Towards nonlinearity measurement and simulation using common EMC equipment

Integrated circuit (IC) models that predict functional failure are necessary for predicting the immunity of systems to electromagnetic interference (EMI). The integrated circuit immunity model for conducted immunity (ICIM-CI) of IEC 62433-4 assumes that the IC terminals still behave linearly at injection power levels that cause susceptibility. This hypothesis should be systematically verified when modelling integrated circuits for EMC, but this is not always straightforward. A simple measurement set-up using a directional coupler and a spectrum analyser is demonstrated to verify this linearity hypothesis using commonly available equipment. The measured reflected spectrum can be transformed into the |X₁₁| parameter, which is the non-linear extension of the S₁₁ parameter.¹ X-parameters may be the key to predict susceptibility by simulation when the linearity hypothesis is invalid.