High-Q, tunable-gap MEMS variable capacitor actuated with an electrically floating plate

Abstract

We proposed and developed a new MEMS variable capacitor that resembles the tunable-gap capacitor at first glance, but provides much better Q-factor thanks to reducing series resistance by the elimination of mechanical spring in the RF signal pathway using a new actuation method of moving electrically floating plate. The fabricated variable capacitor showed almost 200 % increment of Q- factor from the conventional tunable-gap capacitor. In addition, a variable capacitor array connected in parallel with four capacitors for larger capacitance was fabricated and measured. We achieved a tuning ratio of 41 % and (Q -factor of 34.9 at 5 GHz for the single capacitor and the tuning ratio of 29 % and (Q -factor of 39.8 at 1 GHz for the capacitor array.