Force Coupled Electrostatic RF MEMS SP3T Switch

An electrostatic RF MEMS SP3T switch using an axial force coupling is proposed. Topologically equivalent three switching membranes are coupled through flexible beams so that the deflection of one switching membrane develops mutual axial load and moment to the others (one in already ON state and the other in idle state) and helps them easily be OFF. A built-in silicon stopper amplifies an axial force and moment by restricting the displacement of coupling beams. With maintaining a low driving stiffness, about 34 % increase in the restoring stiffness was examined by the simulation. Symmetric tri-layer film stack (sandwich like) is preferred to minimize the warpage of large membrane for low driving voltage. A RF characteristics of unit switch is measured to 0.25dB-insertion loss and 51.5 dB isolation at 2 GHz with 20 V - driving voltage. Especially high RF isolation over 45 dB is achieved even at 10 GHz by using the proposed force coupled driving concept. Switching time is measured to 7.5 μs for ON switching and 3.2 μs for OFF switching.