60 GHz Low-Profile, Wideband Dual-Polarized U-Slot Coupled Patch Antenna With High Isolation

This paper presents a low-profile, highly isolated, wideband, U-shaped slot-coupled dual-polarized patch antenna for the 60 GHz frequency band. The proposed antenna exhibits broadband characteristics that entirely cover the 60 GHz industrial, scientific, and medical (ISM) band, by forming additional resonance at the U-shaped coupled slot. The port isolation is improved by up to 38.6 dB via circulating current in the feed line of the isolation port, which is caused by a reverse placement between the current distributions of the circular patch and U-shaped slot. This phenomenon occurs at the resonant frequency point of the circular patch and is caused by inducing currents of the U-shaped slot and the patch orthogonally to the feeding line. The
$2.2 \times 2.2\times 0.066\lambda _{0}^{3}$
-sized antenna exhibits a 15% impedance bandwidth, 20.4% 3 dB gain bandwidth, and 8.6 dBi peak gain. The port and polarization isolations of the proposed antenna are higher than 37.2 and 18 dB, respectively. When compared with other reported millimeter-wave dual-polarized antennas, the proposed antenna shows the widest 3 dB gain bandwidth and the highest isolation with the lowest profile.