Polar, thinned-polar, and linear spiral sampling using the UCLA bi-polar planar near-field measurement system: a comparative study

The determination of an antenna´s far-field pattern from near-field measurements has become an integral part of modern antenna measurements. Planar near-field scanning, whose implementations include plane-rectangular, plane-polar, and the recent bi-polar, has enjoyed particular popularity due to the relative simplicity involved in the data acquisition and processing. The UCLA bi-polar near-field scanner consists of an antenna under test (AUT) mounted to a rotary positioner which rotates about one axis and a probe antenna mounted to a probe arm which rotates about a second axis. The bi-polar near-field measurement scanner´s robotic positioning system and customizable motion control software allow great flexibility in the sample arrangements which may be explored. This paper compares bi-polar planar near field measurements acquired using three different sampling arrangements: polar, thinned-polar, and linear spiral. An interpolation/fast Fourier transform (FFT) based near-field to far-field processing technique is applied to each of these sample arrangements. A comparison and discussion of the resultant measured antenna patterns for a waveguide-fed slot array are included.<>