Research On Reconnaissance Theory And Methods For MIMO Radar Signals

Being part of electronic radar countermeasure,radar reconnaissance refers to detecting,locating,and analyzing the adversary radar.On the one hand,radar reconnaissance gets the intelligence of the opposite radar.On the other hand,it guides our jamming and attack system to make a timely,accurate and effective response.For this purpose,the reconnaissance receiver needs to sense the unknown sources of radiated electro-magnetic energy and extract valuable information from the electromagnetic environment of interest.However,the advent and development of various new radar systems have brought great challenges to radar reconnaissance.Among these new radar systems,multiple-input multiple-output(MIMO)radar is undoubtedly one of the most threat system in military.MIMO radar means the radar systems which benefit from waveform diversity and space diversity of emitted signals.Based on the space distribution of transmitting antennas,MIMO radar can be categorized into co-located MIMO radar and distributed MIMO radar.In this dissertation,related work around the theoretical research,relevant methods,numerical computer simulation and semi-physical off-line experimental verification are carried out on the intercepted signal model,signal detection,modulation parameter estimation and spatial parameter estimation in MIMO radar reconnaissance.The main contents of this dissertation are as follows:1.The transmitting system and waveform characteristics of MIMO radar are analyzed.The reconnaissance signal model for MIMO radar is built.Thus,a joint reconnaissance scheme based on array antennas is proposed to achieve the simultaneous reconnaissance for co-located MIMO radar signal and distributed MIMO radar signal in complex electromagnetic environment.2.The parameters which affect the Signal Noise Ratio(SNR)of intercepted MIMO radar signal in reconnaissance receivers are derived.The similarities and differences between signal detection for MIMO radar and conventional radar are also analyzed.Thus,a signal detection method based on Fractional Autocorrelation and entropy weight processing for noise reduction is proposed to overcome the problem that the detection performance degradation of uncooperative OFDM-LFM signal with the increase number of subcarriers.3.The modulation parameters estimation model of MIMO radar signal is built.Thus,a fast estimation algorithm based on interpolation of Fractional Fourier coefficients is proposed to improve the accuracy of modulation parameters estimation for OFDM-LFM signal in low SNR.Moreover,the estimation error of the proposed algorithm converges asymptotically to Cramer-Rao bound(CRB)with the increase of SNR.4.The array antennas-based Direction of Arrival(DOA)estimation model of distributed MIMO radar signal is built.Thus,a fast-computational spatial Fourier coefficient based DOA estimation method is proposed.This method constructs DOA estimators for multiple overlapped subcarrier signals.Thereby,a clustering algorithm and spatial filtering method are introduced to achieve the separation of distributed MIMO radar signal.5.Most designed OFDM-LFM waveforms are wideband signals in engineering.To solve the direction-finding problem of such wideband signals in low-cost,a SwitchedElement direction-finding system for wideband co-located MIMO radar signal is built.Thus,a DOA estimation method based on instantaneous cross-correlation and lowpass filtering is proposed.Comparing with some existing wideband signal direction finding methods,this method constructs the DOA estimator with only two reception channels.6.The single reconnaissance station based passive localization model for spaceborne MIMO radar is built.Thus,a passive localization method based on compressive sensing framework is proposed.This method integrates the Sparse Bayesian Learning(SBL)algorithm with the preconditions that the estimation for modulation parameters and DOA has already been accomplished to achieve the location of target spaceborne MIMO radar.The effectiveness of the researches above are verified by computer simulation experiment.Then,a semi-physical off-line test platform for MIMO radar signal reconnaissance is built associate with a MIMO radar research group.By analyzing the MIMO radar signal data intercepted with the reconnaissance receiver in the reconnaissance test,the technical feasibility of MIMO radar reconnaissance is verified,and the effectiveness of some signal detection and parameter estimation methods mentioned above are also verified.