Design Of Low Actuated Voltage RF MEMS Capacitive Switches

RF MEMS switch has been a key element in the filed of microwave signal control. MEMS switches have several advantages over PIN diode and FET switches such as low insertion loss, high isolation, excellent compatibility with current microwave and mm-wave circuit. Because of those significant advantages mentioned above, RF MEMS switch is increasingly under focus. However, there are some disadvantages such as high-actuated voltage and so on for RF MEMS switches. The means to decrease the actuated voltage are being studied at home and abroad. In this paper, three kinds of RF MEMS switches are designed and studied in static mechanics characteristics and microwave characteristics by using IntelliSuite and CST software.The capacitive switches with the structures of serpentine supports and additional electrodes, whose actuated voltages are respectively 8V and 7V, are designed in this paper. Whereas, the actuated voltage of common capacitive switch is 14V.The result indicates that both of structures can decrease effectively the actuated voltage. Although both of them can get identical effect, increasing additional electrodes has advantages of high structure strength,good reliability and anti-quiver.The research results show that the actuated voltage of switches is influenced by material and size of membrane-bridge. The actuated voltage of Au membrane- bridge switch is higher than Al membrane-bridge switch, which is the same inch as Au membrane-bridge. The actuated voltage of Al membrane-bridge switch will decrease with the length of membrane bridge increasing on condition that its width is same. In this paper, Al membrane is chosen as upper electrode and its improved parameters are that length is 280μm and width is 160μm.The series capacitive RF MEMS switch designed in this paper can reduce insertion loss and increase isolation, which possesses an excellent microwave performance. Its isolation is higher than 20 dB from 9GHz to 16GHz and gets to maximum 35dB at 15GHz. Its insertion loss is more than 1dB.The research results show that the structures of switches designed in this paper are appropriate and can obviously reduce the actuated voltage, which provide a theoretical basis for the novel RF MEMS capacitive switch design.