Research On Energy Focusing And Detection Technology Of Range Migrating Radar Target

Extending the time of coherent integration is an effective means to improve the detection capability of radar to detect weak targets.However,under the condition of long-time observation,when the target moves at a high speed or the radar range resolution is high,the target tends to cross several range units,which is called range migration.There are mainly two categories of range migration targets: a)high-flying fighter planes and hypersonic vehicles;b)low-flying cluster drones.The range migration in the former is due to the highspeed movement of the target,while the latter is mainly due to the high resolution of the radar.The common characteristic of the two kinds of targets is that the echo energy is dispersed in several adjacent range units,but the difference is that they have completely different motion characteristics and detection background,which cannot be described by the same model.Based on the different motion characteristics and detection background of two kinds of targets,this dissertation studies the detection problem of range moving targets.The main work is summarized as follows:1.The effects of target attitude,size and radar carrier frequency on echo correlation are studied and two fast implementation methods of motion parameter estimation are designed.With the target being modeled as a cone model,the correlation coefficient expression of target echo at different time is derived.The influence of target attitude,size and radar carrier frequency on echo correlation is analyzed,which lays a foundation for the follow-up research.First-order improved auto correlation function(IAF)and second-order IAF are defined,so that the echo autocorrelation operation,which is used in scaled inverse Fourier transform(SCIFT)and second-order Wigner-Ville distribution(So WVD)algorithms,can be realized by FFT.This method greatly reduces the computation complexity and improves the real-time performance of the two algorithms.It is theoretically proved that the proposed algorithm can perform the function of the original algorithm without any performance loss.2.The distortion-free condition of matching filter when the scale of radar echo appears is derived and a hypersonic vehicle detection algorithm is proposed based on this condition.The influence of timewidth-bandwidth-product and target velocity on matched filter is analyzed quantitatively,the distortion free condition of matched filter is derived,and the parameter search step size of generalized matched filter parameter is determined.The parameter search of generalized matched filter is combined with the fuzzy number search in Keystone transformation(KT)to overcome the range migration and realize the phasecoherent integration of echo energy.The expression of target offset caused by matching filter is given to avoid the error of range estimation.in the conventional algorithm.Experimental results show that the proposed algorithm has low computational complexity and the detection performance is close to that of the full-parameter space search algorithm.3.A range migrating radar target energy-focusing and detection algorithm based on blind speed side lobe suppression is proposed.Two sets of complementary window functions were designed.Firstly,the blind speed side lobe is forced to split through the window functions of group A and group B,and the blind speed side lobe is inhibited by the minimum operation.The resulting blind speed side lobe residual terms are complementary and overlapped in the distance dimension.In this algorithm,the target background is modeled as Gaussian white noise,the influence of two-level minimization on Gaussian white noise is analyzed,the relationship between false alarm probability and detection threshold is derived,and an iterative algorithm is designed to determine the detection threshold corresponding to a specific false alarm probability.The effectiveness of the iterative algorithm is verified by experiments.Due to the two-level minimization operation,this algorithm can suppress the noise greatly and obtain a higher output signal-to-noise ratio.Experimental results show that the proposed algorithm is superior to the similar algorithms in terms of blind speed side lobe suppression and anti-noise performance,and the radar operation mode does not need to be changed.4.A range migrating target detector against compound Gaussian clutter background is proposed.The clutter was modeled as a compound Gaussian model,the range migration of the target was considered,and the point target and range extended target detectors were designed based on Rao criterion.As the range migration of the target is considered,good phase-coherent integration performance can be obtained.The two detectors do not need to estimate the echo amplitude parameters of the target,which avoids iterative operation,and the theoretical derivation shows that the detection statistics of the range extended target can be regarded as the superposition of the detection statistics of the point target,which is convenient for the actual implementation.The range extended target detector takes into account the echo energy of multiple scattering points and has higher detection performance.Experiments show that the proposed detector has higher detection probability than similar detectors.