Ka-Band Huygens Antenna Array With Very High Aperture Efficiency and Low Sidelobes

Abstract

A Ka-band Huygens antenna array with extremely high aperture efficiency (AE) and low sidelobe levels is reported for 5G millimeter-wave (mm-wave) wireless applications. The basic array element is an innovative Huygens subarray consisting of two open rectangular waveguides that form an aperture consisting of a 1 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> 2 set of orthogonal, tightly coupled electric and magnetic elements separated by a virtual gap that are balanced, in- phase, and radiate Huygens cardioid patterns. A larger 8 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times16$ </tex-math></inline-formula> element array is then realized with 64 of these 1 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> 2 subarrays. With excitations of equal amplitude, the full broadside-radiating array achieves an AE up to 97.5% in the operating bandwidth, which is very close to the 100% limit associated with an ideal uniform aperture distribution. Moreover, a highly efficient and compact feed network with tapered-amplitude and in- phase excitations from the array center to its edges is designed to achieve sidelobe and backlobe levels less than −20 dB. The −10 dB impedance bandwidth covers 26.7–29.65 GHz, and the peak realized AE (RAE) reaches 82%. A full-aluminum array prototype was fabricated with standard machining processes and tested. The measured performance characteristics agree well with their simulated values, confirming the efficacy of their designs.