Nearfield to Farfield Transformation of a Small Patch Antenna by Using Planewave Spectrum Method

Modern planar scanning techniques in the near-field measurement of antennas and scatters are based on the plane-wave spectrum (PWS) representation of the field. The theoretical development of planar near-field antenna measurements is usually based on this plane wave spectrum representation of electromagnetic fields. This work provides a detailed derivation of the coordinate-free form of the near-field to far-field transform that is central to the planar near-field measurement methodology. A patch antenna that works at 10GHz is designed and used as the validation example. Results from 3D electromagnetic simulation and PWS method correlate well demonstrating that PWS can be used to predict the antenna's far-field once the near-field measurement is completed. This PWS method is suitable for quickly characterizing antennas used in nowadays's mobile system without conducting antenna measurement in an anechoic chamber. In this paper, the PWS method is revisited and demonstrated that it can be used to analyze the miniaturized antenna used in mobile systems.