Compact, Low Profile, Common Aperture Polarization, and Pattern Diversity Antennas

This paper presents compact and low profile two-port antennas that can provide polarization or pattern diversity schemes from a common aperture. The proposed antennas make use of a novel small microstrip antenna topology with an open area at its waist. The two sections of the small-size microstrip antenna are connected through a magnetic coupling mechanism facilitated by two vertical metallic strips connecting the top plates to the ground plane. This allows for placement of another small antenna element within the same aperture having either polarization or pattern that is orthogonal to the microstrip antenna with low envelope correlation. Topologies of polarization and pattern-diversity antennas are optimized for size reduction and minimum envelope correlation. Although the proposed diversity antenna consists of two antenna elements with different polarizations or radiation patterns, they just occupy about 30% of the area of a conventional microstrip antenna over the same substrate. It is shown that the envelope correlation between radiation patterns of the two antenna elements is lower than -30 dB over the 10-dB return loss bandwidth of the proposed antenna.