Dual-Wideband Dual-Circularly-Polarized Shared-Aperture Reflectarrays With a Single Functional Substrate for K-/Ka-Band Applications

We report, here, the design and experiments of dual-wideband dual-circularly polarized (dual-CP) shared-aperture reflectarrays (RAs) operating at the K-/Ka-band utilizing a single functional substrate. By coupling the adjacent but separated resonances of the H-shaped aperture and circular patch, and utilizing the shorted microstrip phase delay lines, the proposed RA cells can offer wideband performance. Then, these RA cells are interleaved in a shared aperture for the dual-band operation. By combining the dynamic phase and Berry phase compensation techniques, the RA cells can independently control the reflective phase delay of orthogonal CP beams at both of the targeted bands, providing four degrees of freedom for beamforming. The diffractive property of an infinite periodic gradient array of the interleaved K- and Ka- band cells is investigated, which verifies the wideband performance of the proposed cells. Two RAs with a thin panel thickness of
$0.27\lambda _{K}$
(
$\lambda _{K}$
is the free-space wavelength at the K-band) are fabricated and characterized, generating symmetrically and asymmetrically distributed dual-wideband dual-CP beams at the K-/Ka-band, respectively. The measured bandwidths for the two RAs are wider than 14.1% for the K-band right-handed CP (RHCP)/left-handed CP (LHCP) beams and about 11% for the Ka- band RHCP/LHCP beams with both the gain variation and axial ratio of smaller than 2 dB.