authors first describe various arrangements of the new Doppler-shift corrector, together with the original DFT Doppler-shift corrector, and they then present the results of computer-simulation tests to assess the performances of the different systems.<>