Passive Radar Detection Algorithm Research Based On Multiple Illuminators

A passive radar is a kind of radar system that employs existing military or civilian illuminating signals in the space environment without transmitting its own signals.The passive radar system consists of surveillance channels and reference channels,where the surveillance channels receive the target return and the reference channels receive the direct signals of the illuminating sources.Passive radar has the ability to detect stealth or low altitude target and it can combat anti-radiation guided missile with low cost and great flexibility and many other advantages.However,the current passive system carries out detecting,locating and tracking based on a single radiation source.The research on combining multiple illuminating sources is less concerned.The passive system can see the target from different perspectives and increase the diversity gain based on multiple radiation sources,avoiding the performance deterioration caused by target glint.In this thesis,we study the following aspects of passive system based on multiple radiation sources:1.When the signals of multiple radiation sources are non-orthogonal,we conduct detection based on a single surveillance channel.Suppose the direct-path signal in the surveillance channel are removed through digital filtering and only noisy target return is remained,we derive two detectors under known and unknown noise power conditions based on generalized likelihood ratio test by estimating unknown parameters.And we give the performance analysis of the detector under known noise power.The simulation results demonstrate the performance superiority and robustness of the signal estimating quality.2.For the direct-path signal in the surveillance channel in realistic case,we study the filtering effect of direct interference based on gradient adaptive lattice filter.The direct signal is learned by reference channel signal and is eliminated at working stage,thus the surveillance signal is utilized to detect target.Simulation results reveal that the filter can obtain a satisfying filtering effect when the number of radiation source is small but may be invalid when the number of illuminators is large.3.Since the filtering is difficult in the case of multiple radiation sources,we propose a novel signal model.When employing multiple surveillance channels and reference channels,we keep the direct-path signal in the surveillance signal model.The unknown signal is estimated by combining both surveillance and reference signals,and the unknown parameters are estimated based on generalized likelihood ratio test.Then the detectors of both known and unknown noise conditions are obtained.We give the theoretical performance analysis of the detector under known noise case.Simulation results show that the proposed detector exhibits a good equivalent filtering performance and robustness,which also demonstrate the effectiveness of idea of regarding the direct signal as strong interference instead of filtering processing.