A Dual-Polarized Cavity-Backed Annular Slot Antenna of High Isolation

In this paper, we propose a uni-directional, dual-polarized MIMO antenna for indoor 2.4-GHz WLAN systems. This antenna consists of a cavity-backed annular slot and two inverted microstrip feed lines which are mutually orthogonal. To further suppress the cross-polarized levels and enhance the ports isolation two grounded strips are symmetrically mounted in the opposite direction of the feed lines and have the same size with them. By using this way the electrical field distributions in slot are more symmetrical. The experimental results show that the prototype antenna has more than 26-dB ports isolation and the cross-polarized levels are 27dB less than the co-polarization over the working band. This designed antenna has compact size and can be easily applied in indoor MIMO WLAN base stations.