Wideband and Low-Profile Integrated Dual-Circularly-Polarized Transmit-Arrays Enabled by Antenna-Filter-Antenna Phase Shifting Cells

In this article, the theory, design, and demonstration of wideband and low-profile dual-circularly polarized (dual-CP) transmit arrays (TAs) are reported, which support independent beamforming for left-/right-handed CP waves. This is achieved by utilizing an antenna–filter–antenna configuration for the TA unit cells with a profile of only about
$0.11\lambda _{0}$
, which consists of receiving and transmitting stacked patches connected by two microstrip delay lines. By utilizing the phase delay lines and unit cell rotation, the dynamic phase and the Berry phase can be simultaneously exploited for providing continuous dual-CP transmissive phase compensation insensitive to the angle of incidence. The diffraction analysis of a linear gradient array of the proposed cells confirms its wideband performance of abnormal refraction. In addition, broadband CP planar feed arrays were designed and verified for functioning as low-profile feeds with symmetrical patterns for the TAs. As proof-of-concept examples, two
$K$
-band dual-CP TAs integrated with the planar feeds were synthesized, fabricated, and measured, possessing a total profile of about
$7.1\lambda _{0}$
. The two prototypes offer either symmetrical or asymmetrical dual-CP beams over a wide bandwidth. Their measured peak gain is higher than 22 dBic, while the joint
$S_{11} < -15$
dB, axial ratio < 2 dB, beam squinting <3°, and 2–dB gain bandwidth is wider than 12%. The design methodology and the proposed dual-CP TAs are useful in communication systems for space and wireless applications.