| At present,the radar has been incorporated into the communication,navigation,electromagnetic countermeasure(ECM)and other systems,and plays an important role in high-tech information battlefield.A great number of new radar systems are unique,and they are different with the traditional conventional radar system in the radar launch waveform,the number of transceiver antennas,signal processing processes and others.The anti-intercept ability of the new radar system is improved,which has no doubt brought great challenges to the electronic reconnaissance.The military's ability to access information and the joint operations' confrontation methods and means have also been confronted with great changes due to these improvements.Multiple-input multiple-output(MIMO)radar comes into being under these circumstances of huge military demand,and more and more researchers have been attracted by MIMO radar from all over the world.Focused on the problems mentioned above,three kinds of MIMO radar signal models are built with different modulation in this thesis.The relationship between the subcarrier signals and the characteristics of the different transformations are analyzed and summarized.And based on the analysis and summary,MIMO radar signal parameter's estimation and recognition are discussed in the condition of low signal to noise ratio(SNR).The main researches and contributions of this thesis are as below:1.The low SNR characteristic of MIMO radar and the time domain,frequency domain and time-frequency domain characteristics of three commonly used MIMO radar signals are analyzed in the thesis.At the same time,a reconnaissance model for co-located antennas MIMO radar signals and distributed MIMO radar signals is established,which lays the foundation for signal parameter's estimation and recognition.2.The detection performance of the co-located antennas MIMO radar signal and the distributed MIMO radar signal is analyzed by the time domain detection,frequency domain detection and time-frequency domain detection method.Then,a parameter estimation algorithm based on subcarrier merging is proposed for monopulse-multiinput multiple-output(MP-MIMO)radar signal and linear frequency modulation-multiinput multiple-output(LFM-MIMO)radar signal.The method uses the waveform diversity feature of the MIMO radar signal to improve the SNR of the received signal by merging multiple subcarriers.The simulation verifies the effectiveness of the algorithm in the condition of low SNR.3.A signal recognition method based on image processing is proposed for co-located antennas MIMO radar signal.This algorithm utilizes the difference between the cyclic spectrum and the time-frequency spectrum of different modulation types of co-located antennas MIMO radar signal.And using the method of image processing,we suppress the noise and extract the characteristic parameters for signal recognition.The simulation verifies the effectiveness of the algorithm in the condition of low SNR.4.A distributed MIMO radar system recognition method based on information decision is proposed.Based on the relationship within the subcarrier signals of the distributed MIMO radar,this method can make information decisions according to the Emitter Description Word(EDW)of various intercepted radar signals and then recognize the distributed MIMO radar. |
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