Basic investigations of 35 GHz reflectarrays and tunable unit-cells for beamsteering applications

Three realisations of 35 GHz reflectarrays with fixed beam are presented. The first single-layered reflectarray uses variable patches as phase-shifting element and serves as reference. The second one, employing patches of variable size loaded with variable length slots in the ground plane, and the third one, a double-layered reflectarray using stacked patches of variable size, are designed to achieve higher bandwidth. In the second part of the paper a novel concept for a tunable reflectarray unit cell using liquid crystals is presented and verified. Measurements performed in a waveguide simulator were able to demonstrate 300deg phase tunability of a unit cell, by applying voltages up to 40 V