Two important issues must be considered when modeling the terahertz (THz) wave scattering behavior using microwave EM methods. The first is the material response characteristics, including the metallic materials that may be beyond the scope of the Drude model's description and the dielectric materials that may lack appropriate description models. The second is the modeling method for investigating the THz scattering behavior of the surface random roughness and the complex fine structures. Several theoretical endeavors are presented in this paper to elucidate the surface- and volume-scattering phenomenon observed in the experiment data. First, we employ the Integral Equation Method (IEM) to fit the measured data of an aluminum plate. Good agreements confirm the superior applicability of IEM to the metallic materials. Nevertheless, for dielectric materials, the volume-scattering contributions of the inner microstructures or particles whose sizes are comparable to the THz wavelength are required to be considered. Furthermore, our findings state that, for dielectric materials, it can be fit to the experimental data with the help of the Vector Radiative Transfer (VRT) theory. Finally, this research proposes a semi-deterministic description-based ray-tracing high-frequency algorithm to realize the rapid modeling of the coherent and incoherent scattering of electrically large complex targets at THz bands.%微波方法到太赫兹散射特性建模的延拓面临两个关键的科学问题研究,其一是材料响应特性延拓,包括金属属性向合金属性过渡导致Drude模型无法准确描述,以及介质材料在太赫兹频段的响应模型研究;其二是表面随机粗糙结构、以及复杂细微精细结构在太赫兹频段下的散射行为建模方法的延拓研究.微波频段下可视同为光滑的金属表面在太赫兹频段可能呈现出表面微粗糙特性.此外,针对含介质涂覆或全介质表面太赫兹散射特性的建模,需要结合随机边界散射理论,建立多层描述模型,以涵盖其中的面散射和体散射现象.该文首先采用积分方程方法描述和分析了金属粗糙表面的太赫兹散射规律,与实测数据吻合较好.其次,对于含涂覆或介质材料的目标表面,除表面粗糙的影响外,材料内部的微小粒子成分(如碳粉、石墨、金属粉等)的电尺寸与太赫兹波长相比拟,实验显示其体散射贡献不可忽视.该文尝试用矢量辐射传输理论与积分方程方法结合的多层模型来描述含介质材料表面的散射特性,很好地解释了实测规律.最后,该文提出基于"半确定性"描述的射线追踪高频算法,实现了复杂目标表面相干和非相干散射特性的一体化快速建模,为超电大复杂目标太赫兹散射特性的建模分析提供有效手段.
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