An Alternative Approach to Specifying an EMI Filter

There has to be a better way of specifying EMI filter performance – one that shows a filter’s effectiveness in real-life situations. It turns out there is a better alternative test method that fulfills this need. This method is the insertion loss test method for non-50Ω systems, located in Annex C of the second edition of EN 55017 (a.k.a. CISPR 17).
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Be Careful with Input-Output Feedback in Filters

When designing EMI filters how and where the filter is installed is critical to obtain the desired insertion losses. Usually, the effect of a wrong location or installation is not considered in the design of the filter and surprises appear.

Noise Mitigation Analysis of a π-filter for an Automotive Control Module

Electromagnetic interference (EMI) filters are often used on automotive 13.8 VDC power networks to reduce high-frequency noise from being conducted off the printed circuit boards (PCB) and resulting into EMI problems. The filter performance is difficult to predict and often compromised at high frequencies due to parasitics associated with the filter itself, or the PCB layout. The power line filters with Surface Mount Technology ferrite and Multi Layer Ceramic Capacitors are attractive solutions for mitigation of RF noise in high-density automotive PCBs. A lumped-element SPICE model is introduced for optimized π-filter design, including frequency-dependent ferrite component model. The PCB implementation of EMI filter is outlined for optimum filter performance.