A Single-Layer Dual-Wideband Dual-Circularly Polarized Quad-Beam Reflectarray Antenna Based on Hybrid Phase Compensation for Millimeter-Wave/5G Communication Systems

A single-layer dual-wideband (dual-WB) dual-circularly polarized (dual-CP) reflect-array (RA) for 5G applications operating in the Ka-band is designed, fabricated, and experimentally tested in this work. The unit cell of the RA is composed of the adjacent crossed bow tie and split-ring with a short dipole embedded in a reflecting aperture, allowing dual-band operation at 26 GHz and 39 GHz, respectively. Utilizing the hybrid phase compensation approach allows the RA cells to separately manage the reflection phase delay of orthogonal CP beams at both designated bands. This results in four pencil beams that can be generated in four arbitrary directions. The proposed RA is fabricated and tested with a thin substrate thickness of 0.13λ<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">_low</i> (0.2λ<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">_up</i>), where λ<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">_low</i> (λ<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">_up</i>) is the free-space wavelength at 26 GHz (39 GHz), producing asymmetrically scattered dual-WB dual-CP beams in both operating bands. The measured peak gains are 31.5/31.4 dBic for right-hand CP (RHCP)/left-hand CP (LHCP) with aperture efficiencies of 37.4%/36.3% at the lower band and 34.1/34.3 dBic with aperture efficiencies of 30.5%/31.6% at the upper band. Furthermore, for RHCP/LHCP incident waves, the measured 1-dB gain bandwidths are 14.8%/14.2% and 12.3%/13.2% at the lower and upper bands, respectively. The proposed RA is attractive for 5G applications due to its compactness and versatility in achieving polarization diversity and multi-beam radiation patterns at both frequency bands.