Far-Field Prediction by Only Magnetic Near Fields on a Simplified Huygens's Surface

For radiation source locating above a ground plane, its far field can be predicted by only the magnetic near field through the method proposed in this paper. This method applies the finite element method to get the equivalent current sources from the tangential magnetic near fields. With the equivalent current sources, the far-field radiation can be calculated based on Huygens's principle and image theory. The magnetic near field is scanned on a Huygens's surface that encloses the source with its ground. In this paper, this Huygens's surface was first proposed as a five-surface cube on the ground. Then, the Huygens's surface was further simplified by using four lines instead of four side walls to make the proposed method easier in regards to practical near-field scanning. Several numerical examples were tested to validate the proposed method. In addition, the proposed method was validated experimentally by using a patch antenna. The performance of using only the top plane near fields was also investigated and discussed. By using only the magnetic near fields on the simplified Huygens's surface, the proposed method significantly saves measurement time and cost while also retaining good far-field prediction.