太赫兹与远红外频段下铝质目标电磁特性与计算*

摘要

在太赫兹与远红外频段，铝处于由导体到介质的过渡，研究该频段铝质目标与电磁波的相互作用机理对于实现太赫兹频段目标精确电磁散射计算具有重要意义。基于实验测量数据，设计有效误差准则模型拟合得到了太赫兹与远红外频段铝的介电系数模型；基于拟合模型通过推导过渡阶段不同损耗机理下铝中传播电磁波的空间相位系数与铝的波阻抗等参数，分析了太赫兹与远红外频段电磁波在铝中的透射与反射特性，给出了铝的反射率关于频率的变化曲线。结果表明铝中电磁波传播参数从微波向太赫兹频段过渡时具有很好的连续性与一致性；基于阻抗边界条件的雷达散射截面计算结果表明太赫兹频段光滑铝质目标可视做理想导体进行计算，太赫兹雷达散射截面测量中可利用光滑铝板或铝球做为定标体。%In the terahertz and far infrared region, aluminum is in a state of transition from conductor to dielectric, and the research of the interaction between aluminous target and electromagnetic wave is meaningful for scattering prediction of targets. With the available error criterion model, dielectric function of aluminum is determined by fitting to experimental data in the terahertz and far infrared region. The transmitted parameters in aluminum are deduced by considering different loss mechanisms. Reflection and transmission characteristics on the interface of aluminum are investigated, and the reflection coefficients are given as a function of frequency. Results show that the transmitted parameters in aluminum keep their continuity and coherency from microwave to terahertz frequency. RCS (radar cross-section) results of aluminum plates computed by IBC method demonstrate that the increased wave impedance of aluminous targets has little impact on its backscattering, and the polished aluminous plate or sphere can still be treated as a perfect electrical conductor and used as a reference for RCS calibration.