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

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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.