Research On Singal Processing And Simulation Of Vitrual Aperture MIMO-OTH Radar

In recent years,Multiple Input Multiple Output Over the Horizon(MIMO-OTH)radar has become an important research area of the new system sky wave radar.Based on the construction of a virtual array MIMO-OTH radar system,this thesis mainly studies the characteristics of the virtual array MIMO-OTH radar,sea clutter suppression and slow target detection,and ionospheric phase pollution correction.In this thesis,the main work and contributions are as follows:(1)Construction of virtual array MIMO-OTH radar systemIn this thesis,an ionospheric model and a ray propagation path model are given.Based on these,a virtual array MIMO-OTH radar system is constructed,and its signal processing flow is derived,including matched filtering,beamforming,doppler processing,and target detection.Etc.Finally,the validity of the system construction was verified by simulation.(2)Analysis of MIMO-OTH radar virtual arrayThe sparse array method brings a larger effective aperture to the MIMO-OTH radar.This thesis analyzes the principle that MIMO radar can form virtual array elements,and discusses two types of signal processing methods: full virtual array element and effective virtual array element,the latter has a lower beamforming dimension.Finally,this thesis discusses the performance differences between the virtual array MIMO radar and the traditional phased array radar in terms of output signal-to-noise ratio,angular resolution,and angular error.(3)Sea clutter suppression and slow target detectionAiming at the problem of sea clutter concealing the slow target at sea,this thesis studies the sea clutter cycle cancellation algorithm,and finds that the cycle cancellation algorithm has a significant suppression effect on the Bragg peak.This thesis also presents the eigenvalue decomposition method based on neighbouring range cells.This algorithm uses the clutter correlation between current range cells and neighbouring range cells to construct a covariance matrix,and filters out clutter signals through eigenvalue decomposition.Simulation results show that the algorithm not only applies to Bragg peaks,but also to the second-order spectrum.In addition,this thesis also gives a clutter suppression method based on the MVDR algorithm,which aims at minimizing clutter noise power,and it accurately estimates the Doppler frequency of the target signal.(4)Ionospheric distortion correctionAiming at the ionospheric phase pollution problem,this thesis deeply researches the decontamination algorithm based on the cubic polynomial phase,and finds that the algorithm's estimated polynomial coefficient error is coupled.Because of this,a new polynomial phase decontamination method is proposed.The algorithm is modeled with a fifth-degree polynomial phase,and a fast decoupling polynomial coefficient calculation method is given.The simulation results show that when the phase pollution changes slowly,both algorithms can well correct the phase pollution.When the phase pollution changes rapidly,there are more burrs on the clutter spectrum after the cubic polynomial algorithm decontaminates,and the proposed algorithm can still maintain a good performance of decontaminating the phase.