MEMS-based Variable Capacitor for Millimeter-Wave Applications

Abstract

We have demonstrated a MEMS-based variable capacitor with outstanding RF performance acceptable for millimeter-wave applications. Actuators were used to move the MEMS capacitor plate vertically to change the air gap between the MEMS plate and the signal line of a coplanar waveguide (CPW). The air gap change resulted in a capacitance change with a ratio of 2.7: 1. The MEMSbased capacitor achieved a very impressive quality factor (Q) that was close to 300 at 0.1 pF and 10 GHz. In addition, the capacitance showed no resonance and the equivalent resistance was less than 0.5 R in the frequency range up to 40 GHz. The assembly technology and the RF and actuator designs critical to the capacitor demonstration are discussed.