Ultrathin Single-Layer Dual-Band Dual-Circularly Polarized Reflectarray for <i>K</i>-/<i>Ka</i>-Band Satellite Communications
Peng Xu, Ruijie Li, Haixia Liu, Kunyi Zhang, Hao Xue, Long Li
Abstract
In this article, we propose an ultrathin dual-band dual-circularly polarized (dual-CP) shared-aperture reflectarray (RA) operating at K- and Ka-band utilizing only a single-layer substrate. First, the ultrathin single-layer RA cell with a thickness of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.0508\lambda _{K}$ </tex-math></inline-formula> (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{K}$ </tex-math></inline-formula> is the free-space wavelength at 20 GHz) is designed. By considering the mutual influence between the RA cells operating at different frequencies, meanwhile by combining the spin-decoupled strategy, thereby a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\times 2$ </tex-math></inline-formula> bit dual CP phase coding strategy for both K and Ka unit cells is realized. Next, the RA illuminated by the CP feed source is designed. To improve the aperture efficiency (AE) of the RA at the Ka-band, the modified phase coding strategy, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\times 2$ </tex-math></inline-formula> bit dual CP phase coding at K-band and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3\times 3$ </tex-math></inline-formula> bit dual CP phase coding at Ka-band, is adopted and the corresponding AEs for left-handed CP (LHCP) and right-handed CP (RHCP) beams are increased to 25.6% and 24.4% at 30 GHz, respectively, as well as the AEs for LHCP and RHCP beams at 20 GHz remaining at 33.6% and 33%, respectively. Finally, the modified RA with a diameter of 220 mm is designed, manufactured, and measured. The measured results are in good agreement with the simulations, generating LHCP and RHCP beams independently at K- and Ka-bands, respectively.