裸地散射特性分析

地物环境特性差异是不同地物之间散射特性差异的主要因素,本文针对不同地物散射特性差异影响因素难以量化的难题,利用车载微波散射计和环境参数测试系统开展以玉米、大豆、胡萝卜及裸地等多种不同地物为对象的散射特性对比试验,研究了不同地物之间的散射特性差异,以及其生长状态的改变对散射特性的影响,并建立了一种关联环境参数的地物散射模型;利用单类型多地物散射系数估算了大区域复合地物散射系数,与实测数据对比误差小于4 dB,说明了推算方法的有效性,也为复杂场景地杂波预测研究提供了支撑。

     

相邻目标电磁散射特性的研究

本文研究了植被环境中相邻两目标的电磁散射问题.在互易原理的基础上,得到了计入相邻目标二次散射的散射场的积分表达式.推导得出了相邻有限长导体圆柱的二次散射场的闭式解,分析计算了其前向散射特性,并与矩量法的数值结果进行了比较.     

基于探地模型的目标散射特性研究

以不同情况下的地埋目标散射特性为前提,能够准确地从探地雷达图像中提取目标体的结构信息。使用CST仿真软件上的时域求解器构建频率范围在0.5～3.5 GHz的脉冲体制探地雷达系统的目标散射仿真模型,并对不同传播介质、不同目标体与不同埋藏深度的地埋目标散射特性进行电磁仿真模拟,预演了多种情况下探地雷达系统的探测过程。通过比较不同情况下探地模型的目标回波信号,得出结论：土壤含水会使地面反射增强,目标回波衰减不易识别;目标的尺寸改变对回波幅度有影响,对波形影响不大;当目标材质的电参数改变时,目标体回波波形变化明显;当目标与传播介质的电参数相差较大时,目标回波明显;随着目标埋深增加,目标体回波在时域上向后延迟,可以根据回波时间差计算目标体埋深。通过对仿真结果的分析证明该方法可靠有效,并且仿真过程简便,适用于不同情况下探地雷达的目标散射模拟。     

雷达目标双基地散射特性研究进展

随着同步技术和高性能计算的发展,双/多基地雷达的\"四抗\"优势逐渐得以实现,双/多基地雷达成为当今雷达领域关注的焦点.雷达目标的双基地散射截面积(RCS)、双基地散射中心、双基地极化等特性与目标单基地散射特性相比,具有显著的差异.只有深刻理解雷达目标双基地散射特性才能充分挖掘双/多基地雷达在目标检测、特征提取与识别方面的...     

球形粒子的散射特性分析

在Mie散射和瑞利散射理论的基础上 ,模拟了单个粒子的散射图象 ,然后对粒子的散射光强进行了讨论。介绍了粒子的多次散射理论研究动态 ,建立了多次散射的传输方程     

GPS海面散射信号探测技术研究

该文简述了利用GPS散射信号进行微波遥感的背景和优点,并从GPS海面散射信号极化特性、信号波动情况、波程差引起散射信号相对直射信号的码延迟以及由于海面粗糙度引起的散射信号相关功率扩散几个方面详细分析了海面散射GPS信号检测技术。给出了自行研制的延迟映射接收机的工作原理, 在天津近海进行了首次搭载飞行试验,数据分析结果与理论分析符合。     

FD—TD法分析埋地目标对基带脉冲波的电磁散射特性

本文利用ＦＤ－ＴＤ法分析了埋了埋地目标对基带脉冲波的电磁散射问题。在推出有耗媒质中ＦＤ－ＴＤ法代公式和吸收边办条件的基础上,对基带脉冲波在有耗媒质中的传播特性和埋地目标的电磁散射特性分别进行了较为详细地讨论。给出了部分目标的回波堆积图,并对探地雷达的探测性能与媒质特性、目标特性的关系进行了分析。     

二维目标电磁散射瞬态响应的TLM方法模拟

运用传输线矩阵方法研究二维特殊形状理想导体目标对电磁波的瞬态响应，数值结果表明，ＴＬＭ方法对于电磁散射问题的数值模拟不仅很方便而且实用，尤其对于较为复杂的目标（形状特殊，成分复杂），方法本身不需作任何改变，只需改变网格划分便可以进行计算。     

血小板的光散射特性

利用激光散射法对健康人血小板的光散射特性进行了研究。测量了不同浓度下这种细胞的散射光强和透射光强,并给出了相应的散射系数。     

陆基散射计使用脉冲信号进行后向散射系数的测量和计算

本文提出了开展星地一体化测量的必要性以及与SAR预测条件一致的陆基微波测量系统-脉冲制陆基散射计,分析了使用窄脉冲作为测量信号的测量条件对提高σ∧0的测量和计算方法并推导了相应的计算公式。     

植被散射实验数据的特性分析

本文根据电波所获取的各种樾 射实测数据，分析了它们对不同极化波的响应特性。     

蒙特卡罗方法在小麦后向电磁散射中的应用

本文运用Ｍｏｎｔｅ—Ｃａｒｌｏ方法对小麦的后向电磁散射问题进行了数值模拟。Ｍｏｎｔｅ—Ｃａｒｌｏ方法把电磁波与植被的相互作用看作是光子与离散散射体的连续碰撞，给碰撞赋予概率意义，以此模拟光子的轨迹。小麦被模化成充满半空间的具有一定空间取向及大小的椭圆盘。数值结果与实验数据吻合较好。     

电磁导弹的散射研究

本文讨论能量按r~(-e)衰减的电磁导弹在理想金属椭圆柱和金属球上的散射特性,研究结果表明椭圆柱和金属球对电磁导弹的散射场能量衰减速率分别正比于r~(-(1+e))和r~(-2(2+))。     

