Design and simulation of a wide-range variable MEMS capacitor using electrostatic and piezoelectric actuators

In this paper, we present a new structure of a micromachined tunable capacitor using a combination of piezoelectric and electrostatic parallel-plate actuators. Electrostatic parallel-plate capacitors have a low capacitive tuning ratio due to the “pull-in” instability. Therefore, to increase the capacitive tuning ratio, an electrostatic parallel-plate actuator, as well as a piezoelectric two-directional actuator, was used in this work. To verify the theoretical results, they were compared to the simulation results achieved by COMSOL and HFSS software. According to the analytical and simulation results, the proposed structure has a maximum capacitive tuning range of 2180% by applying 5.6 V for the electrostatic parallel-plate actuator and ± 8 V for the piezoelectric actuator.