【摘要】：逆合成孔徑雷達(Inverse Synthetic Aperture Radar,ISAR)能夠?qū)臻g、空中和海面運動目標進行全天時、全天候成像,在國家安全和國民經(jīng)濟領域擁有重大的應用價值。但是,對機動目標回波進行成像處理時仍然存在一些問題。機動運動狀態(tài)下,雷達回波信號運動補償后,仍然包含加速度等引入的高階相位項,導致重建二維圖像在方位向發(fā)生散焦,成像質(zhì)量下降。此外,步進頻率體制下,雷達回波信號會受到機動目標運動徑向速度和加速度影響,直接進行成像處理后重建一維距離像出現(xiàn)散焦和移位現(xiàn)象。針對上述問題,本文對機動運動目標的ISAR成像處理和一維距離像重建進行研究并提出解決方案。首先,本文介紹了ISAR成像的基本原理,包括ISAR轉(zhuǎn)臺成像模型和線性調(diào)頻信號,并且概述了成像基本技術脈沖壓縮和運動補償?shù)姆椒�。另�?通過實驗仿真飛機目標回波和RD成像算法,為后續(xù)的機動目標ISAR成像奠定了理論基礎。其次,詳細分析了強機動目標回波的特征,建立強機動目標立方相位信號(Cubic Phase Signal,CPS)模型。針對CPS中調(diào)頻率和二次調(diào)頻率導致的圖像方位向散焦問題,提出相位差分-調(diào)頻傅立葉變換算法。先估計出CPS的所有參數(shù)后重構目標回波信號,再運用RD算法進行成像,就可以獲得高分辨率的ISAR像。MATLAB仿真驗證本章算法能夠獲得較好的成像結(jié)果。然后,研究了目標機動運動對步進頻率脈沖回波信號一維距離像的影響。對機動運動引入的加速度和速度如何影響距離向成像進行了詳細分析,提出基于求和立方相位函數(shù)(Integrated Cubic Phase Function,ICPF)的參數(shù)估計方法,對目標運動參數(shù)進行精確估計。然后通過Dechirp技術完成運動補償,經(jīng)逆快速傅立葉變換后獲取高分辨率的一維距離像。同時,對步進頻率脈沖信號高分辨率成像進行了仿真,驗證了該方法的有效性。最后,對本文全部工作進行總結(jié),并對未來需要繼續(xù)研究的問題進行了展望。
[Abstract]:Inverse synthetic Aperture Radar (Inverse Synthetic Aperture Radar,ISAR) has great application value in the field of national security and national economy. However, there are still some problems in imaging maneuvering target echo. In the state of maneuvering motion, after the radar echo signal motion compensation, it still contains the high-order phase term, such as acceleration, which leads to the defocusing of the reconstructed two-dimensional image in the azimuth direction and the degradation of the imaging quality. In addition, the radar echo signal will be affected by the radial velocity and acceleration of maneuvering target under the stepwise frequency system. In order to solve the above problems, the ISAR imaging processing and one dimensional range image reconstruction of maneuvering targets are studied and solutions are proposed. Firstly, this paper introduces the basic principle of ISAR imaging, including the imaging model of ISAR turntable and LFM signal, and summarizes the methods of pulse compression and motion compensation. In addition, the experimental simulation of aircraft target echo and RD imaging algorithm provides a theoretical basis for the subsequent maneuvering target ISAR imaging. Secondly, the echo characteristics of strong maneuvering target are analyzed in detail, and the cubic phase signal (Cubic Phase Signal,CPS model of strong maneuvering target is established. Aiming at the problem of azimuth defocusing caused by frequency modulation and quadratic frequency modulation in CPS, a phase difference divide-FM Fourier transform algorithm is proposed. First, all the parameters of CPS are estimated, then the target echo signal is reconstructed, then the high resolution ISAR image can be obtained by using the RD algorithm. The simulation results of MATLAB show that the algorithm can obtain better imaging results. Then, the influence of target maneuvering on one-dimensional range profile of step frequency pulse echo signal is studied. The influence of acceleration and velocity on range imaging is analyzed in detail. A parameter estimation method based on summation cubic phase function (Integrated Cubic Phase Function,ICPF) is proposed to estimate the target motion parameters accurately. Then the motion compensation is accomplished by Dechirp technique, and the high resolution range profile is obtained by inverse fast Fourier transform. At the same time, the high resolution imaging of step frequency pulse signal is simulated, and the effectiveness of the method is verified. Finally, the paper summarizes all the work and looks forward to the problems that need to be studied in the future.
【學位授予單位】：南京郵電大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TN957.52

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