Tunable RF Phase Shifters Based on Vanadium Dioxide Metal Insulator Transition

This paper presents the design, fabrication, and electrical characterization of a reconfigurable RF capacitive shunt switch that exploits the electro-thermally triggered vanadium dioxide (VO ₂ ) insulator to metal phase transition. The RF switch is further exploited to build wide-band RF true-time delay tunable phase shifters. By triggering the VO ₂ switch insulator to metal transition (IMT), the total capacitance can be reconfigured from the series of two metal-insulator-metal (MIM) capacitors to a single MIM capacitor. The effect of bias voltage on losses and phase shift is investigated, explained, and compared to the state of the art in the field. We report thermal actuation of the devices by heating the devices above VO ₂ IMT temperature. By cascading multiple stages a maximum of 40° per dB loss close to 7 GHz were obtained.