C-/Ka-Band Aperture-Shared Dual Circularly Polarized Heterogeneous Reflectarray for Vehicular Communications

Abstract

This article presents a C-/Ka-band aperture-shared reflectarray (RA) antenna with dual circular polarized (CP) high gain beams for vehicle communications. A dual-polarized patch antenna fed by a branch line coupler is designed as the C-band unit cell (UC). The phase-shifting for the C-band right-hand circular polarization (RHCP) and left-hand circular polarization (LHCP) can be independently controlled by adjusting the phase delay lines connected to the coupler. In contrast, the Ka-band dual circular polarization independent beam-shaping is based on the strategy of combining the Pancharatnam-Berry (PB) phase and dynamic phase. Two different kinds of Ka-band UC are designed and planted into the metallic and non-metallic regions of the C-band patch antenna, forming a heterogeneous Ka-band RA that is seamlessly integrated into the C-band RA. By properly selecting the size and rotating angles of the Ka-band UCs, the RA can also independently manipulate the LHCP and RHCP wavefronts in Ka-band. In addition, the phase-shifting for C-band and Ka-band do not affect each other. Note that the proposed strategy differs from state-of-the-art works, which either interleave UCs or place different UCs in separate layers. A RA operating at 4.4 GHz (C-band) and 30 GHz (Ka-band) with dual CP decoupled beams are fabricated and experimentally verified for demonstration.