Study Of Common-mode Radiation Theory In EMC About Metal Cases

Many metal cases connecting with cables cause the question of common-mode radiation that becomes the important obstacle that many electron equipments don't pass the electromagnetic compatibility test. It is very important to analyze characteristic of electromagnetic compatibility in the environment existing many perfect conductors connecting with cables. To solve this question, firstly, the experiment is done to observe the common-mode radiation phenomena of switching power supplies impersonally and to analyze interfering sources and coupling paths of common-mode radiation. Then, the current distribution from the folded antenna, the quadrate loop antenna and the loop antenna loaded by capacitance is analyzed using MoM after modeling. Further, the radiation field of short circuit and open circuit loop antennas with different frequencies is studied. Finally, electric field integral function (EFIE) and method of moment (MoM) are used to solve the question of connecting arbitrary shape cables with arbitrary shape metal cases, and the triangular model (RWG basis function) is applied in the metal case part, the juncture part adopts Costa basis function and the pulse basis function is applied in the wire part. These works above obtain some valuable conclusions, which can guide common-mode radiation question with connection metal cases and ground for studying electromagnetic compatibility in the complex environment in future.