A novel algorithm for frequency de-hopping in radars using agile bandpass sampling for electonic support measurement

Modern radars use frequency hopping as an effective anti-jamming technique by changing their frequencies from pulse-to-pulse and thus making their blind estimation a challenging task for Electronic Warfare (EW) receivers. In this paper, a novel frequency de-hopping algorithm is proposed using agile band pass sampling by directly sampling the intercepted RF signal using three selected sampling frequencies. Under-sampling creates image frequencies around the radar carrier at integral multiples of the sampling frequencies. The proposed algorithm exploits this effect by searching for the unique/common frequency among three frequency image vectors using iterative mathematical modeling. It is shown that the proposed algorithm achieves comparably better estimation performance to the already existing single sampling chain heterodyne receivers at advantage of direct RF sampling using low speed ADCs. The achieved estimation performance is closer to CRLB. The effectiveness of frequency resolution and noise tolerance level, selection criteria of sampling frequencies, estimation time complexity of de-hopping and operational SNR range of the proposed algorithm are discussed to elaborate its strengths and limitations in EW applications.