Novel paraffin-based 100-GHz variable capacitors for reconfigurable antennas

We report multiphysics simulation results for paraffin variable capacitors integrated with bent slot antenna to form a frequency reconfigurable structure. Paraffin is a phase change material that its solid-to-liquid transition exhibits a 15% volumetric change. In addition to its mechanical properties, paraffin is an organic low-dielectric-loss material (tan δ = 0.003, ε
_r
= 2.26 at 300 GHz) which is attractive for designing RF components at millimeter wave (mmW) band. Here, we introduce low-loss paraffin phase change material (PCM) capacitors at 100 GHz that are monolithically fabricated with antennas. A frequency reconfigurable slot antenna loaded with paraffin PCM capacitors is designed that is capable of continuous frequency tuning in the range of 97.5 GHz-103.5 GHz. The antenna has a maximum gain of 3.78 dBi and it is constant over the reconfiguration range. Actuation mechanism of the electrothermal actuator is analyzed in a multiphysics simulator. To characterize the deflection profile and the temperature distribution, it is crucial to fully couple the electric currents, heat transfer and solid mechanics. It is observed that with a 3 μm-thick actuation layer, 0.6 μm displacement can be obtained. A new fabrication method for the deposition of the thin paraffin film is developed and a fabrication process for the reconfigurable antenna is presented.