Research On CFAR Detection Method Of Radar Ship Target In Heterogeneous Sea Condition

Radar plays an important role in modern information warfare,and is widely used in the field of national defense and security.The detection and recognition of radar target has become a hot research topic in many countries.Among them,the constant false alarm rate(CFAR)detection method is widely used in the automatic detection and tracking of radar target on the sea as a technology that can adjust the threshold according to the change of environment.With the continuous efforts of researchers in various countries,many excellent CFAR detection methods have been proposed and achieved good detection results in uniform sea conditions.However,it is difficult to keep the performance balance of these detection methods in non-uniform sea conditions,such as including strong speckle noise,dense target distribution,strong clutter edge and so on.At present,there are two main difficulties in ship target detection on the sea: one is that it is difficult to detect the target accurately and efficiently in non-uniform sea conditions;the other is that there are obvious performance bottlenecks in weak target detection affected by its own scattering characteristics,environment and radar equipment parameters.In this paper,we will carry out the research from these two aspects,and use a variety of radar measured data to verify and analyze the research results,including X-band solid-state coherent radar one-dimensional data,Terrasar-X data and Gaofen-3 data.The main contents are as follows:(1)Based on the in-depth study of the CFAR detection mechanism of radar target,the traditional CFAR detection methods are demonstrated and analyzed by experiments.Aiming at the problem that the detection accuracy of the traditional CFAR detection methods decreases under the non-uniform sea conditions such as dense target distribution and strong clutter edge,and a CFAR based on adaptive truncation depth(ATD-CFAR)is proposed.ATD-CFAR can remove the interference pixels in the local reference window almost completely,and keep the real sea clutter samples greatly.Compared with the traditional CFAR,this method can estimate the parameters more accurately,achieve lower false alarm rate and greatly improve the target detection accuracy in non-uniform sea conditions.(2)With the launch of advanced high resolution synthetic aperture radar(SAR)satellites,more information can be obtained from the image,such as the spatial relationship between pixel points and pixel points in the internal structure of warship targets.Therefore,this paper designs an improved target detection method of bilateral CFAR(IB-CFAR)in complex environment.IB-CFAR can improve the contrast information between the target and the surrounding clutter to the greatest extent without changing the basic distribution of the actual sea conditions.At the same time,the structure information of the ship is described in detail while the target detection rate is further improved under the non-uniform sea condition.Moreover,the similarity information between pixels in the weak target can be improved and all kinds of weak targets can be detected well in complex environment.(3)In this paper,we design a set of radar target CFAR detection system under non-uniform sea conditions.Each algorithm has detailed theoretical support,and is also tested and verified repeatedly in various non-uniform sea conditions.At the same time,the system provides a series of related functions,such as SAR image selection,SAR image preprocessing,detection performance index,route planning,flow monitoring,data display and image display,which can realize radar target detection under non-uniform sea conditions.