The impact of near-field scanning size on the accuracy of far-field estimation

The impact of near-field scanning sizes on the accuracy of far-field estimations is studied using a U-shape trace above a large ground plane as an example. Simulation model is built in commercial software and the planar near fields above the trace are obtained. Fourier Transform of the planar near fields is used to calculate the far-field radiations. Different sizes of planar scanning area are chosen and their corresponding computed far field patterns and maximum values are compared with those obtained by the software. It demonstrates that too small scanning size may lead to large errors in far-field calculations. Relationship between scanning plane height and planar scanning size is derived for accurate far field estimation, which is guidance for the extraction of accurate IC radiated emission model by planar near-field scanning technique.