Paraffin-Based RF Microsystems for Millimeter-Wave Reconfigurable Antenna

We report the design, fabrication, and testing of a millimeter-wave (mmW) reconfigurable antenna based on paraffin phase change material (PCM) variable capacitors. Paraffin is a low-loss dielectric (
$\tan \delta =6.6 \times 10^{-4}$
at 100 GHz) that undergoes a 15% volumetric change through its solid–liquid phase change. A radio frequency (RF) electrothermomechanical actuator is monolithically integrated with a slot antenna in order to achieve a frequency reconfiguration at 100 GHz. RF performance is verified using on-wafer probing and compared with full-wave and multiphysics simulations. The measured bandwidth of 94.1–104.1 GHz and the resonance frequency shift of 6.8 GHz are achieved. With a maximum voltage of 5.4 V, paraffin-based electrothermomechanical actuators have a maximum displacement of 1.4
$\mu \text{m}$
, which yielded a 15.3% capacitance change. Using a fully coupled multiphysics simulation, switching time of the actuator is estimated as 5.7 ms. This work is the first demonstration for the new class of low-loss reconfigurable RF microsystem that will enable applications, including wireless communication, radars, and biomedical sensing.