Research On Moving Target Detection And FPGA Implementation Technology In Sea Clutter

Moving targets detection in sea clutter background is a hot research topic in the field of radar signal processing, and it plays an important role in both civil and military. With the increasing requirements of range distance, Doppler resolution, range resolution, real-time and reliability, how to improve signal-to-clutter(SCR) of radar echo and effectively detect moving targets in strong sea clutter are pressing research problems. As sea clutter seriously affects the detection of low-speed and high-speed moving target, in the thesis, research work was carried out on moving target detection algorithms and FPGA implementation technology under the background of sea clutter on the basis of studying the characteristics of moving targets.Firstly, the statistical distribution characteristics of different sea clutter models were analyzed in detail. And echo models were set up based on the research on the characteristics of low-speed targets, such as ship and fishing boat, as well as high speed targets, like missile, aircraft, etc. Then time-domain and frequency-domain features of moving targets were discussed and simulated.Secondly, taken the phenomenon that Doppler frequency of low-speed moving targets was easily close to the sea center frequency of sea clutter into consideration, optimal detection(OD) and generalized likelihood ratio test(GLRT) of low-speed moving targets in K-distributed clutter background were studied and discussed in detail. Then the detection performance of OD and GLRT was compared on following aspects, i.e., coherent integrated pulse number, shape parameter and scale parameter of K-distributed clutter. Furthermore, auxiliary clutter range units were used to estimate the normalized covariance matrix of sea clutter. Two algorithms, i.e., eigenvalue decomposition and phase search which computation was improved, were taken to calculate the Doppler frequency of moving target. Numerical Monte Carlo experiments were provided to compare and analyze the detection performance of OD and GLRT. And the performance of GLRT under the condition of unknown Doppler steering vector was simulated. Also the IPIX sea clutter was processed to demonstrate the effectiveness of GLRT detector.Thirdly, Keystone transform(KT) and Radon-Fourier transform(RFT) were studied and discussed to detect high-speed moving targets because there were range migration and Doppler fuzzy in a long time coherent integration. Three different KT ways were analyzed and compared to compensate for range walk of moving target. Based on the coupling relationship among radial velocity, range migration and Doppler frequency of moving target’s echo, RFT method was realized via searching radial velocity and range. However, as a result of discrete pulse sampling, the “blind speed side-lobe(BSSL)” of RFT may inevitably appear in real applications. Thus complementary weighting function was introduced to Doppler filter function to suppress BSSL. Furthermore, abundant Monte Carlo experiments were carried to compare the detection performance of KT and RFT under the background of sea clutter.Finally, based on the study and analysis of these methods, FPGA simulations of GLRT algorithm for low-speed moving targets was implemented under the ISE software environment, and the results were compared with those of MATLAB.In summary, low-speed or high-speed targets in sea clutter could be effectively detected under low signal-ratio-clutter(SCR) was via the proposed methods.