Broadband Dual-CP Multistage Sequential Rotation Arrays With Independent Control of Polarizations Based on Dual-CP Magnetoelectric Dipole Elements
Weimin Zeng, Xin Yu Wu, Fan Wu, Yan Zhang, Zhi Hao Jiang, Wei Hong, Kwai-Man Luk
Abstract
In this article, broadband dual-circularly polarized (dual-CP) antenna arrays with independent control of polarizations are proposed and demonstrated at the K-band. By introducing folded <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Gamma $ </tex-math></inline-formula> -shaped end loadings and corner truncation, a dual-CP magnetoelectric dipole (ME-dipole) element with a compact footprint and a broad bandwidth of 22.5% is realized. Based on such element, a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\times2$ </tex-math></inline-formula> -element sequential rotation (SR) subarray is constructed. By employing a high dielectric constant substrate, a stacked array feeding configuration is devised by placing two sets of microstrip feeding circuits above and below the ground plane for independent dual-CP beamforming. Importantly, the feeding circuitry is fully confined within the area of the array elements without occupying any extra space. Furthermore, a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4\times4$ </tex-math></inline-formula> -element array is synthesized for obtaining dual-CP radiated beams over a broad bandwidth with improved CP purity and port isolation via exploiting the double-stage SR feeding strategy. The fabricated array prototype experimentally achieves a 3-dB axial ratio bandwidth of wider than 28.5%, a 3-dB gain bandwidth of about 23.2%, as well as a −10 dB impedance bandwidth of greater than 50% within which the port isolation is higher than 15 dB. Moreover, the dual-CP beamforming is also showcased by a second array example that generates an LHCP pencil beam and an RHCP vortex beam pointing at distinct directions, confirming the capability of independent control of polarization.