Study on Electromagnetic Radiation From Printed Circuit Board and Imaging of Its Radiation Sources

不希望的电磁辐射来自构成电气设备的印刷电路板(PCB)或电力线。这项研究的目的之一是相当严格地分析来自印刷电路板的电磁辐射，并估计不需要的辐射的位置。印刷电路板由传输线导线、无源元件、有源元件等组成。电磁辐射主要来自传输线，因为传输线是天线的导体。由于物理现象容易捕捉，因此在时间域中进行分析将是非常有效的，以便估计不需要的辐射。在这一点上，时域有限差分法(FDTD)是最常用的电磁仿真方法。该方法的优点在于它能在实际精度的范围内对电磁场进行简单而高效的建模。然而，当需要一个相当精确的结果时，即使几何形状相对简单，也往往需要大量的计算机资源，该研究提出了一种提高FDTD方法分析介质衬底上平面结构的精度的技术。这种改进是通过在FDTD更新方程中加入准静态场行为来实现的，而准静态场是通过对微带线的瞬变电磁近似而得到的，其形式是封闭的。将改进的FDTD算法应用于微带结构和曲线传输线。数值和实验证明，该方法具有较高的精度和稳定性；另一方面，由于测量设备的动态范围，需要在印刷电路板附近进行不需要的辐射估计。本文对MUSIC算法进行了改进，将其用于近场电磁辐射源的估计。从理论上证实了该方法的有效性。

The undesirable electromagnetic radiation occurs from a printed circuit board (PCB) or power lines which compose an electric equipments. One of the purposes of this study is to analyze the electromagnetic radiation from the PCB quite rigorously, and to estimate the position of the undesirable radiation. The PCB consists of the transmission line conductors, passive elements, active elements and so on. The electromagnetic radiation comes from the transmission lines mainly because the transmission line works as the antenna conductor. In order to estimate the undesirable radiation, the analysis in time domain would be very effective because the physical phenomena are able to catch easily. In this viewpoint, the Finite Difference Time Domain (FDTD) method is die most useful electromagnetic simulation method. The strength of the method is its simplicity and efficiency to model the electromagnetic field within a practical level of the accuracy. However, when one requires a quite accurate result, a great amount of computer resource is often required even if the geometry is relatively simple.This study proposes a technique for improving the accuracy of the FDTD method to analyze the planar structures printed on a dielectric substrate. The improvement is achieved by incorporating a quasi-static field behavior to the FDTD update equations The quasi-static field which is expressed as a closed form is obtained by a TEM approximation of a microstrip line. The modified FDTD algorithm is applied to the microstrip structures and the curved transmission line. It is confirmed numerically and experimentally that the proposed method is highly accurate and stable.On the other hand, the estimation of the undesirable radiation will be done near the PCB because of the dynamic range of the measurement equipment. In this study the MUSIC algorithm was modified to estimate the near field electromagnetic radiation sources. The effectiveness of this method is confirmed theoretically.