A Dual-Polarized Square-Ring Slot Antenna for UWB, Imaging, and Radar Applications

In this letter, a dual-polarized slot antenna for ultrawideband (UWB) applications is proposed. The slot has an overall shape of a square ring whose four arms are identical and stepped rectangular. While two adjacent arms of the ring are microstrip-fed and are responsible for the orthogonally polarized fields, the other two arms are introduced to make the structure symmetric and reduce the cross polarization. The impedance matching and isolation are controlled by properly shaping the slot arms and the feed section and by insertion of narrow metallic and slot stubs. The measured impedance bandwidth is 120% (3.0-12.0 GHz). The isolation is better than 20 dB over most of the band. With the help of radiation patterns and aperture electric field distribution, the dual-polarized nature of the antenna is justified. The antenna will be useful for UWB multiple-input-multiple-output (MIMO) transmission, polarimetric radar, and medical imaging applications.