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A 0–10 V bias voltage-driven liquid crystal (LC) based 0°–180° continuously variable phase shifter was designed, fabricated, and measured with insertion loss less than −4 dB across the spectrum from 54 GHz to 66 GHz. The phase shifter was structured in an enclosed coplanar waveguide (ECPW) with LC as tunable dielectrics encapsulated by a unified ground plate in the design, which significantly reduced the instability due to floating effects and losses due to stray modes. By competing for spatial volume distribution of the millimeter-wave signal occupying lossy tunable dielectrics versus low-loss but non-tunable dielectrics, the ECPW’s geometry and materials are optimized to minimize the total of dielectric volumetric loss and metallic surface loss for a fixed phase-tuning range. The optimized LC-based ECPW was impedance matched with 1.85 mm connectors by the time domain reflectometry (TDR) method. Device fabrication featured the use of rolled annealed copper foil of lowest surface roughness with nickel-free gold-plating of optimal thickness. Measured from 54 GHz to 66 GHz, the phase shifter prototype presented a tangible improvement in phase shift effectiveness and signal-to-noise ratio, while exhibiting lower insertion and return losses, more ease of control, and high linearity as well as lower-cost fabrication as compared with up-to-date documentations targeting 60 GHz applications.

A liquid crystal (LC) based tunable microstrip line (ML) phase shifter featuring high performance is presented. The experimental results show an electrically tunable differential phase up to 360° at 10 GHz with an overall insertion loss <8.5 dB. The device possesses a high figure-of-merit (FoM) of 64°/dB at 9.8 GHz and 60°/dB between 7–10 GHz. This is achieved by simultaneously considering both of the LC tuned phase and overall loss in the design. The proposed device utilizes the inverted meander ML technology to minimize its size. Taking into account the real fabrication procedure, a novel impedance matching structure is applied, and the measured return loss is considerably improved. The FoM and phase tuning property of the fabricated device as optimized are compared with the state-of-art results published recently and show better performance for both of them.