【摘要】：合成孔徑雷達(dá)(SAR)能夠在所有的照明/天氣條件下產(chǎn)生觀察場景的高分辨率微波圖像。復(fù)雜運(yùn)動平臺SAR以戰(zhàn)斗機(jī)為載體由于受到外界干擾偏離理想運(yùn)動狀態(tài)使得運(yùn)行軌跡為三維曲線,傳統(tǒng)成像算法不再適用。因此如何實(shí)現(xiàn)復(fù)雜運(yùn)動平臺SAR對觀察場景高分辨率成像亟待研究。本文建立了復(fù)雜運(yùn)動平臺SAR模型,詳細(xì)分析了復(fù)雜運(yùn)動SAR與理想運(yùn)動SAR的區(qū)別以及適用于運(yùn)動誤差較小和較大兩種情況下的復(fù)雜運(yùn)動成像算法。主要內(nèi)容分為以下三個(gè)部分:首先本文從運(yùn)動誤差、相位誤差、多普勒參數(shù)和方位向分辨四個(gè)方面重點(diǎn)分析了復(fù)雜運(yùn)動SAR與理想運(yùn)動SAR的區(qū)別。在運(yùn)動誤差方面得出方位向回波信號為非線性調(diào)頻信號,如果不運(yùn)動補(bǔ)償將導(dǎo)致方位向的非均勻采樣。在相位誤差方面分析了不同階數(shù)相位誤差對回波信號的影響。在方位向分辨率方面對理論方位向分辨率進(jìn)行了重新定義:方位向回波信號脈沖壓縮后主瓣-3dB寬度。在多普勒參數(shù)方面分析了使不同運(yùn)動模型下得復(fù)雜運(yùn)動SAR的多普勒帶寬展寬的加速度容限同時(shí)分析了復(fù)雜運(yùn)動多普勒歷程的空變性,得出復(fù)雜運(yùn)動SAR需采用BP算法對場景進(jìn)行逐點(diǎn)成像。然后本文介紹了適用于運(yùn)動誤差較小情況下的復(fù)雜運(yùn)動成像算法:基于IMU實(shí)測數(shù)據(jù)的BP算法。首先通過成像指標(biāo)得到Legendre正交多項(xiàng)式為該算法高階擬合的最優(yōu)基函數(shù)結(jié)論,然后得出了保證該算法不失效的加速度、速度和位置測量誤差容限,此算法只適用于小測量誤差情況,當(dāng)測量誤差較大時(shí)需要采取基于回波數(shù)據(jù)參數(shù)估計(jì)的BP算法。最后本文介紹了適用于運(yùn)動誤差較大情況下的復(fù)雜運(yùn)動成像算法:基于反解Legendre系數(shù)強(qiáng)點(diǎn)信息相位跟蹤的BP算法。研究了信雜比對相位跟蹤算法的影響,得出信雜比門限,重點(diǎn)分析了強(qiáng)點(diǎn)個(gè)數(shù)和幾何分布對雷達(dá)位置求解的影響,然后通過設(shè)置合適的信雜比和強(qiáng)點(diǎn)個(gè)數(shù)并通過反解Legendre系數(shù)得出雷達(dá)平臺的斜距史,構(gòu)造BP算法相位補(bǔ)償因子并應(yīng)用于BP算法對場景成像,驗(yàn)證了算法的有效性。
[Abstract]:Synthetic Aperture Radar (SAR) (SAR) can generate high resolution microwave images of observation scenes under all illumination / weather conditions. Because the complex motion platform SAR uses fighter plane as the carrier and deviates from the ideal state of motion due to the external interference, the trajectory is 3D curve, so the traditional imaging algorithm is no longer applicable. Therefore, how to realize the complex motion platform SAR for high resolution imaging of observation scene needs to be studied urgently. In this paper, the SAR model of complex motion platform is established, and the difference between complex motion SAR and ideal motion SAR is analyzed in detail, as well as the complex motion imaging algorithm suitable for the case of small and large motion error. The main contents are divided into the following three parts: firstly, this paper analyzes the difference between SAR of complex motion and SAR of ideal motion from four aspects: motion error, phase error, Doppler parameter and azimuth resolution. The result shows that the azimuth echo signal is a nonlinear frequency modulated signal, and if the motion is not compensated, it will lead to the non-uniform sampling in the azimuth direction. In the aspect of phase error, the effect of phase error of different order on echo signal is analyzed. The theoretical azimuth resolution is redefined in the aspect of azimuth resolution: the main lobe-3dB width after pulse compression of azimuth echo signal. In terms of Doppler parameters, the acceleration tolerance of Doppler bandwidth broadening for complex motion SAR under different motion models is analyzed, and the void variation of complex motion Doppler history is also analyzed. It is concluded that SAR with complex motion needs to use BP algorithm to image the scene point by point. Then this paper introduces the complex motion imaging algorithm which is suitable for the case of small motion error: BP algorithm based on the measured data of IMU. The conclusion that Legendre orthogonal polynomial is the optimal basis function for high order fitting of the algorithm is obtained by imaging index, and then the tolerance of acceleration, velocity and position measurement error to ensure that the algorithm does not fail is obtained. This algorithm is only suitable for small measurement errors. When the measurement error is large, the BP algorithm based on echo data parameter estimation should be adopted. Finally, this paper introduces a complex motion imaging algorithm suitable for large motion errors: a BP algorithm based on phase tracking of strong point information based on inverse solution of Legendre coefficients. The influence of signal-clutter ratio on phase tracking algorithm is studied, and the threshold of signal-to-clutter ratio is obtained. The influence of the number of strong points and geometric distribution on the radar position is analyzed. Then by setting the appropriate signal to clutter ratio and the number of strong points and inverse solving the Legendre coefficient to obtain the oblique distance history of the radar platform, the phase compensation factor of the BP algorithm is constructed and applied to the scene imaging of the BP algorithm, which verifies the effectiveness of the algorithm.
【學(xué)位授予單位】：電子科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TN957.52

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