Research On Direct Positioning Method Of The Satellite Signal Based Passive Radar

The satellite signals of the Global Navigation Satellite System(GNSS)are used as opportunity illuminators to form a Passive Multiple Input Multiple Output Radar System(PMR)with multiple ground receivers.The multi-channel receiver is used to receive and separate all the target scatter signals of visible satellite signals in the field of view.Considering the MIMO signal processing system,the orthogonality between the GNSS satellite signals is fully explored to make it feasible to effectively improve the target detection performance and positioning accuracy.In this paper,the mathematical model of the passive MIMO radar network is firstly established based on the signal characteristics of GNSS.The feasibility of the system is verified by mathematical derivation and simulation.Secondly,the solution framework is proposed to complete the multipath signal separation.Signal recovery in reference channel and interference suppression in echo channel which are common problems in the target detection and localization in passive radar.Step one is separating the direct signal and the target signal into the reference channel and the echo channel by combining the technology of orientation and beamforming.Then blind equalization is utilized to suppress the multipath interference signal in the reference channel,and the adaptive filtering is used to suppress direct signal interference in the echo channel.For multipath interference with non-zero Doppler shift,a Multi-Channel Normalized Least Mean Square(MCNLMS)algorithm is proposed.The numerical simulations of the classical LMS algorithm,NLMS algorithm,RLS algorithm and the proposed MCNLMS algorithm demonstrate the effectiveness of multipath interference suppression.Finally,the target detection and localization in passive MIMO radar are discussed.Based on the generalized likelihood ratio,the RS-GLRT detector based on the correlation between reference channel and echo channel,and the SS-GLRT detector based on the correlation of echo channel are derived.The performance of GLRT-based detectors is compared with C-CAF detector and AC-CAF detector based on cross-ambiguity function.Moreover,the relation of detection probability,direct signal to noise ratio(DNR),target signal to noise ratio(SNR)and signal length L is discussed.Since the detection function value is the largest when the position state quantity in the detector is an estimation of the position of the target signal,the estimated position of the target signal can be found by the spectrum peak search.The PMR-GLRT algorithm and the PMR-CAF algorithm are proposed to direct position determination.Considered the estimated satellite signal parameters,the RS-GLRT algorithm,C-CAF algorithm and AC-CAF algorithm shows good localization performance for both stationary and moving targets in the numerical simulations.