Research On Target Detection Technology In Sea Clutter Background

Sea clutter suppression and target detection technology have always been hotspots and difficulties in the field of current radar signal processing.Due to the complexity of the mechanism of sea clutter generation,for slow and weak target on the sea surface and floating target,the Doppler spectrum of the target and that of the sea clutter are aliased,and the target is submerged by strong sea clutter.Traditional methods based on frequency domain filtering are difficult to extract the target.In order to meet the high requirements of modern radar target detection,based on the measured data of sea surface echo,it is a significant research direction to deeply study and analyze the characteristics of sea clutter and target,and design a target detection algorithm with good performance according to the characteristic differences of the two.Based on the actual sea surface echo data measured by IPIX radar,this thesis focuses on the target detection technology in the background of sea clutter.Firstly,it analyzes the nature of sea clutter in detail based on the measured sea clutter data,on this basis,this thesis carries out research on the detection of slow and weak target and floating target on the sea surface based on the difference of oscillation characteristic and chaotic characteristic between sea clutter and target,the effectiveness and advantages of related algorithms are verified through simulation experiments.The main work and innovations of this thesis are as follows:1.On the basis of the sea surface echo data set measured by the IPIX radar,the statistical characteristic of amplitude distribution,chaotic characteristic,time corelation,space corelation and oscillation characteristic of the sea clutter are studied and analyzed in depth by the means of theoretical analysis combined with the verification of measured data.2.According to the difference of oscillation characteristic between sea clutter and target echo,the idea of sparse representation is introduced,using morphological component analysis(MCA)to establish a constrained optimization model for sea surface echo,and an adoptive tunable Q wavelet transform(A-TQWT)algorithm is designed.On this basis,an A-TQWT-based sea surface detection algorithm for slow and weak moving target is proposed;the simulation results show that this algorithm can effectively detect slow and weak moving target falling into the sea clutter Doppler channel,and the suppression of sea clutter is adaptive,does not require any prior information about clutter and the target,so it has good engineering practical value.3.Based on the measured sea surface echo data,it is proved that the sea surface echo time series has chaotic characteristic.And the permutation entropy(PE)and weighted permutation entropy(WPE)characteristics of the sea surface echo time series are studied,which used to describe the complexity and randomness information of the clutter and the target.After these research,this thesis proves the feasibility of distinguishing the sea clutter and the target by the PE and WPE features of the sea surface echo time series,and compared with the PE feature,the WPE feature has better ability to distinguish the sea clutter and the target.On this basis,a target detection algorithm based on WPE characteristic of sea surface echo time series is proposed,and the performance of the algorithm is verified based on measured data under three different sea state conditions:high,medium and low.4.The idea of variational mode decomposition(VMD)is introduced,and an adaptive variational mode decomposition(A-VMD)algorithm based on the correlation index is developed.When the sea surface echo signal is decomposed adaptively,the intrinsic mode function(IMF)components with good discrimination between the sea clutter and the target are selected for reconstruction.On this basis,it is proved that the WPE feature of the reconstructed signal after A-VMD decomposition which compared with the WPE feature of the original signal has a better ability to distinguish between the target and the sea clutter,and then a sea target detection algorithm based on the combination of A-VMD and WPE feature is proposed.The effectiveness is verified by the measured data based on simulations.Simulation results show that the algorithm has a stronger feature discrimination ability and can effectively detect weak target floating on the sea surface under three different sea conditions: high,medium and low.