Dual polarized UWB antenna for free-space characterization of dielectric objects

This paper presents a dual polarized antenna for UWB sensor applications. The antenna consists of four circular radiating elements forming two dipoles excited in even mode in both polarizations. The geometry avoids directly crossed baluns but requires two power dividers and four tapered baluns because of four feeding points. It provides an input return loss better than 7dB over a frequency band from 2GHz to 5.7GHz. The isolation between both ports is better than 30dB. At 5GHz a gain of 5.2dB is achieved. The dimensions of the antenna including the feeding network and absorbers are 50mm×50mm×143.5mm. A line array of four antennas was built as part of a free-space measurement system for the non-contacting permittivity determination of irregular shaped dielectric objects.