EMC Simulation Best for Determining Relative – Not Absolute – Emissions

For those not based in the Bay Area, we will occasionally cover IEEE EMC Society Santa Clara Valley Chapter events that we think are relevant to Compliance Today readers.  After all, the IEEE Santa Clara Valley Section is located in the heart of Silicon Valley, and is the world’s largest IEEE section.

Tuesday featured an interesting presentation by Apple’s EMC Technologist Federico Centola on EMC Simulation.  MET Labs’ James Bojorquez was in attendance and took these notes:

EMC simulations are generally not used for predicting emissions, but are useful for quantifying the relative difference between design options.

It is important to understand top simulation result uncertainties, such as:

  • Amount and type of geometry simplifications
  • Numerical techniques used
  • Implicit and explicit assumptions used

If the simulated result variation between different designs is less than the result uncertainties, then the simulations are meaningless.

Centola also noted:

  • The higher the frequency, the lower the accuracy
  • CAD Files are not intended for EMC simulation – they need to be simplified
  • Some models are too complex to be simulated

He gave an example of an issue with a Wi-Fi antenna and air vents in a laptop Apple was designing, and how they used the simulation to optimize it. They essentially stripped everything out of the laptop and made assumptions as to what the issue was and focused on that as a fix.

They assumed seams and gasketing were not the problem, nor anything else.  Again, the simulation needs to be simple, and smart assumptions need to be made in order for the tool to be effective.

To learn more about EMI avoidance, consider registering for an EMC Design & Testing Seminar, co-hosted by MET and Wurth Electronics on March 31 in Santa Clara.

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