MEMS Variable Capacitor Actuated with an Electrically Floating Plate

A MEMS variable capacitor with a new actuation principle was proposed and demonstrated. It utilizes electrostatic actuation of an electrically floating plate, which is advantageous in terms of Q-factor by eliminating spring resistance in an RF signal path. We achieved a tuning ratio of 41% with the control voltage of 5.5 V and a measured Q of 26.7 at 5 GHz (C=0.37 pF), which showed 131% increment of the Q from the conventional tunable-gap capacitor.