| Today, the information technology is growing fast, the electromagnetic problems become more and more serious. And the electromagnetic interference works on the equipment of the electronic system is more and more serious, too. Now. it is necessary to consider the working order of the electronic system when it’s under the electromagnetic interference in the analysis and design of modern electronic system. Normally, in order to protect the electronic system from the electromagnetic interference, electronic system is usually required to be installed in the shutter. However, for the ventilation and heat dissipation and so on. it is inevitable to make some tiny apertures on the shielding wall. Therefor, the external electromagnetic interference is coupled with the electronic system through the apertures by apertures coupling, inductance coupling and other ways. So it is difficult to calculate the response of the electronic system with the general classical algorithm. So in 1974, C.E.Baum and F.M.Tesche proposed how to use the electromagnetic topology method in analyzing the problem of the interaction of electronic system and electromagnetic wave. On this basis, they proposed the concept of the electromagnetic topology which was a effective way to study and solute the problem of electromagnetic interference and coupling of the electronic system worked under the external electromagnetic waves. After thar, C.E.Baum and other peoper proposed the BLT equation which was used to solve the electromagnetic interferce problems. It is proved that the electromagnetic topology methed was efficient to solve the problems of electromagnetic interference and electromagnetic coupling when a complex electronic system under the electromagnetic environment.First, the background and the development of the electromagnetic topology are describedr. And this paper deducts the BLT equation in detail, which is proposed by C.E.Baum, T.K.Liu and F.M.Tesche, and introduces the different kinds of equations under different excitation sources systematically. Then we analyze the terminal response of one transmission line excited by the external electromagnetic field, which is behind a shielding wall with multi-apertures, make the electromagnetic topology model and solve the BLT equation. In addition, the terminal response of transmission line is analyzed when the number, the size and the location of apertures are changed. Finally, the shielding effectiveness of single-shielded cavity and double-shielded cavity is analyzed. At the same time, the model of a transmission line in double-layer shielding cavity with apertures is analyzed. In the analysis of the model that the inner transmission line is interfered by external electromagnetic field.the external cavity is calculated by transmission line model. And the internal cavity is dealed with the electromagnetic topology theory. So a method to computed the terminal response of transmission line in double-layer shielding cavity with apertures is proposed which is based on TL+BLT model. |
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