發(fā)布時間：2018-06-21 02:42

  本文選題：旋轉(zhuǎn)式合成孔徑雷達 + 雙基合成孔徑雷達��； 參考：《西安電子科技大學》2014年博士論文

【摘要】：合成孔徑雷達(Synthetic Aperture Radar, SAR)成像是一種全天時、全天候的微波遙感技術；在地球觀測、環(huán)境監(jiān)測、軍事偵察及飛行器安全飛行和降落等方面具有重要意義。為提高SAR系統(tǒng)性能，擴展其應用平臺，國內(nèi)外開展了新型SAR技術研究。直升機載旋轉(zhuǎn)式SAR利用雷達天線的旋轉(zhuǎn)來合成方位向孔徑，從而得到高分辨二維SAR圖像。它具有高時空分辨率、短重訪周期、前視成像能力、結(jié)構(gòu)簡單硬件成本低等優(yōu)點，且二維成像時不需要直升機平臺做任何運動。另外，結(jié)合直升機平臺運動和天線旋轉(zhuǎn)可合成虛擬二維面陣天線，同時融合距離脈沖壓縮技術可實現(xiàn)對觀測區(qū)域的三維成像。雙基SAR是指發(fā)射機和接收機位于不同平臺上的新型SAR模式。與單基SAR相比，雙基SAR具有可獲得目標非后向散射特征、系統(tǒng)設計靈活及便于接收機隱身設計等優(yōu)點。特別地，大斜視雙基SAR可以不需要飛越某一地區(qū)而能對該區(qū)域的目標進行探測；即也具有對前方目標成像能力。因此，作為對具有前方目標成像能力的新型SAR模式，直升機載旋轉(zhuǎn)式SAR和雙基SAR具有廣泛的軍事和民用前景。 本文在國家自然科學基金和國家973項目支撐下，圍繞直升機載旋轉(zhuǎn)式SAR和雙基SAR原理和成像算法展開研究，主要創(chuàng)新點如下： 1、針對直升機載旋轉(zhuǎn)式SAR方位分辨率依賴于方位重構(gòu)角的大小，傳統(tǒng)的劃分子孔徑的方法使得方位分辨率低的問題。在詳細分析其成像幾何模型基礎上，使用高階逼近原理近似構(gòu)造直升機載旋轉(zhuǎn)式SAR的回波信號模型，然后借助級數(shù)反演法求得其精確的二維頻譜表達式。在此基礎上，提出了一種高分辨直升機載旋轉(zhuǎn)式SAR成像算法，給出算法的完整推導過程和各補償因子的表達式；并詳細分析了系統(tǒng)參數(shù)選擇對直升機載旋轉(zhuǎn)式SAR分辨率的影響。 2、針對直升機載旋轉(zhuǎn)式SAR雷達天線旋轉(zhuǎn)成像時平臺存在運動的問題。提出一種融合直升機平臺運動補償?shù)母倪MChirp Scaling算法。該算法首先建立了存在平臺運動時直升機載旋轉(zhuǎn)式SAR成像的幾何模型。在此基礎上，詳細分析平臺運動引起的目標斜距誤差在單個孔徑時間內(nèi)隨目標位置的變化關系，得到了平臺運動誤差的空變性大小并給出誤差補償方法。然后，分析了直升機載旋轉(zhuǎn)式SAR幾何構(gòu)型帶來的速度隨目標位置變化特性對成像質(zhì)量的影響，并把其影響補償融入到Chirp Scaling算法的距離徙動空變性校正和方位壓縮中。整個算法只包含快速傅立葉變換和復數(shù)乘操作，不涉及插值，易于工程實現(xiàn)。最后，計算機仿真結(jié)果表明，該算法能夠?qū)χ鄙龣C平臺運動時大場景進行成像并具有良好的成像效果。 3、提出了一種基于調(diào)頻連續(xù)波(Frequency Modulated Continuous Wave, FMCW)的直升機載旋轉(zhuǎn)式SAR新的成像模式并給出了相應的成像算法。該方法首先利用等效相位中心原理，將收發(fā)分置天線系統(tǒng)的回波信號等效為“自發(fā)自收”單基系統(tǒng)。在此基礎上，求得了其精確的二維頻譜同時分析了雷達天線連續(xù)運動的影響--產(chǎn)生多普勒頻移，并給出補償方法；然后運用高效的逆Chirp-Z變換校正了距離徙動空變性。詳細分析了速度近似誤差對成像區(qū)域大小的影響，并把其影響補償融合到成像算法中。整個算法只包含快速傅立葉變換和復乘操作，不涉及插值，易于工程實現(xiàn)。最后，，仿真結(jié)果驗證了分析結(jié)論的正確性和算法的有效性。 4、結(jié)合直升機平臺的運動和安裝在旋翼末端的雷達天線的旋轉(zhuǎn)，直升機旋轉(zhuǎn)式SAR能實現(xiàn)對載機前方目標的三維成像。本文根據(jù)直升機載旋轉(zhuǎn)式SAR幾何構(gòu)型和回波信號特性，提出一種新的直升機載旋轉(zhuǎn)式SAR前視三維成像算法。該算法首先將雷達天線旋轉(zhuǎn)得到回波數(shù)據(jù)采用改進Chirp Scaling算法處理獲得單幅SAR圖像；然后把沿每個方位向?qū)男本?沿航向平面的切片數(shù)據(jù)看成前下視成像模式的回波數(shù)據(jù)，利用融合子場景劃分技術的Omega-k成像算法沿方位依次進行成像處理，最后獲得直升機平臺前方目標的三維圖像。仿真結(jié)果驗證了該算法的有效性和正確性。該模式僅僅利用了一根天線就能獲得載機平臺前方目標的三維SAR圖像，具有結(jié)構(gòu)簡單、成本低等優(yōu)勢。 