本文選題：合成孔徑雷達 + 前視成像算法��； 參考：《南京理工大學》2017年碩士論文

【摘要】：合成孔徑雷達(Syntheyic Aperture Radar,簡稱SAR)是一種能夠全天時全天候工作的成像雷達,可以在能見度極低的氣象條件下得到類似光學照相的高分辨雷達圖像,所以被廣泛地使用。將SAR成像技術與導彈導航相結合,能夠利用SAR圖像信息與慣性導航系統(tǒng)定位信息相比較,校對導航誤差,提高打擊效率。但是彈載平臺的SAR有前視、非勻速直線運動等特點,這使得傳統(tǒng)的成像方法無法獲得高分辨率的雷達圖像,所以本文結合導彈的運動特性,分別從平飛彈道和俯沖彈道兩種運動軌跡對彈載前視SAR成像方法進行了研究。在平飛彈道下,彈載前視SAR由于多普勒頻率變化小,所以存在成像盲區(qū),并且飛行方向兩側會出現(xiàn)具有相同多普勒歷程的對稱目標,導致成像出現(xiàn)左右模糊問題。本文首先根據平飛彈道下彈目間的幾何關系,推導出彈載前視SAR成像的目標回波信號模型,分析了時域下瞬時目標斜距的泰勒級數(shù)展開式以及式中各項對前視成像的影響;然后提出一種適用于平飛彈道下基于雙天線的彈載前視SAR的改進距離多普勒成像算法,并且利用雙天線模式下不同天線信號間的波程差,來解決左右模糊問題;最后通過仿真實驗驗證了算法的可行性。在俯沖彈道下,由于彈目間的相對運動導致回波信號發(fā)生嚴重的距離徙動現(xiàn)象,還會使得多普勒調頻斜率不斷變化,引起方位向嚴重的聚焦深度問題,成像的分辨率大大降低。通過分析俯沖彈道下彈載平臺的運動特點,構建其前視SAR成像的目標回波信號模型,并推導出二維回波信號的表達式;然后從頻域算法的角度出發(fā),提出一種適用于雙天線單平臺前視SAR成像系統(tǒng)的改進非線性頻調變標成像算法,采用線性距離走動校正、距離徙動校正和二次距離壓縮完成距離向與方位向的解耦合和距離向壓縮;接著采用非線性頻調變標操作校正多普勒頻率的空變性完成方位向壓縮;最后通過仿真實驗驗證了算法是否可行。本文針對平飛彈道與俯沖彈道的前視SAR,提出各自適用的成像算法,通過仿真實驗證明了成像算法的可行性,具有一定的理論參考價值。
[Abstract]:Synthetic Aperture Radar (SAR) is a kind of imaging radar which can work all day and all weather. It can get high-resolution radar images similar to optical photography under extremely low visibility, so it is widely used. The combination of SAR imaging technology and missile navigation can make use of the SAR image information to compare with the positioning information of inertial navigation system to correct the navigation error and improve the strike efficiency. However, the SAR of the projectile platform has the characteristics of forward view and non-uniform linear motion, which makes the traditional imaging method unable to obtain high-resolution radar images. So this paper combines the motion characteristics of the missile. The forward looking SAR imaging method of projectile is studied from two kinds of moving tracks of flat missile track and subduction trajectory respectively. Under the plane missile track, there is a blind area of imaging because of the small change of Doppler frequency, and the symmetrical target with the same Doppler course will appear on both sides of the flight direction, which leads to the problem of left and right blur in the imaging. In this paper, the target echo signal model of projectile forward SAR imaging is derived according to the geometric relationship between projectiles under the plane missile track, and the Taylor series expansion of instantaneous target oblique distance in time domain and the influence of each item in the expression on forward imaging are analyzed. Then an improved range Doppler imaging algorithm based on dual antennas for projectile forward looking SAR is proposed and the problem of left and right ambiguity is solved by using the wave range difference between different antenna signals in dual antenna mode. Finally, the feasibility of the algorithm is verified by simulation experiments. Under subduction trajectory, the relative motion between projectiles and objects leads to a serious range migration phenomenon of echo signal, and also makes the Doppler frequency modulation slope change continuously, causing a serious azimuth focusing depth problem, and the resolution of imaging is greatly reduced. By analyzing the motion characteristics of projectile platform under subduction trajectory, the target echo signal model of forward looking SAR imaging is constructed, and the expression of two-dimensional echo signal is deduced, and then from the point of view of frequency domain algorithm, An improved nonlinear frequency-modulated scalar imaging algorithm for dual-antenna single-platform forward-looking SAR imaging system is proposed, which adopts linear range walk correction. Range migration correction and secondary range compression complete the decoupling and range compression of range and azimuth direction, and then the null variation of Doppler frequency is corrected by nonlinear frequency modulation scaling operation to complete azimuth compression. Finally, the feasibility of the algorithm is verified by simulation experiments. In this paper, aiming at the forward looking SARs of the flat-missile track and the subduction trajectory, the imaging algorithms are proposed. The simulation results show that the imaging algorithm is feasible and has certain theoretical reference value.
【學位授予單位】：南京理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TN957.52

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