【摘要】：隨機(jī)粗糙面的電磁散射在微波遙感,目標(biāo)探測與識別領(lǐng)域具有顯著的學(xué)術(shù)價(jià)值和廣泛的應(yīng)用前景,而自然界中的地海面往往是雙層或多層的,因此研究分層粗糙面的電磁散射具有十分重要的應(yīng)用價(jià)值。本文推導(dǎo)了基爾霍夫近似下的一維及二維單層粗糙面的電磁散射及透射,利用射線追蹤方法,研究了一維及二維分層粗糙面的電磁散射,并利用一維分層粗糙面電磁散射理論研究了覆蓋雪層土壤面以及溢油海面的電磁散射。論文介紹了粗糙面的幾何建模,使用線性濾波法模擬了不同統(tǒng)計(jì)參量下的一維粗糙面及二維粗糙面;從簡諧波滿足的亥姆霍茲方程出發(fā),結(jié)合邊界條件,求解了粗糙面的平均散射強(qiáng)度及透射強(qiáng)度,同時(shí)引入基爾霍夫近似,推導(dǎo)了不同極化方式下的散射場及透射場的積分表達(dá)式。將生成的一維粗糙面離散為一系列的線段,在遠(yuǎn)場近似條件下求解了每條線段中點(diǎn)處的平均反射強(qiáng)度和平均透射強(qiáng)度,利用能量守恒定律驗(yàn)證了基爾霍夫方法的正確性,數(shù)值計(jì)算并分析了粗糙面的粗糙度以及介質(zhì)的介電常數(shù)對雙站散射系數(shù)和透射系數(shù)的影響。論文將射線追蹤算法引入到一維分層粗糙面的電磁散射求解當(dāng)中,數(shù)值計(jì)算了波在分層介質(zhì)中傳播的入射點(diǎn)、反射點(diǎn)和透射點(diǎn)的位矢及各點(diǎn)之間的相位差,數(shù)值計(jì)算并分析了平面波入射時(shí)一維分層粗糙面的電磁散射隨中間層及底層介質(zhì)的介電常數(shù),中間層介質(zhì)厚度,粗糙面的粗糙度等的變化。結(jié)合土壤和雪的等效介電常數(shù)及其隨濕度和頻率的變化,數(shù)值計(jì)算并分析了覆有雪層土壤面的電磁散射隨雪層及土壤面的粗糙度,土壤濕度及雪層厚度等的變化;利用修正的PM譜模擬覆有油膜的海面輪廓,考慮油膜厚度及風(fēng)速的變化,對比了不同極化方式下修正海譜與原始海譜的雙站散射,證明了修正海譜的有效性。論文將錐形波引入到基爾霍夫近似下的二維粗糙面散射中,推導(dǎo)了錐形波入射下的二維單層粗糙面電磁散射及透射,將生成的二維粗糙面離散為三角面元,求得每個(gè)面元中點(diǎn)處的散射場及透射場,數(shù)值計(jì)算并分析了均方根高度、相關(guān)長度、介電常數(shù)等對散射系數(shù)及透射系數(shù)的影響。介紹了應(yīng)用于二維分層粗糙面的射線追蹤方法,給出了反射射線、透射射線方向的判定方法,并介紹了一種射線與三角面元的快速相交測試方法�；诜謱哟植诿娴膸缀翁匦�,提出了粗網(wǎng)格細(xì)網(wǎng)格法和可行區(qū)域搜索算法對射線追蹤進(jìn)行加速,數(shù)值計(jì)算并分析二維分層粗糙面的電磁散射隨中間層以及底層介質(zhì)的介電常數(shù),中間介質(zhì)層厚度及粗糙面的粗糙度等的變化。
[Abstract]:Electromagnetic scattering from random rough surfaces is of great academic value and wide application prospect in microwave remote sensing, target detection and recognition. Therefore, the study of electromagnetic scattering from stratified rough surfaces has very important application value. In this paper, the electromagnetic scattering and transmission of one-dimensional and two-dimensional single-layer rough surfaces under Kirchhoff approximation are derived. The electromagnetic scattering of one-dimensional and two-dimensional stratified rough surfaces is studied by means of ray tracing method. Based on the theory of electromagnetic scattering from one-dimensional stratified rough surface, the electromagnetic scattering of snow cover soil and oil spill surface is studied. In this paper, the geometric modeling of rough surface is introduced, and the linear filtering method is used to simulate the one-dimensional rough surface and two-dimensional rough surface under different statistical parameters, starting from the Helmholtz equation satisfied by the simple harmonic, combining with the boundary conditions, The average scattering intensity and transmission intensity of rough surface are solved, and the integral expressions of scattering field and transmission field under different polarization modes are derived by introducing Kirchhoff approximation. The generated one-dimensional rough surface is discretized into a series of line segments, and the mean reflection and transmission intensity at the midpoint of each line segment is solved under the condition of far-field approximation. The validity of Kirchhoff's method is verified by energy conservation law. The effects of roughness of rough surface and dielectric constant on bistatic scattering coefficient and transmission coefficient are numerically calculated and analyzed. In this paper, the ray-tracing algorithm is introduced to solve the electromagnetic scattering of one-dimensional stratified rough surface. The incident point, the potential vector of reflection point and transmission point and the phase difference between each point are numerically calculated. The variation of electromagnetic scattering of one-dimensional stratified rough surface with the dielectric constant, the thickness of the interlayer medium and the roughness of the rough surface are numerically calculated and analyzed when the plane wave is incident. Combined with the equivalent dielectric constant of soil and snow and its variation with moisture and frequency, the variation of electromagnetic scattering from snow covered soil surface with roughness of snow layer and soil surface, soil moisture and snow layer thickness was numerically calculated and analyzed. The modified PM spectrum is used to simulate the sea surface profile with oil film, considering the variation of oil film thickness and wind speed, the bistatic scattering between the modified sea spectrum and the original sea spectrum under different polarization modes is compared, and the effectiveness of the modified sea spectrum is proved. In this paper, the conical wave is introduced into the two-dimensional rough surface scattering under Kirchhoff approximation, and the electromagnetic scattering and transmission of the two-dimensional single-layer rough surface under the incidence of the conical wave are derived. The generated two-dimensional rough surface is discretized into a triangular plane element. The scattering and transmission fields at the midpoint of each plane are obtained. The effects of root mean square height, correlation length and dielectric constant on the scattering and transmission coefficients are numerically calculated and analyzed. The ray tracing method applied to two-dimensional stratified rough surface is introduced. The method of determining the direction of reflected ray and transmission ray is given, and a fast method for measuring the intersection of ray and triangular plane is introduced. Based on the geometric characteristics of layered rough surfaces, a coarse grid fine mesh method and a feasible region search algorithm are proposed to accelerate the ray tracing. The dielectric constants of the two-dimensional layered rough surfaces with the dielectric constant of the intermediate layer and the underlying medium are numerically calculated and analyzed. The variation of the thickness of the intermediate layer and the roughness of the rough surface.
【學(xué)位授予單位】：西安電子科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TN011

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