A frequency tunable half-wave resonator using a MEMS variable capacitor

A frequency tunable half-wave resonator at 3GHz is presented with a MEMS variable capacitor as the tuning element. The capacitor is fabricated using the MUMPS technology provided by JDS/Cronos, and transferred to an alumina substrate by an in-house developed flip-chip process. The capacitor consists of an array of individual plates of equal areas, which are connected to a single bonding pad by springs of varying widths. This capacitor is electrostatically actuated The resulting C-V response is linear with a slope of 0.05pF/V for a wide range of actuation voltages. The MEMS device has a capacitance ratio of 3:1 for 0 to 70V bias, with a Q-factor of 140 measured at 1GHz. A half-wave tunable microstrip resonator with bias lines is designed to include this MEMS device, which exhibits linear tuning over 180MHz (6%) centered around 3GHz with a constant 3dB bandwidth of 160MHz over the entire tuning range. The power consumption of the MEMS device was measured to be negligible.