Research On Method And Implementation Of Low-altitude Targets Detection Based On Phased-array Radar

The multipath is the main factor that affects the low-altitude targets detection performance of radar.The echoes from different paths superpose on the receiver,and the total signal amplitude fluctuated strongly,so the detection performance descends rapidly.Focusing on low-altitude targets detection,this thesis researched the detection performance of frequency diverse array.As an important part of this thesis,the low altitude targets detector of frequency diverse array and constant false alarm detection module are implemented on FPGA.This thesis includes four main parts,and the main work of each part is stated as follow:1.By constructing the geometric propagation model of multipath,this thesis analyzed the influence on amplitude and power introduced by multipath propagation.And analyzed the main lobe division phenomenon of traditional phased array radar when it used to detecting low altitude targets,and compare the detection performance of MIMO radar and traditional phased array radar.2.This thesis conducted an in-depth study on the beam scanning characteristics and beam pointing angle controlling of frequency diverse array.By bring a small frequency difference between adjacent elements,the beam pointing angle is related to distance of radical direction,which is different with traditional phased array.Based on the research of beam scanning characteristics,this dissertation deduced the compute expression of the frequency difference,controlling the frequency difference enable the FDA irradiate target accurately.3.The low altitude targets detection performance of frequency diverse array has been researched.By building the echo signal model of FDA,this thesis deduced the observation matrix expression.Based on generalized likelihood ratio test,this thesis obtained and compared the detection performance under three different signals(regular pulse,OFDM,LFM)by numeric simulation,and concluded that LFM-FDA possess the advantage of OFDM and LFM,so LFM-FDA is more conducive to targets detection.4.The low-altitude targets detector of FDA and two-dimensional CFAR detection module are implemented on FPGA.Based on the expression of test statistic,this thesis designed the structure of FDA low-altitude targets detector and implemented it on FPGA and used the detector statistics the detected probability under several different signal-noise-ratio,and this detector include two modules,matrix multiple module and matrix determinant module.Based on low-altitude targets detection radar project background,this thesis designed and implemented two-dimensional CFAR processing module too.The two-dimensional CFAR processing module combined with other signal processing module can accomplish the detection of low-altitude targets.