Layered axial force coupled membrane based metal contact single-pole quad-throw RF MEMS switch: design, RF performance and mechanical modeling

RF MEMS is a perfect candidate to replace the conventional switches used for microwave frequency. Most of the RF MEMS switches developed generally concentrate on single-pole single-throw based configurations and limited work is reported on switches based on single-pole multiple-throw. This paper reports an RF MEMS single-pole quad-throw (SPQT) switch design and modeling utilizing an axial force coupling mechanism among membranes. The proposed novel SPQT structure consists of twin pair switching membranes coupled using flexible beams. The primary advantage of such a mechanism is to increase isolation as when one switching membrane is pulled down to the ON-state, there develops an axial force on the other and hence it is turned to a better OFF state. The gap on other port increases. Hence, this enables the coupled pair of switches to achieve simultaneously a low actuation voltage, high isolation. The displacement of coupling beams is restricted by a silicon stopper and hence further amplifies the axial force. The designed 3-layer stack (Silicon Nitride/Gold/Silicon Nitride), minimizes the warpage of large membrane. The insertion loss and isolation among throws of the SPQT are simulated to be better than 0.09 and 53 dB at 2 GHz, respectively. The voltage required for actuation is 12 V while the SPQT switch has a compact area of 1 mm x 0.7 mm.