Circularly-Polarized Reconfigurable Transmitarray in Ka-Band With Beam Scanning and Polarization Switching Capabilities

TLDR

The authors design and experimentally characterize a 400‑element Ka‑band electronically reconfigurable transmitarray with beam‑steering and circular‑polarization switching, and develop a planar substrate‑integrated waveguide focal source array that halves the focal distance to improve compactness while preserving performance. The array employs linearly polarized unit cells with 180° phase‑shifting, uses numerically compared rotation schemes to synthesize a broad‑band circularly polarized beam, and adopts a random cell distribution to suppress cross‑polarized side‑lobes during beam scanning, while the focal source array is a planar substrate‑integrated waveguide design. Experimentally, the prototype achieves ±60° 2‑D beam steering, a 20.8 dBi broadside gain at 29.0 GHz, 14.6% 3‑dB bandwidth, 58% radiation efficiency, and an axial ratio below 2 dB, with comparable performance demonstrated for the compact planar substrate‑integrated waveguide focal source array.

Abstract

The design, realization, and experimental characterization of a 400-element electronically reconfigurable transmitarray operating in the Ka-band is presented. It is based on linearly polarized unit-cells with 180° phase-shifting capability. Several sequential rotation schemes have been compared numerically to generate a circularly polarized beam over a broad frequency band, and a random distribution has been selected to mitigate spurious cross-polarized side-lobes when scanning the main beam. The 2-D electronic beam-steering capabilities of ±60° have been verified experimentally. The prototype, illuminated by a horn antenna as a focal source, exhibits a broadside gain of 20.8 dBi at 29.0 GHz and a 3-dB bandwidth of 14.6% with radiation efficiency of 58%. The axial ratio remains below 2 dB within this bandwidth. Next, a planar substrate integrated waveguide focal source array was designed in order to reduce the focal distance by about 50% and thereby significantly improve the antenna compactness, and similar radiation performance is demonstrated numerically and experimentally.