Monolithically Integrated Liquid Crystal Tunable Reflective Load for Millimeter-Wave Phase Shifter Applications

The paper introduces a monolithically integrated reflective load employing liquid crystal material as a reconfigurable element for phase shifter applications. The LC material is confined within a micromachined space, and its dielectric properties are controlled through an applied bias voltage. This tunable reflective load finds applicability in reflective-type phase shifters. Operating at a frequency of 28 GHz, the reflective load exhibits a phase variation of 113° as the bias voltage ranges from OV to 25V. The device demonstrates a reflective insertion loss of 3.9 dB, indicating a Figure of Merit (FOM) of 29°/dB. Fabrication of this device is conducted in-house using a multi-layer microfabrication process. To the best of our knowledge, this marks the first time a fully silicon-made, chip-level LC integrated reflective load is presented.