Dynamic Simulations of a Novel RF MEMS Switch

We present a dynamic analysis of a novel RF MEMS switch utilizing the dynamic pull-in phenomenon. We study this phenomenon and present guidelines about its mechanism. We propose to utilize this phenomenon to design a novel RF MEMS switch, which can be actu- ated by a voltage load as low as 40% of the traditionally used static pull-in voltage. The switch is actuated us- ing a combined DC and AC loading. The AC loading can be tuned by altering its amplitude and/or frequency to reach the pull-in instability with the lowest driving voltage and fastest response speed. The new actuation method can solve a major problem in the design of RF MEMS switches, which is the high deriving voltage re- quirement. In this work, we propose a novel RF MEMS switch that can be actuated by a voltage load as low as 40% of the static pull-in voltage. The new actuation method is based on the dynamic pull-in phenomenon, in which the switch is brought to pull-in by a voltage lower than the static pull-in voltage. The dynamic pull-in phenomenon has been previously reported and analyzed for switches actuated by a step voltage (2,3) and various ramping rates (2). Both studies (2,3) indicate that the dynamic Figure 1: A schematic of an electrically actuated mi- crobeam. pull-in voltage can be as low as 91% of the static pull- in voltage. In the presence of squeeze-film damping, the dynamic pull-in voltage is shown to approach the static pull-in voltage (3). Here, we propose to actuate the switch using a combined DC and AC loading. The AC loading can be tuned by altering its magnitude or frequency to reach the pull-in instability with the lowest driving voltage and fastest response speed. In (4-7), we presented a model, which predicts the static pull-in phenomenon. In (8), we utilized pertur- bation methods to predict the dynamic behavior of res- onators undergoing small motions near the equilibria. In (6,7), we developed a reduced-order model to simu- late the static and dynamic behaviors of resonators and switches undergoing small or large motions. In this pa- per, we use the reduced-order model in (6,7) to simu- late the dynamic behavior of the proposed RF MEMS switch. We utilize a shooting technique (9) and long- time integrations of the equations of motion to predict periodic motions. This approach can be applied to a wide range of loadings and initial conditions, and hence it can be used to study the 'global' dynamics of switches (unlike the model presented in (8), which is based on perturbation methods and applicable for small motions near the equilibria). We use the global approach to demonstrate the new actuation method.