Radiated emission determination from near field measurements for EMI evaluation of switch mode power supplies components by method of moments

Currently most of the electrical and electronic equipments use switching mode power supplies (SMPS) as their input power source. SMPS increase power - volume ratio using high switching frequencies which it cause producing sever radiated and conducted electromagnetic interference (EMI) in the environment. Therefore, SMPS must satisfy the requirements of electromagnetic compatibility (EMC) standards. Since EMC standard tests are expensive and time consuming, designers are looking to find a way to estimate radiated and conducted emission of SMPS. In this paper we proposed a combined method of moment (MOM) and near field measurement method for efficient simulation of SMPS components radiated emission. The first step of this approach is measurement of electromagnetic field at an arbitrary rectangular plan in the near field (NF) of the board. In the second step, we used MOM to identify the equivalent sources current in the surface of SMPS board based on the NF measurements. In the third step we can estimate the electromagnetic fields at any distance using MOM to evaluate the compliance with regulations. The efficiency of this approach is evaluated for a small electrical dipole and an inductor as a basic component of SMPS.