Radiation pattern measurements of small isolated antennas

We present a system developed for measuring small antennas; in particular, for measuring their radiation patterns in a spherical format. The antenna under test (AUT) is positioned with an elevation over the azimuth positioner made entirely from dielectric materials. The test signal can be fed from a built-in generator powered by a battery. Owing to the elimination of the feeding cable normally used in an antenna measuring setup, measurements are run in conditions that reconstruct the actual operational environment with accurate results. The measuring time is short, as the rotational speed of the dielectric positioner is sufficiently fast. With the use of a microwave backward projection technique, it is possible to estimate the field distribution inside a lossy object placed next to the AUT, thus providing a quick, nondosimetric evaluation of the SAR distribution inside a phantom head.