Analysis On Shielding Effectiveness Of Perforated Metal Cavity With The Modal Method Of Moments

In recent years, electromagnetic compatibility (EMC) problems of electronicsystems are more and more serious, and the study of electromagnetic compatibility isbeing more and more attention. As is well-known, electromagnetic shielding is a veryimportant part of electromagnetic compatibility. In this area, metallic enclosures arefrequently used to improve immunity of sensitive systems or block EM emission fromelectronic equipments. Shielding effectiveness (SE) is de ned for a shielding enclosureto show its ability to hinder EM elds. However, most of the metal cavity has aperturesdue to the input and output connections, heat dissipation. And the apertures largely affectthe performance of shielding cavity.In the paper, modal method of moments is the main method to calculate theshielding effectiveness of a perforated rectangular cavity and double-layer shieldingenclosure.First, we consider two cases for a single rectangular cavity according to the size andlocation of the aperture on the cavity, and introducing the induction current of a cavitysurface to make the result accurate when metal cavity with larger aperture or metal cavitywith aperture near to the edge. For the thickness of the cavity, the cavity with apertures isdivided into three areas: the outer space regions I, apertures region II, the chamberinterior region III. We can get electric field integral equation and magnetic field integralequation for electric field on the cavity surface in a normal direction is zero and thecharacteristics of continuous magnetic field on the aperture surfaces. Solution of theintegral equation can get the shielding effectiveness of cavity.Then, the solving process of the modal method of moments in a single rectangularcavity is applied to the double-layer shielding model. And the double-layer shieldingcavity is also divided into three regions: outer space area I, fist cavity area II, secondcavity area III. Shielding effectiveness can be computed according to the Green’sfunction of each area and magnetic field integral equation.Finally, the method in the paper is suitable to compute shielding effectiveness for a variety of cases by the comparison of theoretical analysis and the data of CST simulationsoftware. Also，the applicability of the method is very strong.