Dielectric versus patch-based implementations of Risley Prism transmit-arrays in Ka-band

Abstract

Many millimeter wave applications related with 5G and Satellite on the move (SoTM) communications rely on cost-effective high-gain antennas with wide beam scanning. Mechanical steering solutions can reduce the complexity and cost of the fully-electronic beam steering counterpart (e.g. phased arrays). Mechanical scanning with Transmit-array (TA) antennas can provide a balanced compromise between cost, size, and efficiency. TAs are usually associated with a thin metasurface composed by a tailored distribution of patch-based unit cells. However, fully-dielectric unit cells can also be used for the design of the aperture, which can be viewed as gradient index (GRIN) lenses. In this work we compare fully-dielectric and stacked patch-based implementations of the Risley Prism scanning concept. This configuration consists of two independent axially rotating TA that can provide elevation and azimuth mechanical scanning. The dielectric version can further reduce the cost of these antennas trading-off with some antenna efficiency degradation caused by material losses, free-space mismatch, and higher lens thicknesses. This work also includes the experimental validation of the dielectric Risley prism implementation, less explored in the state of-the-art.