Planar Dual-polarized Slot Antenna for UWB MIMO Applications

In this paper, we have proposed a compact, planar dual-polarized slot antenna for ultra-wideband (UWB) applications. Two orthogonal polarizations are realized by employing different feeding techniques which lead to achieving high isolation. The horizontal polarization is excited by an elliptically tapered slot while the vertical polarization is obtained by a monopole with a half-circle slot. The two slots are emerged and embedded in the ground plane which is printed on one side of the substrate. The tapered slot is fed by a microstrip-line-to-slotline transition which consists of a folded slot and a stepped microstrip line. The feeding transition acts as a balun and is printed on the other side of the substrate. On the same side, a microstrip line terminated with a circular patch is adopted to feed the half-circle slot. Compared with other designs in the literature, the planar antenna structure has a compact size of 30 mm x 30 mm x 0.8 mm and the reflection coefficients of both ports are below -10 dB over a wide frequency band from 3-10 GHz. The isolation over the entire frequency band is above 18 dB. All these characteristics make the proposed antenna a promising candidate for UWB dual-polarized multiple-input-multiple-output applications.