Elemental probes for planar near-field antenna measurements

With planar near-field antenna measurements, a small probe is used to measure the radiating electromagnetic fields in the near-field of the antenna under test (AUT). The measured near-field data is transformed into far-zone antenna patterns using Fourier transforms. Practical probes are not perfectly isotropic, so some form of probe pattern compensation must be used to obtain accurate results. This paper examines several theoretical models that approximately characterize the probe patterns and can be used for probe pattern compensation when the probe size is small in terms of wavelengths. The theoretical models are an elemental electric current, an elemental magnetic current, a Huygens source, and a generalized elemental probe with given E-plane and H-plane beamwidths. The comparison of these different elemental probe models within the same mathematical framework clarifies their similarities and differences.