铍离子注入锑化铟快速热退火的背散射沟道分析

本文借助背散射沟道分析技术系统地研究了Be离子注入InSb快速热退火后的剩余损伤,采用俄歇电子能谱仪分析了InSb表层组分的化学配比,并对背散射分析的结果进行了详细的讨论。     

Effect of Surface Profile Length on the Backscattering Coefficients of Bare Surfaces

The root mean square (rms) height s and autocorrelation length l are commonly used as the surface roughness input parameters to surface scattering models. Whereas it is well known that the surface roughness parameters of a natural soil surface are underestimated with a short surface profile, it is not clear how much the underestimated surface parameters affect the backscattering coefficients of the surface for various incidence angles and polarizations. In this paper, the backscattering coefficients of simulated and measured surface profiles are computed using the integral equation method and analyzed to answer this question. A 4000lmacr-long rough surface is generated numerically, where lmacr is the true correlation length of the surface, and the backscattering coefficients of the surface are computed and analyzed for various conditions. The rms error of the backscattering coefficient at a medium range of incidence angles is less than 1.5 dB for vv-polarization and 0.5 dB for hh-polarization if the profile length is larger than 5lmacr for a surface with ks=1.0, kl=10.0, and epsiv _r=(10.0,2.0). Similar results are obtained from numerous simulations with various roughness conditions and various wavelengths. It is also shown that the rms error of the backscattering coefficients between 5- and 1-m-long measured surface profiles is 1.7 dB for vv-polarization and 0.5 dB for hh-polarization at a medium range of incidence angle (15deglesthetasles70deg), whereas the surface roughness parameters are significantly reduced from 2.4 to 1.5 cm for the rms height s and from 35.1 to 10.0 cm for the autocorrelation length l     

Microwave Emission from Smooth Bare Fields and Soil Moisture Sampling Depth

This paper studies the depth to which soil moisture can be directly estimated with microwave measurements over smooth bare fields. The analyses are based on both theoretical and experimental considerations at the frequencies of 1.4, 5.0, and 10.7 GHz. Radiative transfer calculations of microwave emissivities at these frequencies are performed with a number of moisture profiles measured for two soils. The calculated emissivities are compared with those derived from the Fresnel equation to deduce the microwave sampling depth in soils. The data acquired from the ground-level radiometric measurements during the summers of 1979-1981 are examined and compared with the theoretical retical analysis. Both theoretical and experimental analyses lead to the conclusion that the microwave sampling depth in soils is about one tenth of the wavelength of observation. It is shown that the moisture content at any depth near the surface of a smooth soil can be estimated, in principle, by a combination of a radiometric measurement and a curve generated by the Fresnel equation at an appropriate frequency, provided that the texture of the soil is known.     

水稻,小麦后向散射特性的实验研究

对１９９０和１９９１年用Ｘ波段散射计测量的水稻和小麦后向散射系数在植物生长过程中随地物参数变化的结果进行了分析。结果表明：①Ｕｌａｂｒ对矮杆植被给出的经验模型与实验结果一致。②在水稻对微波的后向散射中，地面散射占主要部分。其后向散射系数可用植被参数Ｈ·Ｗ的线性模型来拟合。③由于麦田土壤含水量低，小麦后向散射系数一般比水稻低６ｄｂ左右。测量结果显示，在１８°入射角附近，小麦后向散射系数对土壤含水量较灵敏。在小麦生长过程中，测量的后向散射系数没有显示出明显的随生长期的规律性变化。     

Backscattering of the electromagnetic missile from an irregularsurface

The scattering of an electromagnetic missile (EMM) with energy decreasing as r^-4 from a perfectly conducting irregular surface is analyzed. The mean scattered power is derived. It is shown that the rate of the average energy decay for the backscattering field far from the irregular surface is proportional to r^-4, which is the same as that for plate scattering     

双频多极化SAR测量深层土壤湿度

该文提出了利用由矢量网络分析仪构造的VHF/UHF双频、多极化合成孔径雷达(SAR)测量深层土壤湿度的方法;给出植被后向散射机理、深层土壤后向散射机理,土壤介电常数模型;对裸露土壤深层后向散射、土壤介电特性给出仿真结果。通过已知的单层土壤(双层介质粗糙面模型)的后向散射验证了模型的正确性。     

Calculations of the Microwave Brightness Temperature of Rough Soil Surfaces: Bare Field

A model for simulating the remotely sensed microwave brightness temperatures of soils with rough surfaces is developed. The surface emissivity of the soil media is calculated from one minus its reflectivity, which is obtained by the integration of the bistatic scattering coefficients for rough soil surfaces. The soil brightness temperature is obtained from the product of the surface emissivity and the effective soil temperature, which is calculated with measured soil moisture profiles and soil temperature profiles at various soil depths. The roughness of a soil surface is characterized by two parameters, the surface height standard deviation a and its horizontal correlation length l. The model calculations are compared to the measured angular variations of the polarized brightness temperatures at both L-band (1.4 GHz) and C-band (5 GHz) frequencies. A nonlinear least squares fitting method is used to match the model calculations with the data, and the best fit results produce the parameter values of a and l that best characterize the surface roughness. The effect of rough surface shadowing is also incorporated into the model by introducing a shadowing function S(?), which represents the probability that a point on a rough surface is not shadowed by other parts of the surface. The model results for horizontal polarization are in excellent agreement with the data, both qualitatively and quantitatively. For vertical polarization, some discrepancies exist between the calculations and data. Possible causes of the discrepancy are discussed.