【作者】 汪彤；

【导师】 张文俊；

【作者基本信息】 上海大学 ， 电磁场与微波技术， 2001， 博士

【摘要】 自然界中绝大部分物质属于色散媒质，研究和了解色散媒质的宽频特性对推动现代通信与信息技术、生物电子科学、材料科学和空间技术等领域的科技发展及应用具有非常重要的意义。而由于色散媒质特性的复杂性，其瞬态电磁特性研究作为电磁学领域的前沿研究课题之一，历来是电磁研究中的难题，至今尚未得到很好的解决。本文着重在数学模型建立和色散媒质瞬态电磁特性研究两方面进行研究工作： 首先，本文基于数字信号处理技术建立和完善新的适用于色散媒质瞬态电磁特性研究的时域有限差分法((FD)~2TD)，以提高其有效性和普适性。基于对数字滤波器频响特性和媒质色散特性相似性的考虑，提出了采用无限冲激响应滤波器(ⅡR)模拟色散媒质特性的新思路。在此基础上，结合数字信号处理给出了基于复介电常数的(FD)~2TD-PF法和基于电导率的(FD)~2TD-CF法。并对新算法的数值色散关系、稳定性条件和适用范围等进行深入研究。另外借助MATLAB数值软件包及其提供的数字信号处理工具，对新算法进行改进和完善。 第二，在(FD)~2TD法中引入离散时间系统的概念，建立了新的适用于任意色散媒质的吸收边界条件，并对其吸收效果及稳定性条件进行了研究。 第三，利用所建立的新数学模型与方法对色散媒质的瞬态电磁特性及其作用机理进行分析与研究。运用新的(FD)~2TD算法和2001年上海大学博士学位论文小波变换对色散媒质的瞬态电磁传播特性进行系统研究与分析，尤其是分析与比较各类色散媒质电参量对瞬态电磁波传播特性的影响。并且以典型色散媒质为例，对不同形状色散目标及多层色散媒质柱体目标的时域散射特性进行数值模拟与分析.通过对简化色散媒质模型进行时域散射测量，与数值结果进行对比。研究表明色散媒质材质的影响在瞬态电磁波的传播及散射中具有一致的反映，主要体现在物体瞬态电磁的后期响应;目标的几何信息则主要体现在早期响应中。 最后，简要论述了目标识别的方法，讨论色散媒质的瞬态特性研究对目标识别的意义和作用。为开拓瞬态电磁场应用的新方法与新技术，特别是色散目标识别新技术，提供必要的理论基础与依据。更多还原

【Abstract】 It is of great importance to study the transient electromagnetic characteristics of dispersive media owing to its promotive effects in many fields of engineering interest. However, due to the complexity of the dispersive media, the study of the transient electromagnetic characteristics, the leading research in the electromagnetic field, remains one of the unsolved problems. In this paper attention is paid to the model theories of transient electromagnetic problems of dispersive media and the study of the transient electromagnetic characteristics.Firstly, based on the digital signal processing, a new frequency-dependent finite-difference time-domain ((FD)2TD) method for arbitrary dispersive media is established and improved. The validity of the new numerical method is improved and the application is extended to dispersive media. The dispersion of media is modeled with the infinite-impulsive response filters (IIR). In this paper two (FD)2TD methods based on the permittivity or conductivity are proposed and their numerical dispersion, stability and applicability are also studied.Secondly, based on the concepts of discrete system a new absorbing boundary condition for arbitrary dispersive media is derived. Its stability and efficiency are also studied.Thirdly, the transient electromagnetic problems of dispersive media are simulated and studied with the new (FD)2TD method builtin this paper. The propagation and scattering characteristics of dispersive media are studied in-depth in time-domain. The (FD)2TD method and Wavlet transform are applied to analyze the transient propagation in dispersive media. The scattering of several objects with different shape and complex objects formed with multi-layer dispersive media are simulated. The simple experiment models for dispersive media are built and the measurement results are compared to the numerical solutions. It is shown that the media information is indicated in the late-time response of the transient response, while the geometry information is indicated in the early-time response.Finally, the method of object identification including the significance of the research in this paper is discussed briefly. The research in this paper has laid a foundation for the object identification.更多还原