| When detecting remote moving targets,airborne bistatic radar can expand the detection range by the forward advantage of the receiver's position,and has a longer target detection distance than monostatic radar.However,the bistatic radar configuration makes clutter data more complex and presents nonstationary and nonhomogeneous characteristics,thus making target detection more difficult.Aiming at this problem,this paper mainly studies the target detection of airborne bistatic radar under complex clutter.The research content is divided into the following two aspects:Moving target detection based on power spectrum uses the separation of target and clutter scattering point in space-time two-dimensional plane to judge whether there is a target by measuring the distance between clutter ridge and detection point.However,in the case of bistatic,it is difficult to measure the relationship between detection point and clutter ridge directly due to the complex nonhomogeneous nonlinear characteristics of clutter ridge.To solve this problem,this paper proposes a method of mapping bistatic radar clutter into a virtual linear clutter ridge by transformation matrix,and then detecting the target by using the distance relationship between the virtual linear clutter ridge and the detection point in two dimensions of space and time.The method firstly uses space-time interpolation method to convert bistatic radar clutter into virtual linear clutter ridge,and then fits the equation of virtual clutter ridge through the transformed data.Threshold detection is carried out on the power spectrum of the transformed data,noise is filtered out,the target and clutter are retained as detection points,the distance from the detection point to the virtual clutter ridge equation is calculated,and the target and clutter can be distinguished according to the size of the distance,so as to achieve the purpose of target detection.Under the bistatic MIMO radar system,the gain-phase errors of the receiving and transmitting arrays,the nonhomogeneous of training samples or the insufficient number of training samples will weaken the effect of space-time adaptive processing.To solve the problem of gain-phase errors,this paper proposes an algorithm to correct the gain-phase errors of MIMO radar transmission and reception by using the projection matrix of the orthogonal complementary space to the clutter subspace.Firstly,the projection matrix of the orthogonal complementary space to the clutter subspace is calculated by using all the clutter scattering steering guidance vectors in one range bin,and then the correction matrix of the gain-phase errors is calculated by using this projection matrix.Aiming at the problems of nonhomogeneous of clutter and insufficient number of samples,this paper proposes a clutter pre-filtering algorithm based on projection matrix.Firstly,the projection matrix is used to filter out most of the clutter data,and then the remaining clutter data is processed using traditional space-time adaptive processing algorithm.Simulation results show that the performance of the proposed method is better than the existing bistatic MIMO radar clutter suppression methods.. |
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