A Low-Profile Pattern and Polarization Diversity Dual-Band MIMO Antenna with Full Azimuth Coverage for Indoor Access Points

A low-profile multi-port dual-band antenna with pattern and polarization diversity is presented for 2.45 and 5.8 GHz bands. The antenna consists of a monopolar patch for vertically polarized (VP) omnidirectional radiation and four combining printed-dipole and tapered-slot elements arranged in a circular shape for horizontally polarized (HP) multibeam radiation, and consequently, both pattern and polarization diversities are achieved in the full azimuth plane. The monopolar patch employs four vias and a square-ring slot to excite \(TM_{01}\) $T{M}_{01}$ and \(TM_{02}\) $T{M}_{02}$ modes at 2.45 and 5.8 GHz, respectively. Each HP element utilizes printed-dipole and tapered-slot modes for the lower and upper bands, respectively. The VP and HP elements are collocated with a common ground plane, which not only allows a low profile but also broadens the lower band of the monopolar mode. The final design with 0.03 \(\lambda _{2.45-GHz}\) ${\lambda }_{2.45-GHz}$ height yields a measured 10-dB return loss bandwidth of 8.6% and 6.7% at 2.45 and 5.8 GHz, respectively, and an isolation \(\ge\) $\ge$ 20 dB among all the ports. Its pattern and polarization diversities are validated by far-field measurements.