Low-Profile Six-Port Circular Patch Antenna With Six Triple-Shorted Dual-Resonant 60°-Disk Sectors to Generate Six Uncorrelated Waves for Wideband Mobile MIMO Antennas

Abstract

A low-profile six-port circular patch antenna generating six uncorrelated waves in a wide band of about 5.8-7.5 GHz (based on 3:1 VSWR, fractional bandwidth about 25%) is presented. The antenna thickness is 1.4 mm (about 0.027λ at 5.8 GHz), which includes a 0.4 mm thick FR4 substrate with the circular patch printed thereon and an additional 1.0 mm thick air layer to achieve a low-permittivity antenna substrate. The circular patch with a diameter of 40 mm (about 0.77λ at 5.8 GHz) is separated into six 60°-disk sectors by using three linear slots across the patch center and sequentially rotated by 60°. Each disk sector is short-circuited to the ground plane through three properly located shorting pins. It thus makes the 0.5-wavelngth and 0.25-wavelength resonant modes excited at nearby frequencies to form a dual-resonant wide band for each port. Additionally, the six ports in the proposed antenna have their port isolation larger than 10 dB and the corresponding six radiating waves have very low envelope correlation coefficients (less than about 0.02) over the wide band. That is, six uncorrelated waves suitable for MIMO (multi-input-multi-output) operation are obtained. The proposed antenna can find applications for wideband mobile MIMO antennas to cover 6.425-7.125 GHz of the possible new mobile communication band or 5.925-7.125 GHz for the new unlicensed WiFi-6E band.