【摘要】：星載合成孔徑雷達(dá)(Synthetic Aperture Radar,SAR)可全天時(shí)、全天候獲取大范圍、高分辨圖像,在軍事偵察和經(jīng)濟(jì)建設(shè)中有著重要的應(yīng)用價(jià)值。相對(duì)于高頻段SAR而言,P波段SAR一方面具有更強(qiáng)的穿透性,可穿透地表和植被成像,是發(fā)現(xiàn)和探測(cè)被淺地表、植被、冰雪等覆蓋的隱蔽目標(biāo)的有效手段;另一方面,P波段SAR對(duì)生物量更為敏感,可對(duì)森林生物總量進(jìn)行高精度測(cè)量。因此,星載P波段SAR兼具P波段SAR穿透能力強(qiáng)、對(duì)生物量敏感的特點(diǎn)和星載SAR大范圍觀測(cè)的優(yōu)勢(shì),在隱蔽軍事目標(biāo)偵察、生物量統(tǒng)計(jì)、冰層結(jié)構(gòu)探測(cè)等方面具有廣闊的應(yīng)用前景。然而,星載P波段SAR受到電離層色散、閃爍、法拉第旋轉(zhuǎn)(Faraday Rotation,FR)等傳播效應(yīng)的嚴(yán)重影響,成為系統(tǒng)發(fā)展的瓶頸之一。本文緊緊圍繞“星載P波段SAR電離層效應(yīng)”這一關(guān)鍵問題,針對(duì)“電離層傳播效應(yīng)建模仿真”、“電離層效應(yīng)影響分析”以及“電離層效應(yīng)校正”等三個(gè)方面展開了系統(tǒng)性研究。本文主要工作包括:第二章介紹了電離層電波傳播效應(yīng)。首先,從電離層折射指數(shù)及其電子密度分布兩個(gè)方面闡述了電離層色散、隨機(jī)、各向異性的介質(zhì)特性。其次,以麥克斯韋方程組為出發(fā)點(diǎn),推導(dǎo)了背景電離層對(duì)電磁波的色散和FR效應(yīng)的影響機(jī)理,以相位屏理論為例介紹了電離層的閃爍理論。第三章研究了基于電離層多相位屏理論的星載SAR信號(hào)建模與仿真。針對(duì)當(dāng)前普遍采用的單相位屏理論只適用于弱閃爍情況的局限性,將多相位屏理論應(yīng)用于星載SAR電離層效應(yīng)模擬中,解決了星載SAR電離層強(qiáng)閃爍效應(yīng)模擬問題。針對(duì)星載SAR信號(hào)的斜入射傳播幾何,通過求解拋物方程,得到了電磁波斜入射情況下的衍射結(jié)果,并將其擴(kuò)展到了球面波情形。在此基礎(chǔ)上,設(shè)計(jì)并實(shí)現(xiàn)了星載P波段SAR電離層效應(yīng)仿真軟件。第四章基于沖激響應(yīng)矩陣模型分析了電離層對(duì)星載P波段SAR的影響。首先,統(tǒng)一建立了電離層效應(yīng)對(duì)星載SAR的影響模型,將色散、閃爍及FR效應(yīng)包含在星載極化SAR系統(tǒng)沖激響應(yīng)矩陣中。然后,基于新模型研究了電離層的色散、閃爍和FR效應(yīng)對(duì)星載P波段SAR的影響:提出了利用電離層非線性相位誤差大小判斷色散效應(yīng)對(duì)SAR距離壓縮性能影響的方法,該方法降低了對(duì)數(shù)值仿真的依賴性,簡(jiǎn)化了分析過程;分析了閃爍效應(yīng)影響下的SAR方位壓縮性能與電離層不規(guī)則體之間的關(guān)系,數(shù)值仿真驗(yàn)證了分析結(jié)果的正確性;分析了電離層FR效應(yīng)的色散特性及其對(duì)星載極化SAR系統(tǒng)成像性能的影響。第五章研究了星載SAR電離層效應(yīng)校正方法。提出了基于譜分割的電離層路徑電子總量(Total Electron Contents,TEC)估計(jì)方法以校正色散效應(yīng),該方法不需要電離層TEC外部測(cè)量數(shù)據(jù)的輔助,可以實(shí)現(xiàn)SAR數(shù)據(jù)電離層色散效應(yīng)的自校正;指出了相位梯度自聚焦方法的信號(hào)模型與電離層閃爍效應(yīng)信號(hào)模型的聯(lián)系,分析了并驗(yàn)證了該方法校正閃爍效應(yīng)的適用性;提出了一種基于極化協(xié)方差矩陣的法拉第旋轉(zhuǎn)角估計(jì)新方法,與現(xiàn)有方法相比,新方法在系統(tǒng)相位不平衡影響具有更小的均方根誤差,且誤差大小幾乎與法拉第旋轉(zhuǎn)角真值無關(guān)。仿真實(shí)驗(yàn)及PALSAR實(shí)測(cè)數(shù)據(jù)處理驗(yàn)證了上述校正方法的有效性。
[Abstract]:The star-borne synthetic aperture radar (SAR) can acquire large-range and high-resolution images all day, and has important application value in military reconnaissance and economic construction. Compared with the high-band SAR, the P-band SAR has stronger penetration, can penetrate the surface and the vegetation, and is an effective means of finding and detecting the hidden target covered by the shallow surface, the vegetation, the ice and snow, and the like; on the other hand, the P-band SAR is more sensitive to the biomass, and high-precision measurement can be carried out on the total amount of the forest biomass. Therefore, the star-borne P-band SAR has the advantages of strong penetration ability of the P-band SAR, the characteristics of the biomass-sensitive characteristics and the wide-range observation of the satellite-borne SAR, and has wide application prospect in the aspects of covert military target reconnaissance, biomass statistics, ice-layer structure detection and the like. However, the star-borne P-band SAR is seriously affected by the propagation effects such as ionospheric dispersion, flicker, Faraday rotation (FR), and becomes one of the bottlenecks in the development of the system. This paper focuses on the key problem of the 鈥淭he Ionospheric Effect of the Star-borne P-band SAR鈥，

本文編號(hào)：2360192