A 3-D Single-stage Differential Mode Filter Modeling with Mutual Couplings and Layout Optimizations

EMI filters are traditionally designed to attenuate the low-frequency harmonics as the filter exhibits an insertion gain of -20 dB/decade per added filter component which inherently attenuates the high-frequency noise. However, the self-parasitics of EMI filter components and mutual couplings between the components and traces decrease the attenuation capability of the filter at higher frequencies. This paper model the filter components and traces in ANSYS high-frequency structure simulator (HFSS) tool and attempts to relate the couplings to the filter and trace placements. A single-stage differential mode (DM) filter has been analyzed and optimum component placement has been identified. It has been shown that on average 17 dB higher insertion gain can be achieved with layout optimization in comparison to commonly used component placement.