A Novel Method for DFO Estimation of Radar Signals with DTO/DFO Ambiguity in GEO-LEO Dual-Satellite Geolocation System

In a GEO-LEO dual-satellite geolocation system, the estimations of the differential time offset (DTO) and differential frequency offset (DFO) are ambiguous at the same time. Aiming at this problem, the ambiguity of the coherent pulse trains signal is analyzed. And, the sequence of the differential time of arrival (TOA) is obtained by the roughly paired pulse trains to avoid the difficulty of the pulse match with high-density in the time domain. The coarse DFO whose ambiguity is eliminated is estimated by the central difference of DTO, and the performance of the coarse DFO estimation is derived. The result shows that the estimation error increases with the increasing of the carrier frequency of the emitter, the increasing of the error of the TOA and the decreasing of the time interval of the differential DTO. The numerical simulations have demonstrated that the coarse DFO estimation error is consistent with the theoretical value, and the estimation accuracy of the DFO approximates the Cramer-Rao lower bound (CRLB) when the coarse DFO estimation without ambiguity is obtained by setting the appropriate differential interval. The new approach is convenient for engineering implementation, and could provide good references for DFO estimation of the radar signal in a long base line location system. © 2019, Editorial Dept. of JA. All right reserved.