Mechanical model of electrostatically actuated shunt switch

Eriksson, A.
Uppsala Universitet

A component used in RF-MEMS systems is the electrostatically actuated shunt switch.

We show how this type of switch can be simulated using a simple mechanical FEMLAB model where electrostatic forces are modelled by a pressure load. The static as well as dynamic properties of the switch are analysed, e.g. static pull in and pull out voltages and displacements, dynamic switch up and down times and natural modes. We show how a virtual displacement constraint can be used to obtain stable static solutions for the switching characteristics of this type of device that is intrinsically unstable for actuation voltages close to the pull-in voltage. In the dynamic simulations we initially exclude damping. We then set up a more realistic multiphysics model that includes squeezed-film damping effects.

The shunt switch is a bench-mark structure that has been built and studied by several groups within AMICOM which is a European centre of excellence in the field of RF-MEMS. The FEMLAB results obtained for the shunt switch show agreement with results obtained by Ansys simulations of the same device.