- Conference Article
- 10.4271/2026-26-0368
Black Box Approximation of EMI/EMC Filter Parasitic’s
- Jan 16, 2026
- SAE technical papers on CD-ROM/SAE technical paper series
- Devbrat Pandey + 3 more +3
<div class="section abstract"><div class="htmlview paragraph">Selecting the right EMI/EMC filter is a major challenge when system noise levels exceed compliance or pre-compliance limits. Inline PCB filters are designed to mitigate noise in standalone conditions, but their behavior changes when integrated into a larger system due to unknown parasitic’s. These parasitic’s can disrupt electromagnetic compatibility (EMC), leading to non-compliance [<span class="xref">1</span>, <span class="xref">2</span>]. To address this, engineers often use off-the-shelf EMI filters, but determining their real-world effectiveness remains complex. Even with simulation-based methods, accurately predicting insertion loss and attenuation is difficult due to limitations in conventional modeling approaches [<span class="xref">4</span>, <span class="xref">5</span>].</div><div class="htmlview paragraph">Traditional SPICE-based simulations rely on static models defined at specific frequency points, with interpolated values for intermediate frequencies. This interpolation introduces inaccuracies, affecting the precision of simulated results [<span class="xref">6</span>, <span class="xref">8</span>]. To overcome these limitations, we propose a methodology that reconstructs a realistic EMI/EMC filter model based on insertion loss characteristics under symmetrical and unsymmetrical conditions.</div><div class="htmlview paragraph">Our approach involves deconstructing the EMI/EMC filter into its subcomponents—X-capacitance, Y-capacitance, common mode choke CMC, busbar, and PCB traces—and parameterizing them using CST simulations [<span class="xref">6</span>, <span class="xref">8</span>]. Instead of relying on physical measurements, which are prone to parasitic influences, we extract subcomponent values from datasheets. We focus on dominant parasitic elements exceeding 1 pF and 1 nH, as lower values predominantly affect GHz-range frequencies rather than the MHz-range compliance limits [<span class="xref">4</span>, <span class="xref">5</span>], analyzing impact of parasitic’s on insertion loss, resonance, and damping characteristics, a filter model that represents real-world behavior with a certain error percentage [<span class="xref">2</span>, <span class="xref">4</span>, <span class="xref">5</span>].</div><div class="htmlview paragraph">This methodology results in a high-fidelity EMI/EMC filter model with minimal deviation from actual performance. It enables precise pre-compliance conducted emissions simulations and facilitates optimized filter selection and tuning based on system-specific noise conditions.</div></div>
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