臨近空間SAR成像理論與成像方法研究
發(fā)布時(shí)間：2019-04-01 10:11
【摘要】：臨近空間指距地球表面20公里至200公里高度的空域,其20公里至50公里的底部區(qū)域氣壓較低、擾流平穩(wěn)、無云雨影響,適合浮空慢速平臺(tái)等飛行器飛行。承載于臨近空間慢速平臺(tái)的合成孔徑雷達(dá)(SAR)具有滯空時(shí)間長(zhǎng)、重訪周期短、觀測(cè)地域廣等優(yōu)點(diǎn),在敏感地區(qū)偵察和環(huán)境監(jiān)測(cè)等領(lǐng)域具有重要的應(yīng)用價(jià)值。臨近空間慢速平臺(tái)SAR具有許多不同于星載和機(jī)載雷達(dá)的特殊問題,需要探索研究,也是國(guó)際雷達(dá)界近年來研究的熱點(diǎn)。本文針對(duì)臨近空間慢速平臺(tái)SAR的回波模型、成像模式、成像算法、運(yùn)動(dòng)補(bǔ)償、動(dòng)目標(biāo)檢測(cè)等核心問題進(jìn)行了理論研究和數(shù)值仿真,主要內(nèi)容如下:1、建立了臨近空間慢速平臺(tái)SAR的回波模型,分析了距離徙動(dòng)、多普勒、距離方位耦合、空變等回波特性,為成像模式、成像算法的研究提供了理論依據(jù)。2、提出時(shí)分多視角共孔徑成像模式,可有效利用慢速運(yùn)動(dòng)的冗余時(shí)間資源,對(duì)不同視角成像區(qū)域進(jìn)行方位錯(cuò)位采樣,為實(shí)現(xiàn)大場(chǎng)景快速成像提供了一種新的解決方案。3、提出基于非均勻傅里葉變換(NUFFT)的沿航向運(yùn)動(dòng)誤差補(bǔ)償方法,通過變標(biāo)因子將時(shí)域非均勻樣本在頻域?qū)崿F(xiàn)均勻化,可解決臨近空間慢速平臺(tái)沿航跡速度變化引起的成像主瓣展寬和旁瓣升高的問題。4、提出一種擴(kuò)展波數(shù)域處理的成像算法,通過在波數(shù)域處理過程中嵌入對(duì)回波二維頻譜的二維線性化和去空變處理,能夠解決恒定加速度條件下臨近空間慢速平臺(tái)SAR成像區(qū)外側(cè)的散焦和幾何失真問題。5、研究了一種基于多普勒參數(shù)均衡+FrFT的運(yùn)動(dòng)目標(biāo)成像方法,可利用距離徙動(dòng)校正后靜止與運(yùn)動(dòng)目標(biāo)的回波多普勒調(diào)頻率差異,分離動(dòng)靜目標(biāo)回波,實(shí)現(xiàn)單通道斜視模式下臨近空間慢速平臺(tái)SAR的動(dòng)目標(biāo)成像。以上模型和算法的有效性均經(jīng)過了仿真實(shí)驗(yàn)檢驗(yàn)。結(jié)果表明,上述研究工作可用于實(shí)現(xiàn)臨近空間慢速平臺(tái)SAR的高效高精度成像。
[Abstract]:The adjacent space refers to the airspace between 20 km and 200 km from the earth's surface. The air pressure in the bottom region of 20 km to 50 km is relatively low, the disturbance current is stable, and the influence of cloud and rain is free, so it is suitable for flying aircraft such as floating-air slow-speed platform and so on. The synthetic Aperture Radar (SAR), which is carried on the slow platform near the space, has the advantages of long lag time, short revisit period and wide observation area. It has important application value in the fields of reconnaissance and environmental monitoring in sensitive areas. The near-space slow-speed platform SAR has many special problems which are different from spaceborne and airborne radar. It needs to be explored and studied, and it is also a hot research topic in the international radar field in recent years. In this paper, the echo model, imaging mode, imaging algorithm, motion compensation, moving target detection and other core problems of the near-space slow-speed platform SAR are studied theoretically and numerically. The main contents are as follows: 1, The echo model of the near space slow platform SAR is established, and the echo characteristics of range migration, Doppler, range azimuth coupling and space variation are analyzed, which provides the theoretical basis for the study of imaging mode and imaging algorithm. A time division multi-angle common aperture imaging model is proposed, which can effectively utilize the redundant time resources of slow motion to sample the azimuth dislocation of different angle imaging regions, which provides a new solution for fast imaging of large scenes. A compensation method of heading motion error based on non-uniform Fourier transform (NUFFT) is proposed in this paper. The non-uniform samples in time domain are homogenized in frequency domain by scaling factor. It can solve the problem of the widening of the main lobe and the rise of the sidelobe caused by the variation of the velocity along the track of the near-space slow-speed platform. 4. An imaging algorithm based on extended wavenumber domain processing is proposed. By embedding the two-dimensional linearization and devoid processing of the echo two-dimensional spectrum in the wavenumber domain processing, the problem of defocusing and geometric distortion on the outside of the SAR imaging region of the near-space slow-speed platform under the condition of constant acceleration can be solved. A moving target imaging method based on Doppler parameter equalization FrFT is studied in this paper. After range migration correction, the Doppler modulation frequency difference between static and moving targets can be used to separate the echoes of static and moving targets. The moving target imaging of the near space slow platform SAR in single channel squint mode is realized. The validity of the above models and algorithms has been verified by simulation experiments. The results show that the above-mentioned work can be used to realize the high-efficiency and high-precision imaging of the near-space slow-speed platform SAR.
