A novel comprehensive approach to feedback control of membrane displacement in radio frequency micro-electromechanical switches

In this work, a novel feedback control technique for MEMS switch membrane is presented. Due to difficulties associated with measurement of membrane displacement, the capacitor current is used as the controller feedback signal. System identification is utilized to construct a transfer function relating Membrane displacement to capacitor current. Accelerating electrostatic pulse is utilized to accelerate the membrane at the start of the closing stage while a two degree-of-freedom, proportional-integral-derivative control is implemented and tuned to attain soft landing of the membrane on the electrode. The proposed technique eliminates membrane impact bouncing, reduces switch closing time, and improves the durability and reliability of the switch. The technique also improves the membrane transient response during pull-in and release stages. Simulation of the structural model dynamics shows good agreement with experimental results. The proposed technique achieved 200% increase in switch closing speed, 100% reduction in impact bouncing, 75% reduction in release overshoot, and an average of 55% reduction in membrane settling time at zero electrostatic voltage. The proposed model is benchmarked against experimental data, while the control technique is validated via simulation.