5、在大斜視方位時變雙基SAR模式下，一方面，距離走動校正引入的距離偏移外，方位時變的幾何構(gòu)型也引入一個距離偏移。尤其是在接收和發(fā)射平臺航線夾角較大時，幾何構(gòu)型引入的空變性變得更劇烈。另一方面，隨著斜視角的增大，方位調(diào)頻率高次項和三次相位的空變性已經(jīng)不能忽略。針對該問題，提出一種改進的方位非線性調(diào)頻變標算法。該方法首先在距離頻率-方位時域完成距離走動和多普勒中心校正，然后在二維頻域通過一致二次距離壓縮校正剩余的距離單元徙動和距離-方位高次耦合。在分析方位時變雙基SAR幾何構(gòu)型引入的方位空變性、方位調(diào)頻率高次項和三次相位空變特性的基礎上，推導出變標函數(shù)的系數(shù)。相比傳統(tǒng)的非線性調(diào)頻變標算法，該算法沒有增加任何多余處理步驟。該算法可以有效的提高雙基SAR成像性能，極大的擴展方位向聚焦深度。
[Abstract]:Synthetic Aperture Radar (SAR) imaging is a all-weather, all-weather microwave remote sensing technology. It is of great significance in the aspects of earth observation, environmental monitoring, military reconnaissance and aircraft safety flight and landing. In order to improve the performance of the SAR system and expand its application platform, a new study of the new SAR technology has been carried out at home and abroad. The airborne rotating SAR uses the rotation of the radar antenna to synthesize the azimuth aperture, thus obtaining the high resolution two-dimensional SAR image. It has the advantages of high spatial resolution, short revisit period, forward-looking imaging ability, simple hardware cost and so on, and does not need any motion in the helicopter platform during two-dimensional imaging. In addition, it is combined with the helicopter platform. The virtual two-dimensional array antenna can be synthesized by the motion and the antenna rotation, and the 3D imaging of the observed area can be realized by the fusion of the distance pulse compression technology. The dual base SAR is a new SAR mode on the transmitter and receiver on different platforms. Compared with the single base SAR, the dual base SAR can obtain the non backscattering characteristics of the target, and the system is flexible and convenient for the system design. In particular, the large strabismus dual base SAR can detect the target in the region without flying over a certain area; that is, it also has the ability to imaging the target in front of the target. Therefore, as a new SAR model for the imaging capability of the front target, the airborne rotary SAR and double base SAR are widely military. And the future of civilian use.
