Near-field scanner

Electromagnetic near-field scanner (NFS[1]) is a measurement system to determine a spatial distribution of an electrical quantity provided by a single or multiple field probes acquired in the near-field region of a device under test possibly accompanied by the associated numerical post-processing methods enabling a conversion of the measured quantity into electromagnetic field.

The voltage pattern is usually mapped on planar, cylindrical or spherical geometrical surfaces as a collection of a finite number of spatial samples.

Determination of a far-field radiation pattern constitutes the primary application of antenna near-field scanners.

This novel technique offered an attractive alternative to conventional open area test sites for measurements of high gain, electrically large antennas or antenna arrays (gain > 20 dBi, diameter > 5λ) in an indoor, controlled and all-weather capability environment.

Among well recognized and analyzed errors of the near-field measurements, multiple reflections between an antenna under test (AUT) and an electromagnetically non-transparent field detection system (scatterer) belong to the most contributing errors when the AUT has a high gain.

In order to quickly localize field emission in the frequency domain, time domain detection techniques together with signal processing based on fast Fourier transform could be employed, e.g. utilizing a digital storage oscilloscope as a signal receiver.