Near-field test ranges are typically indoor configurations that occupy a relatively small space. This type of range uses a small RF probe antenna that is scanned over a surface surrounding the test antenna. Range lengths can be very short even to the point to where the probe nearly touches the antenna structure. During the measurement, near-field phase and amplitude information is collected over a discrete matrix of points. This data is then transformed to the far-field using Fourier techniques. The resulting far-field data can then be displayed like other conventional far-field antenna measurements.
In addition to obtaining far-field data, back-transforming to the antenna's aperture produces aperture field distribution information. This offers the ability to perform element diagnostics on multi-element phased array antennas.
|Spherical Near-Field||Cylindrical Near-Field||Planar Near-Field|
In near-field testing the test antenna is usually aligned to the scanner's coordinate system and then either the probe or the test antenna is moved. In practice it is easier and more cost effective to scan the RF probe over linear axes or the test antenna over angular axes.