Sub-THz U-Slot Coupled Stacked-Patch Radiating Elements for Dual-Polarized MIMO Array Antennas

Several sub-THz (D-band, 136 - 148 GHz) dual-polarized array elements (unit cells, UCs) implemented in a multi-layer PCB technology are investigated in the infinite array environment. The elements are stacked-patch antennas with unbalanced aperture-coupled feeds (U-slots), having a slant 45 deg. polarization. We demonstrate that a baseline half-wavelength cavity-backed UC is capable of achieving ≤ 3.7 dB scan loss in the 60 deg. conical scan range and (132–149) GHz bandwidth. For the increased UC size, however, active polarization channel isolation drastically degrades and the element experiences scan blindness. To address this problem, a UC modification is introduced that suggests using a single-row mushroom-type electromagnetic band-gap structure along the UC sidewalls. Simulated results evidence the realized UC decoupling and elimination of the scan-blindness anomalies in the full visible scan range, with scan loss ≤ 4.2 dB in the 55 deg. conical scan range and (136–148) GHz bandwidth.