Analytical Methods for Evaluating the Characteristics of Noise Suppression Sheets

Noise suppression sheets (NSS) composed of magnetic materials are widely used to mitigate the electromagnetic (EM) emission of radiation from electronic equipment as well as EM interference between devices within it. Numerical full-wave EM simulators, such as a finite-difference time-domain method, have been essential to design NSS. Although numerical EM simulations are rigorous, they require large memory and CPU time. This article validates an analytical transmission-line method for calculating the inter-decoupling ratio of NSS measured with a pair of loop antennas. Furthermore, this article devises a simple method on the basis of a variational method and EM duality concept for calculating the transmission attenuation power ratio of NSS placed on a microstrip line. The devised method is shown to be able to reproduce the measured transmission attenuation power ratios of commercially available NSS within 10% accuracy and with computational time much shorter than numerical full-wave EM simulators.