Ultra-Wideband Dual-Polarized Patch Antenna With Four Capacitively Coupled Feeds

A novel dual-polarized patch antenna for ultra-wideband(UWB) applications is presented. The antenna consists of asquare patch and four capacitively coupled feeds to enhance theimpedance bandwidth. Each feed is formed by a vertical isoscelestrapezoidal patch and a horizontal isosceles triangular patch. Thefour feeds are connected to the microstrip lines that are printedon the bottom layer of the grounded FR4 substrate. Two taperedbaluns are utilized to excite the antenna to achieve high isolationbetween the ports and reduce the cross-polarization levels. In orderto increase the antenna gain and reduce the backward radiation,a compact surface mounted cavity is integrated with the antenna.The antenna prototype has achieved an impedance bandwidth of112% at (|S11 | ≤ -10 dB) whereas the coupling between thetwo ports is below -28 dB across the operating frequency range.The measured antenna gain varies from 3.91 to 10.2 dBi for port 1and from 3.38 to 9.21 dBi for port 2, with a 3-dB gain bandwidthof 107%