Estimation of radiation efficiency of GaN Half-bridge based submodule system for radiated EMI prediction

Predicting radiated emissions in large and complex power systems is difficult under a single set operational conditions, however when flexibility is introduced it becomes near impossible without using thousands of Monte-Carlo type simulations. In this paper it is suggested to estimate the radiation efficiency (i.e. transfer function) of a power system based on a novel theoretical model and a limited amount of measurements under operating conditions. The switching power system is modeled as a LTI-system that is excited by a known Sinusoidal Pulse Width Modulation (sPWM) source, i.e. the switching node voltage waveform. The theoretical model simplifies the estimation of the sPWM power spectrum, while its amplitude is also independent of modulation index. By measuring radiated electric fields and calculating Effective Radiated Power (ERP) one can estimate the system radiation efficiency in a novel way. The derived efficiency can eventually be used to optimize the radiated EMI, for instance by avoiding highly radiative frequencies in the signal generation.