Research On Performance Evaluation And Optimization Of Broadband Cognitive Passive Radar

Passive radar itself does not emit electromagnetic waves,it has four anti(antiinterference,anti-air defense,anti-radiation missile,anti-stealth)ability and with the advantages of low cost.The introduction of cognition can improve the ability of the system to adapt to the environment.However,because of the absence of transmitters and the uncontrolled waveform,cognitive methods based on “recognition-evaluationpreference” bring new challenges.In this paper,the parameter estimation performance of multi-carrier signals working as passive radar illumination sources are evaluated.Under the assumption of line of sight and point target,the CRB of the monostatic non-coherent radar system for multi-carrier signals are derived,we compare the results between FBMC,a kind of non-orthogonal multi-carrier modulated signal and OFDM's,which is a typical orthogonal multi-carrier modulated signal,about CRB of parameter estimation.The simulation results indicate that FBMC has advantages over OFDM as the illumination source for passive radar.After removing the above assumptions,the CRB closed-form solution of broadband multi-carrier signal is derived,the bandwidth of the wideband signal is larger than the coherent bandwidth of the channel,resulting in multipath effect,and the RAKE receiver is used to superimpose the different diameter signals to improve the detection performance.Next,ambiguity function for MIMO radar system based on the SCMA are analyzed in detail.Woodward ambiguity function and MIMO ambiguity function are adopted for SCMA and CDMA signals.The simulation result shows that non-orthogonal waveforms can provide better Doppler resolution and the passive radar where MIMO technology is introduced can have performance improvement,all of which will give efficient instructions to the design of passive radar systems.Then,a passive radar system based on LTE is develped,and indoor moving target detection is realized.LTE downlink signal is firstly generated as the passive radar illuminaton source in labview.Then the least squares adaptive FIR direct wave interference cancellation algorithm,and the delay range-Doppler mathed filter 2D moving target detection algorithm are realized.Lastly,DOA estimation of L array based on propagator is paroposed.Based on a cross-correlation matrix formed from the L-shaped array,the proposed algorithm obtains the automatic pairing elevation and azimuth angles without eigen-decomposition,which can avoid high computational cost.Besides,the cross-correlation matrix eliminates the effect of noise,which can achieve better DOA performance.Simulation results demonstrate that,the algorithm achieves a good compromise between complexity and estimated performance.At low SNR and with small number of snapshots,it also has slightly inferior DOA performance but with significantly lower complexity.