Predicting EMI emission levels using EMSCAN

The EMSCAN is a device that measures the RF currents on a functioning PC (printed circuit) board. The EMSCAN measures the near-field magnetic fields from the board. This can be calibrated to the RF current at the frequency of interest. Using the Hertzian dipole approach and a scaling factor, it is shown that the data from the EMSCAN can be used to predict the electric field strength from that PC board. Differences between the measured and prediced data vary from less than 1 dB to about 7 dB. This is quite reasonable agreement for this application as long as care is used if the levels are close to the regulatory limits