Influence of conductive layer geometry on maximal impedance frequency shift of zig-zag ferrite EMI suppressor

Abstract

This paper explores an influence of conductive layer geometry on electrical parameters of ferrite electromagnetic interference (EMI) suppressor, which consists of conductive layer in ferrite monolithic structure. Near ferrimagnetic resonant frequency, component has maximal impedance and efficiently suppresses noise. In order to achieve better suppression (i.e., larger impedance), conductive layers should be longer. Nevertheless, longer conductive lines introduce parasitic capacitance, which causes the maximal impedance frequency shift. Because of that, the frequency range where component can be used for efficient EMI suppression is shifted towards lower frequencies, and designing process should be very careful. In this paper, we present simulation of frequency dependent impedance for different geometry parameters of conductive layer. Results for the inductance and the maximal impedance frequency shift of the proposed EMI suppressors are presented in the range 1 MHz3 GHz. Proposed EMI suppressors were experimentally tested using Agilent 4287A RF LCR meter. Comparison of simulated and measured values of impedance shows a good agreement. © 2006 IEEE.