Research And Application Of Finite Difference Time Domain Method For Thin Structuers In Electromagnetic Shileding

It is of significant theoretical meaning and practical value to research the coupling mechanism of shield under the operation of the electromagnetic field and to analyze shielding effectiveness of shield. In this thesis, supported by the Scientific Funds for Outstanding Young Scientists of China (Grant No. 50325723) and the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No.20020079003), the finite difference time domain (FDTD) method to analyze the shielding effectiveness of the thin-walled enclosure with apertures and the metal cage is emphatically researched. Compared with the calculated results in the published references and the measuring results, the analytical method, the methods presented in this thesis are proved to be correct. The main innovative achievements are as follows:1. An electromagnetic field numerical method is put forward to analyze shielding effectiveness of the infinite thin conductor and dielectric sheet based on the FDTD. Then, the algorithm of dealing with the difference forms of the components at the edges is given and the electromagnetic field numerical method is put forward to compute shielding effectiveness of enclosure with thin walls based on FDTD. And the developed methods are verified to be valid and correct by comparing the results with those of the analytical method and measurement.2. An electromagnetic field numerical method is proposed to analyze the shielding effectiveness of the thin multi-layer material sheet. And the developed method is verified to be valid and correct by comparing the results with those of the analytical method. Then, the electromagnetic fields in the enclosure coupling by the aperture and penetrating through the wall are compared. And, at some frequency point, the later is larger than the former.3. An electromagnetic field numerical method is presented for the modeling the dispersive sheet. The wave reflected from a coated ideal conductor and the cut off frequency of a waveguide loaded with a dispersive sheet are computated and the result was in agreement with the results of the analytical method and published reference. And, the validity of the presented methods is verified.4. An electromagnetic field numerical method has been put forward is deduced to analyze shielding effectiveness of the cage built with thin metal wire based on FDTD. And the deduced method is verified to be valid by comparing result with the result of the method of moment (MOM).5. Some effects to affect the shielding effectiveness of the enclosure with apertures and the metal cage are analyzed and some valuable rules for engineering are summarized. These effects include the frequency of the incident waves, the size of the aperture, the number of the apertures, the radius of the conductor wire and the size of the mesh of the metal cage.