A Low-Profile Three-Port Antenna for Compact Polarization and Pattern Diversity Systems

We propose a compact three-port antenna enabling polarization and pattern diversity at the 915 MHz ISM band. In order to achieve small-form-factor, the proposed design combines a miniaturized bow-tie patch split in half with an air-gap and a short top-loaded folded monopole. The folded monopole is located along the gap in the middle of the patch on a small common ground. The complementary characteristics of voltage-current distribution between the patch and monopole in the middle allows them to be co-located with minimal mutual coupling effects. The patch is fed by aperture coupling and feed probe independently to produce two orthogonally polarized broadside radiation patterns.