| Summary: | 碩士 === 國防大學中正理工學院 === 軍事工程研究所 === 93 === This study investigates the shielding effectiveness (SE) of the outer wall of military facilities by means of the theoretical and numerical methods. The formula of SE was first developed by the theoretical method, and then the factors affecting the SE characteristics of cement mortar and concrete were sequentially analyzed. The factors are such as thickness, conductivity of the shielding layer and incidence angle of the electromagnetic wave. The results show that the SE of the shields increases as the thickness and conductivity increase respectively and the latter is more outstanding. As the part of incident angle, the SE increases with angle in perpendicular polarization. When the angle is between 70 and 80 degree in parallel polarization, the SE is the worst. The angle of the worst SE is similar with normal incidence. As a result, the SE of normal incidence can be taken for reference in analysis. As desiring, the non-planar shields can increase proportion of oblique incidence and the SE can be raised.
The Finite Difference Time Domain method (FDTD) was adopted the numerical method. The effects of the concrete and coating thin materials with high conductivity on the SE were further discussed. It shows that the SE increases up to 33 dB (132%) for the shielding with the interval size of 40~60 mm and the ratio of thickness of 1:1.
Finally, the results of this study can be developed the concept and method of applying in based electromagnetic protection of military facilities. For present military facilities, it can improve the protective ability by coating thin materials with high conductivity in surface of both sides. As newly ones, it can improve protective ability by the design of non-continuous interval and coating thin materials with high conductivity in surface of both sides.
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