The determination of the pull-in voltage from the condition of bridge stability

An analytical expression for the pull-in voltage is deduced for an RF micro-electromechanical system (MEMS) switch, by tacking into account the presence of a dielectric layer deposited on the coplanar waveguide. The model allows investigation of the influence of the dielectric permittivity and the geometry of the device on the displacement d of the bridge and on the pull-in voltage. A comparison of the experimental data and the simulated data gives indication about the best way to estimate the pull-in voltage. The difference between the value obtained for the pull-in voltage, when the contribution of the dielectric layer is taken into account and the value of the pull-in voltage obtained by neglecting the presence of the dielectric layer is significant indicating that the presence of the dielectric layer cannot be neglected.