本文選題：幾何光學物理光學法 + 電磁散射��； 參考：《西安電子科技大學》2014年碩士論文

【摘要】：通過電磁仿真模擬雷達回波,研究空間目標的逆合成孔徑雷達(ISAR)成像,能獲得其運動態(tài)勢和基本結(jié)構(gòu)特征,同時也能為目標分類、識別等提供理論模型和技術(shù)支撐。盡管ISAR成像技術(shù)已發(fā)展到較高水平,但由于空間目標的特殊性,仍有不少問題有待解決。論文基于目標電磁散射的基本原理和模型,開展運動空間目標ISAR成像仿真的研究工作,主要內(nèi)容包括:1、針對空間目標(衛(wèi)星)的天線結(jié)構(gòu)特點,利用幾何光學-物理光學法(Geometrical optics and Physical optics,GOPO)混合高頻近似算法計算空間目標的電磁散射特性。首先通過簡單目標(二面角反射器和簡單組合體)驗證GOPO的可行性和有效性。著重利用該算法分別計算了飛機模型和衛(wèi)星模型在不同方位角和入射角下的垂直極化和水平極化的雷達散射截面(Radar Cross Section,RCS)。由于衛(wèi)星結(jié)構(gòu)的對稱性和在計算散射場時采用PO算法,垂直極化(VV極化)散射結(jié)果與水平極化(HH極化)差別不大。對比計算了完整衛(wèi)星模型和去掉天線結(jié)構(gòu)的衛(wèi)星模型在不同方位角和入射角下的RCS,可以發(fā)現(xiàn):由于衛(wèi)星天線具有明顯的角形結(jié)構(gòu),使得多次散射效應加強,因此在一定角度范圍內(nèi),天線的多次散射占主導因素。2、綜述逆合成孔徑雷達(Inverse Synthetic Aperture Radar,ISAR)成像的基本原理,分析了ISAR成像中散射場與成像函數(shù)的關(guān)系。模擬了飛機和衛(wèi)星模型的一維距離像和一維方位像,并給出了完整衛(wèi)星模型和無天線結(jié)構(gòu)模型的二維ISAR像,討論不同帶寬和采樣點數(shù)對飛機成像結(jié)果的影響�；诰嚯x-多普勒(Range-Doppler)成像算法,分析了目標方位向的多普勒頻移效應,利用頻率步進信號(SFCW)分別模擬了飛機點散射模型和實際衛(wèi)星模型的雷達回波,在距離-多普勒域進行ISAR成像仿真。由衛(wèi)星成像結(jié)果可以明顯看出有無天線的影響,加強論證了角反射器對目標電磁散射特性的影響。3、研究了ISAR成像中運動補償算法。討論了ISAR成像過程由于目標運動出現(xiàn)的多普勒效應,由于目標的運動可能會引起方位像模糊和距離徙動的現(xiàn)象,因此需要在ISAR成像過程中進行平動補償和旋轉(zhuǎn)運動補償。對標準的平動補償和轉(zhuǎn)動補償過程做了簡要的分析,并據(jù)此提出了最小熵法和聯(lián)合時頻分析的運動補償方法,從結(jié)果可以看出,前者主要補償目標的平動分量,后者則可以補償目標的平動和轉(zhuǎn)動分量,有效提高了成像質(zhì)量。并以衛(wèi)星模型為算例,基于GOPO算法模擬的雷達電磁回波,仿真了不同參數(shù)(帶寬、運動速度等)情況下的ISAR成像。結(jié)果表明:當增加雷達帶寬時,圖像中目標散射強點在距離向的分布更加清晰;當增大目標轉(zhuǎn)動速度時,圖像中目標散射強點在方位向的分布更加清晰,同時衛(wèi)星翼板部分有一定增強。
[Abstract]:The inverse synthetic Aperture Radar (ISAR) imaging of space targets can be studied by electromagnetic simulation to simulate the radar echo, which can obtain the motion situation and basic structural characteristics, and also provide theoretical model and technical support for target classification and recognition. Although ISAR imaging technology has been developed to a higher level, there are still many problems to be solved because of the particularity of space targets. Based on the basic principle and model of target electromagnetic scattering, the research work of ISAR imaging simulation of moving space target is carried out in this paper. The main contents include: 1, aiming at the antenna structure characteristics of space target (satellite). The hybrid high-frequency approximation algorithm of geometric optics and physical optics (GOPO) is used to calculate the electromagnetic scattering characteristics of space targets. Firstly, the feasibility and effectiveness of GOPO are verified by simple target (dihedral reflector and simple combination). The radar cross section (RCS) of vertical and horizontal polarization of aircraft model and satellite model at different azimuth and incident angles are calculated respectively by using this algorithm. Due to the symmetry of satellite structure and the use of PO algorithm in the calculation of scattering field, the vertical polarization (VV polarization) scattering results are not different from horizontal polarization (HH polarization). The RCSs of the complete satellite model and the satellite model without antenna structure at different azimuth and incident angles are compared and calculated. It is found that the multiple scattering effect is enhanced because of the obvious angular structure of the satellite antenna. Therefore, in a certain range of angles, multiple scattering of antenna is the dominant factor. This paper summarizes the basic principle of inverse synthetic Aperture radar (ISAR) imaging, and analyzes the relationship between scattering field and imaging function in ISAR imaging. The one-dimensional range profile and one-dimensional azimuth image of the aircraft and satellite model are simulated, and the complete satellite model and the two-dimensional ISAR image without antenna structure are given. The effects of different bandwidth and sampling points on the imaging results of the aircraft are discussed. Based on Range-Doppler imaging algorithm, Doppler frequency shift effect of target azimuth direction is analyzed. Radar echo of aircraft point scattering model and actual satellite model is simulated by frequency step signal (SFCW). ISAR imaging simulation is carried out in range-Doppler domain. The influence of antenna can be clearly seen from the results of satellite imaging. The influence of angle reflector on the electromagnetic scattering characteristics of target is demonstrated. The motion compensation algorithm in ISAR imaging is studied. This paper discusses the Doppler effect in ISAR imaging process due to the target motion, because the target motion may cause azimuth image blur and range migration, so it is necessary to compensate for translation and rotation motion in ISAR imaging process. Based on the analysis of the standard translation compensation and rotational compensation process, the minimum entropy method and the motion compensation method of joint time-frequency analysis are proposed. From the results, it can be seen that the translational component of the former is the main compensation target. The latter can compensate the translational and rotational components of the target and improve the imaging quality effectively. Taking the satellite model as an example, the ISAR imaging with different parameters (bandwidth, velocity, etc.) is simulated based on the radar electromagnetic echo simulated by the GOPO algorithm. The results show that when the radar bandwidth is increased, the distribution of the target scattering intensity in the range direction is more clear, and when the target rotation velocity is increased, the distribution of the target scattering strength in the azimuth direction becomes clearer. At the same time, the satellite flange part has certain enhancement.
【學位授予單位】：西安電子科技大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TN957.52

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相關(guān)期刊論文 前1條

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本文編號：2090303