Near-field characterization of PCBs for radiated emissions prediction

A method for characterizing printed circuit boards as sources of radiated emissions is proposed. The method uses probe measurements made in the very close vicinity of the device under test (DUT). These measurements can be processed to determine the emission level at any distance from the DUT. Due to its near-field nature, this technique does not require anechoic electromagnetic-compatibility (EMC) rooms or open area test sites, which makes it very attractive from an economical point of view. The key point of the characterization is the expansion of the current distribution on the circuit board into a set of filamentary current basis functions. The interaction between the basis functions and the near-field probe is calculated with the method of moments. Accurate field predictions were obtained for planar structures having a 1.25-mm wire spacing