Robust Doppler ambiguity resolution using multiple paired pulse repetition frequencies

In the present study, a robust algorithm for Doppler ambiguity resolution is proposed. This new algorithm is based on a recently developed robust phase unwrapping (RPUW) algorithm and the Ferrari-Be-renguer-Alengrin (FBA) method using multiple pulse repetition frequencies (PRF). In the FBA method, the PRFs are grouped into pairs and each paired PRF values are symmetric about 1. Then the Doppler frequency estimation is divided into two steps (folded frequency, i.e. the fractional part and ambiguity order, i.e. the integer part): the folded frequency is estimated by circularly averaging the folded frequency estimates for each pair PRF and the ambiguity order is obtained by searching the finite integers based on a quasi-maximum-likelihood criterion using the estimated folded frequency. By observing that the folded frequency estimates for each pair PRF may have errors because of the finite FFT implementations, noise and interference, the circular mean of the erroneous folded frequency estimates may be erroneous too, which may lead to an erroneous ambiguity order estimate, that is, a large error. In this study, the authors replace the integer ambiguity order searching by a recently developed RPUW algorithm that is robust to the frequency estimates from the FFT implementations. The simulation results of this study show that the newly proposed algorithm significantly outperforms the FBA method and is also better than the RPUW algorithm.