Ultrathin Single-Layer Dual-Band Dual-Circularly Polarized Reflectarray for K-/Ka-Band Satellite Communications

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
$0.0508\lambda _{K}$
(
$\lambda _{K}$
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
$2\times 2$
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,
$2\times 2$
bit dual CP phase coding at K-band and
$3\times 3$
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.