Based on the support of the National Natural Science Fund and the national 973 project, the helicopter rotary SAR and bistatic SAR imaging algorithm and principle research, the main innovations are as follows:
1, in view of the size of azimuth resolution in the azimuth resolution of the helicopter loaded rotating SAR, the traditional method of dividing the sub aperture makes the azimuth resolution low. On the basis of the detailed analysis of its imaging geometry model, the high order approximation principle is used to approximate the echo signal model of the helicopter loaded rotating SAR, and then the series inverse is used. On this basis, a high resolution helicopter rotating SAR imaging algorithm is proposed, the complete derivation process of the algorithm and the expression of the compensation factors are given, and the influence of the selection of the system parameters on the helicopter's rotating SAR resolution is analyzed in detail.
2, an improved Chirp Scaling algorithm is proposed for the motion compensation of helicopter carrier rotating SAR radar antenna during rotation imaging. This algorithm first establishes a geometric model of helicopter rotating SAR imaging in the presence of platform motion. On this basis, the platform motion is analyzed in detail. The spatial variability of the motion error of the platform is obtained and the error compensation method is given. Then, the effect of the velocity of the helicopter's rotating SAR geometry on the image quality is analyzed, and the compensation is incorporated into the C. Hirp Scaling algorithm is used for distance migration and azimuth compression. The whole algorithm only contains fast Fu Liye transform and complex multiplying operation, which does not involve interpolation and is easy to implement. Finally, the computer simulation results show that the algorithm can image the large field scene in the motion of the helicopter platform and have good imaging effect.
3, a new imaging mode of helicopter borne rotating SAR based on Frequency Modulated Continuous Wave (FMCW) is proposed and the corresponding imaging algorithm is given. The method first uses the principle of the equivalent phase center to equip the echo signal of the receiving and receiving antenna system as a "spontaneous self receiving" single base system. At the same time, the exact two-dimensional spectrum is obtained and the influence of the continuous motion of the radar antenna is analyzed at the same time - the Doppler shift is produced and the compensation method is produced. Then the high efficient inverse Chirp-Z transform is used to correct the distance migration. The influence of the velocity approximation error on the size of the imaging region is analyzed in detail, and the compensation is fused. Imaging algorithm. The algorithm contains only the fast Fu Liye transform and complex multiplication operation, does not involve interpolation, easy to realize. Finally, the simulation results verify the correctness and validity of algorithm analysis.
4, combined with the motion of the helicopter platform and the rotation of the radar antenna installed at the end of the rotor, the helicopter rotating SAR can realize the three-dimensional imaging of the target in front of the carrier. In this paper, a new helicopter borne rotating SAR forward vision 3D imaging algorithm is proposed based on the helicopter's rotating SAR geometry and echo signal. First, the radar antenna is rotated to get the echo data, and the single SAR image is obtained by the improved Chirp Scaling algorithm. Then the slice data of the corresponding oblique distance and direction plane are regarded as the echo data of the front and down view imaging mode, and the Omega-k imaging algorithm using the fusion sub scene division technique is sequentially performed along the azimuth. A three-dimensional image processing, finally get the helicopter platform in front of the goal. The simulation results verify the validity and correctness of the algorithm. The 3D SAR image mode using just one antenna can obtain the aircraft platform in front of the goal, has the advantages of simple structure, low cost advantages.
5, in the dual base SAR mode in the azimuth of large strabismus, on the one hand, the geometric configuration of azimuthal time shift is also introduced by the distance migration from the distance shift correction introduced by the distance moving correction. Especially, the space variability introduced by the geometric configuration becomes more violent when the angle of the route of the receiving and launching platforms is large. On the other hand, with the increase of the angle of view, the azimuth is increased. An improved azimuthal nonlinear frequency modulation (NLFM) scaling algorithm is proposed for the high frequency modulation rate and the three phase. This method first completes the distance travel and the Doppler center correction in the range frequency azimuth time domain, and then corrects the remaining distance units through a two distance compression in the two-dimensional frequency domain. On the basis of azimuthal space variability, azimuth frequency high order and three phase space variation, the coefficient of the variable function is derived on the basis of the analysis of azimuth SAR geometric configuration introduced in the azimuth time-varying dual base geometry. This algorithm does not increase any redundant processing steps compared to the traditional Nonlinear FM scaling algorithm. This algorithm is available. In order to effectively improve the imaging performance of bistatic SAR, the azimuth focusing depth is greatly expanded.
【學位授予單位】：西安電子科技大學
【學位級別】：博士
【學位授予年份】：2014
【分類號】：TN957.52

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