Study On Suppression Of Aperture-Cavity Resonance By Means Of Absorbing Materials

With the rapid development of science and technology, the use of electronic equipments is growing year by year. However, EMI (Electromagnetic Interference) problem become more and more severe due to electromagnetic radiation produced by electronic equipments. electro-magnetic shielding is an effective way to the solution of EMC(Electromagnetic compatibility) problem of system. , The mechanisms of electro-magnetic shielding is that good conductors have the function of reflecting electromagnetic energy. But in this case, the inner electromagnetic fields of some area in the rectangular cavity will be enhanced, which is called cavity resonant phenomena.In order to solve the slot-aperture cavity resonance, a new approach of putting absorbing material sheet on the wall inside the cavity is introduced. Absorbing Materials refers to the attenuation and absorption of the incident electromagnetic wave energy, and converting the electromagnetic energy to the other forms of energy through the dielectric loss. it can suppress the cavity resonance, increase the shielding effect, decrease the electromagnetic radiation emission and weaken the electromagnetic interference of various parts of the system.. The main contributions of this dissertation are proposed below.1. This thesis first introduces the cavity resonance frequency and the field intensity distribution, then analyzes the mechanism of aperture-cavity resonance by using a generalized network formulation and simulates it basing on HFSS, meantime, a conjunction of lossy character of absorbing material and suppression condition is given.2. The absorbing mechanism, performance and parameters of the absorbing material are introduced. Then the reflecting coefficient of absorbing material is deduced from circuit theory.3. In order to detect the affecting of the absorbing material to the resonant parameters of cavity, the perturbation method is applied. And then the application of finite element method to analyze the slot-aperture cavity resonance with complex boundary condition and complex material fillings is discussed.4. A detailed modeling process based on powerful commercial software is given. then a lots of numerical simulations for absorbing material with different size, types, parameters and position are proposed to present the its suppressing effect for cavity resonance, finally with different slot- apertures and different electromagnetic interference sources, the radiation emission and the shielding effect of cavity coated with absorbing material are studied also. And Some Basic principles of how to apply absorbing material to decay the resonance of slot-aperture cavity are proposed...