Fast Doppler shift acquisition method for hypersonic vehicle communications

Abstract

Large and rapidly changing Doppler shift poses a huge challenge on fast carrier acquisition for hypersonic vehicle communications. In this study, a novel Doppler shift acquisition method is proposed to increase the acquisition probability and reduce the acquisition time simultaneously. Firstly, the Doppler rate is estimated with a proposed fast blind estimation algorithm. The order of Doppler shift is reduced though twice instantaneous delay autocorrelation operation on the received signal and the modulated information is cancelled, and the Doppler rate can be obtained by the corresponding spectrum analysis. Secondly, the received signal is compensated by the estimated Doppler rate. Finally, the maximum value of the average power spectrum of the compensated result over multiple symbols is detected, and the Doppler shift and Doppler rate can be jointly determined. Furthermore, to improve the acquisition speed, a corrected narrower range, which is determined by the flight conditions of the hypersonic vehicles, is proposed to constrain the search range of the power spectrum peak. Simulation results indicate that, under typical hypersonic flight conditions, the acquisition probability of the Doppler rate increases from 0.52 to 0.86 under − 20 dB. The processing speed can be improved by 75.47% when the length of the combined symbols is 1000.