A Circularly Polarized Sub-Terahertz Antenna With Low-Profile and High-Gain for 6G Wireless Communication Systems

A low-profile high-gain fully-metallic circularly polarized (CP) Fabry–Perot cavity (FPC) antenna using laser cutting technology at 300 GHz is presented. The CP-FPC antenna consists of seven metallic layers arranged from the bottom to the top: a ground layer, an integrated stepped horn element (three layers), a coupling slots layer, a cavity layer, and an aperture-frequency selective surface (FSS) layer. The high gain and self-generation of circular polarization are made by using this FSS layer by introducing periodic hexagonal–shaped aperture in a thin metallic layer. The aperture–FSS layer is used to excite two orthogonal modes of equal in magnitude and in phase quadrature, thus obtaining the RHCP radiation. The proposed CP-FPC antenna structure achieves a measured peak RHCP gain of 16.5 dBic at 292 GHz. The antenna achieves a measured impedance bandwidth of 281– 305 GHz for the reflection coefficient less than −10 dB. The axial ratio (AR) bandwidth AR ≤3 dB is 5.12 GHz from 292.8 to 297.92 GHz. The fabricated CP-FPC antenna uses a low-cost laser cutting technique with a low-profile and an area of 2.6 mm $\times2.6$ mm $\times1.24$ mm. The experimental results confirm a good agreement between the simulation and the measurements.