【學(xué)位授予單位】：電子科技大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2014
【分類號(hào)】：TN957.52
，
本文編號(hào)：2451473
[Abstract]:The adjacent space refers to the airspace between 20 km and 200 km from the earth's surface. The air pressure in the bottom region of 20 km to 50 km is relatively low, the disturbance current is stable, and the influence of cloud and rain is free, so it is suitable for flying aircraft such as floating-air slow-speed platform and so on. The synthetic Aperture Radar (SAR), which is carried on the slow platform near the space, has the advantages of long lag time, short revisit period and wide observation area. It has important application value in the fields of reconnaissance and environmental monitoring in sensitive areas. The near-space slow-speed platform SAR has many special problems which are different from spaceborne and airborne radar. It needs to be explored and studied, and it is also a hot research topic in the international radar field in recent years. In this paper, the echo model, imaging mode, imaging algorithm, motion compensation, moving target detection and other core problems of the near-space slow-speed platform SAR are studied theoretically and numerically. The main contents are as follows: 1, The echo model of the near space slow platform SAR is established, and the echo characteristics of range migration, Doppler, range azimuth coupling and space variation are analyzed, which provides the theoretical basis for the study of imaging mode and imaging algorithm. A time division multi-angle common aperture imaging model is proposed, which can effectively utilize the redundant time resources of slow motion to sample the azimuth dislocation of different angle imaging regions, which provides a new solution for fast imaging of large scenes. A compensation method of heading motion error based on non-uniform Fourier transform (NUFFT) is proposed in this paper. The non-uniform samples in time domain are homogenized in frequency domain by scaling factor. It can solve the problem of the widening of the main lobe and the rise of the sidelobe caused by the variation of the velocity along the track of the near-space slow-speed platform. 4. An imaging algorithm based on extended wavenumber domain processing is proposed. By embedding the two-dimensional linearization and devoid processing of the echo two-dimensional spectrum in the wavenumber domain processing, the problem of defocusing and geometric distortion on the outside of the SAR imaging region of the near-space slow-speed platform under the condition of constant acceleration can be solved. A moving target imaging method based on Doppler parameter equalization FrFT is studied in this paper. After range migration correction, the Doppler modulation frequency difference between static and moving targets can be used to separate the echoes of static and moving targets. The moving target imaging of the near space slow platform SAR in single channel squint mode is realized. The validity of the above models and algorithms has been verified by simulation experiments. The results show that the above-mentioned work can be used to realize the high-efficiency and high-precision imaging of the near-space slow-speed platform SAR.
【學(xué)位授予單位】：電子科技大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2014
【分類號(hào)】：TN957.52
，
本文編號(hào)：2451473
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