Superposition model for dielectric charging of RF MEMS capacitive switches under bipolar control-voltage waveforms

Bipolar control-voltage waveforms, under which the control voltage alternates between positive and negative after each cycle, have been proposed to mitigate dielectric charging in electrostatically actuated RF microelectromechanical system capacitive switches. In this study, dielectric charging under bipolar waveforms is modeled and characterized quantitatively. In general, the experimental results agree with predictions based on the superposition of unipolar charging models that are extracted under positive and negative voltages, respectively. The basic assumptions for such a superposition model are examined in detail and validated experimentally. The current analysis indicates that, while bipolar waveforms can reduce charging, it is difficult to fine tune the waveforms to completely eliminate charging.