Research On Passive Localization Technology Of New Radar Signals In Complex Environment

Compared with active localization,passive localization does not transmit signals,and presents an analysis and reconnaissance by intercepting the emitter signal.Passive localization plays a more and more important role in electronic countermeasures because of its good concealment,long distance,strong anti-stealth ability and low cost of procurement and maintenance.As the main radiation source object of passive localization system,radar system is constantly optimized and improved.The signal forms,signal processing technology and application scenarios of radar have made great progress in the past few decades.In particular,the emergence of new system radar makes the electromagnetic environment increasingly complex,which brings more and more challenges to passive localization.Distributed multistation passive localization has been studied by scholars due to its advantages of cooperative work among the base stations,fast positioning speed and high precision.As a high-performance localization technology,distributed multistation passive localization technology is closely related to radiation source signal model,interference type,application scenario and other factors.The existing passive localization technology mostly ignores the processing of the waveform information of the emitter,and lacks the targeted research on the passive localization technology of the new radar emitters.Therefore,this paper studies the passive localization technology of new radar signals in complex environment.Theoretical analysis and methodological research on the various radar signals,positioning systems and methods are carried out.The specific work contents are as follows :1.A fast direct position determination(DPD)algorithm based on spectrum detection is proposed to solve the problem of high algorithm complexity and localization performance jump under low signal-to-noise ratio(SNR)in passive localization of single component linear frequency modulation(LFM)signal.The algorithm further derives the objective function of the DPD algorithm,and proposes a decoupled strategy to solve the high-dimensional nonlinear optimization problem in localization.By combining the two-step and one-step localization methods,the proposed fast DPD algorithm achieves joint estimation of the transmitted signal parameters and the emitter position.The simulation results show that compared with the mature positioning algorithms,the proposed algorithm can save more than 90% of the time,and has better and more stable localization performance at low SNR.2.Aiming at the problem of passive localization for multi-component LFM signal emitter,a DPD algorithm based on pseudo Wigner-Ville distribution(PWVD)and spatially variant apodization(SVA)is proposed.The proposed algorithm can cope with the presence of oppressive interference in a complex electronic countermeasure environment,close to a strong radiation source,or in the main lobe of a radiation source transmitting beam,and has better positioning performance.The simulation results show that the signal processed by PWVD-SVA algorithm not only eliminates the cross terms of the multi-component LFM signal,but also reduces the sidelobe level of strong component to nearly-40 d B.Compared with other DPD algorithms for multicomponent signal emitters,the proposed algorithm can improve the accuracy by about200 m when the SNR is-6 d B.3.The problem of passive localization for the MIMO radar signal emitter is studied.Based on the situation that the waveform information transmitted by MIMO radar emitter is completely unknown,and the positioning performance of traditional passive localization algorithms is relatively poor.A DPD algorithm based on KL transform and feature matching technique is proposed.The proposed algorithm can reduce the dimension of signal samples from a large number of signals observed by each base station through KL transform technique,and estimate the signal parameters.Then,the MIMO radar emitter can be found by matching the estimated signal parameter features,so as to effectively utilize the target signal information.The proposed method can improve the signal processing gain,eliminate the influence of noise on the positioning performance as much as possible,and realize the high-precision positioning of MIMO radar signal emitter.The simulation results show that the proposed algorithm can control the root mean square error of localization performance within 50 m when the SNR is 0 d B.4.Aiming at the problem of passive localization of deceptive frequency diverse Array(FDA)radar signals,a passive localization algorithm based on direction modulation(DM)recognition is proposed.By applying the DM technique,the distanceangle coupling of the FDA beampattern can be well eliminated.The algorithm analyzes the reason of deceptive interference caused by FDA emitters to the passive localization system.According to the structural model and beam characteristics of FDA radar,the criterion of FDA beam is given,and two passive location methods are proposed for FDA emitters with different DM modes.For FDA emitters passing through linear DM,according to the decision criterion of FDA beam,the signal parameters such as initial time can be estimated more accurately,and then the cooperative localization algorithm of Chan and Taylor is used to realize the accurate localization of FDA emitters.For the FDA radiation source of nonlinear DM,a localization method based on compressed sensing and subspace algorithm is proposed,which can locate the FDA emitter at less than Nyquist sampling rate.