Piezoelectric MEMS Varactor for Silicon-Based QMSIW Filter for Ka Band Applications

A piezoelectric MEMS varactor is designed to work for Ka band application. Piezo MEMS varactor is used as a tuning structure to tune the frequency of a Quarter Mode Substrate Integrated Waveguide resonator working at Ka band. Piezoelectric MEMS varactor is placed over the QMSIW resonator. The QMSIW resonator is designed over the high-resistive silicon having dielectric constant εr = 11.7 whose substrate thickness is of 254 μm. The gap between QMSIW top layer and piezo MEMS structure is 44.4 μm. Piezoelectric MEMS varactor structures with different thicknesses are simulated and compared. The actuation voltage of −20 V is applied to the top layer to deform the piezo MEMS structure to 4.8 μm in the upward direction. With the deflection achieved by piezo MEMS structure the capacitance between the QMSIW and the MEMS structure is varied thereby changing the resonant frequency. With maximum deflection, 100 MHz of tunability is achieved from 26.42 to 26.32 GHz at lower passband frequency to 30.15–30.05 GHz at the higher pass band.