PRI Characteristics Analysis under Complex Environment of Spurious and Missing observations

In ESM receivers, Pulse Repetition Interval (PRI) estimation is an important part of emitter identification and tracking. Under poor SNR conditions, some of the received pulses are less likely to be detected causing a significant error in PRI type and period estimation. The same effect is observed if the receiver detects the multipath reflection based spurious pulses inducing false PRIs. This paper proposes a novel algorithm for diagnosing the presence of missing or false periods in estimated PRI stream. The proposed algorithm calibrates the PRI modulation detection thresholds and re-aligns the estimated PRI vector by removal of the missing/spurious periods. The algorithm is evaluated against different input configurations of fixed, staggered, slide and jittered PRIs. It is investigated through simulations that the PRI modulation type is highly effected by incorporation of false PRIs. The estimation performance of the proposed algorithm is evaluated by Monte-Carlo iterations. It is concluded through simulations that if the PRI estimation thresholds are calibrated for detection and removal of the missing/spurious pulses, the estimation inaccuracies can effectively be compensated.