Far-field radiation estimation from near-field measurements and image theory

This paper proposed a near-field to far-field transformation method for the radiation sources located on a large ground plane, based on the Huygens´s principle and image theory. This method uses the tangential electromagnetic fields on a small near-field plane and the vertical electric fields, one tangential component (parallel to the ground plane) of magnetic fields around the near-field plane to extract the equivalent current sources. The far-field radiations are calculated from these equivalent sources and their images. The application of this method in several simulation models indicates that it has very good performance on both simple printed circuit boards and antenna radiation estimation. The method proposed in this paper can decrease the total scanning area in real measurements.