Broadband Dual-CP Multi-Stage Sequential Rotation Arrays with Independent Control of Polarizations Based on Dual-CP Magneto-Electric Dipole Elements

In this paper, broadband dual-circularly-polarized (dual-CP) antenna arrays with independent control of polarizations are proposed and demonstrated at K -band. By introducing folded Γ-shaped end loadings and corner truncation, a dual-CP magneto-electric dipole (ME-dipole) element with a compact footprint and a broad bandwidth of 22.5% is realized. Based on such element, a 2 × 2-element sequential rotation 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 4 × 4-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 sequential rotation 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 a LHCP pencil beam and a RHCP vortex beam pointing at distinct directions, confirming the capability of independent control of polarizations.