A thermally activated VO2-based attenuator with SRR structure

Abstract

To meet the requirement of blocking unwanted or interfering signals in modern communication systems, wideband phased-array antenna systems, and 5G mobile communications, we proposed a radio frequency (RF) attenuator based on a split ring resonator (SRR) that used a phase change material (PCM) vanadium dioxide (VO2). The SRR was transformed into a thermally activated attenuator by depositing a 120 nm VO2 thin film between the two gold rings of an SRR. We achieved an obvious attenuation (about 18 dB) at 3.55 GHz when the temperature increased from room temperature to 100 °C due to the dielectric constant drop and wide resistance variation of VO2 thin film during the phase change process. At the same time, we observed a hysteresis property on the S parameters due to the resistance hysteresis of VO2 during the heating and cooling process both in the theoretical and experimental results. Finally, considering the resistance of the VO2 thin film between two gold rings, we proposed a modified lumped RLC circuit model for the VO2-based RF attenuator.