Study On Simulation Of Electromagnetic Radiation Through Apertures Or Slots In Conducting Enclosure

Electromagnetic compatibility (EMC) in modern electrical engineering has becomemore and more important to the designers and the researchers with the wide application ofall kinds of electronic circuits and power electronics technologies. In EMC design toequipment and system, metallic enclosure is widely used to shield from EMI. Because ofthe needs for such various reasons as input and output connections, ventilation panels, etc,the apertures or slots inevitably exist on the conducting shield. These apertures or slots arethe main factor to influence the shielding performance of system. So understanding theintensity and the feature of the electromagnetic field produced by scattering andtransmitting through the apertures is very important for EMC design, that is, thereasonable EMC forecasting must be done before EMC design.Among the existing numerical computation techniques to deal with electromagneticfield, the finite difference time domain (FDTD) method is developed rapidly and usedwidely. At present, FDTD method is one of the main mathematical tools to do EMCforecasting. The FDTD method is studied in this dissertation. FDTD method is analyzedand the difference equations are given. Mur and perfect matched layer (PML) absorbingboundary conditions (ABCs) are studied, and the absorbing performance of both theABCs are compared by numerical tests. The equivalence principle is introduced toextrapolate the far field from the near field.The excitation models of for the simulation of the radiation from enclosure are set upand several thin slot algorithms are deduced and analyzed. The numerical model forenclosure radiation is set up.â‘ The technologies of excitation in FDTD applications are studied and numericalmodel of dipole are set up. The half-analytical numerical equations are deduced to modelthe thin wire antennas and therein the algorithm for modeling antenna feed is proposedbased on the FDTD models of lumped elements.â‘¡The thin slot algorithms in FDTD applications are studied. The capacitive thinslot formalism is given and three-dimensional thin slot algorithm is deduced from contourpath method. After that, a new thin slot modeling method is presented base on Babinet'slaw. Their performance is studied and compared by numerical tests.â‘¢The program for FDTD calculation is designed and is verified by the simulationto an electrical dipole in free space. The model set up for the study on radiation fromenclosure with slots or apertures are validated by the experimental results published in ofother's dissertation. The electromagnetic radiation from the metallic enclosure with apertures or slotsexcited by electrical dipole or doublet antenna are studied and analyzed: the influence ofthe enclosure dimensions, the internal structure and the direction of thin slot on theradiated field; the approximate relation between the far field intensity and the area ornumber of the small hole for the enclosure with multiple holes. All these study work andachievements provide the groundwork for the EMC design of conducting enclosure orsystem.