The Design And Optimization Of RF MEMS Switch

RF micro-electro-mechanical system(RF MEMS) is one of the important branches of MEMS technology, it has also been the hot spot since 1990 s. RF micro-mechanical switch has merit of small size, low power consumption, and better insertion loss and isolation than traditional PIN and MOSFET switch, so it has been promising solution in radar, satellite communications, personal wireless communications, test equipment, and so on. In this thesis, an investigation of X-band shunt capacitive switch has been done.From aspects of mechanical and microwave properties of switch, a detailed analysis and research of the switch design and manufacture has been done in this paper. A static model of the switch is established and analyzed to get the impacts of geometric dimensions and material properties on the threshold voltage characteristics. Based on the proposed dynamic model, the transient response property of the switch has been studied by the tool of Matlab/Simulink. This thesis has also introduced the design method of high-frequency electromagnetic field simulation, established the equivalent circuit model of shunt capacitive switch and analyzed the influence of RLC on the insertion loss and isolation with ADS.A triple spiral RF-MEMS switch has been designed. The equivalent inductance of the top electrode is improved through the center and two sides spiral structures, leading to a lower resonance frequency and a better isolation. We concentrate on the insertion loss in the ‘on’ state and the isolation in the ‘off’ state. The key parameters which affecting on electromagnetic properties,including thickness of the dielectric layer,thickness of the air layer between top and bottom electrode and the dimension of top electrode are analyzed by Ansoft HFSS software.Results show that when the switch is in the ‘on’ state, insertion loss is less than 0.47 dB at X-bands. And in the ‘off’ state, the switch attains an isolation of more than-26.42 dB.At the center frequency,insertion loss is-0.35 dB and isolation is-31.98 dB,respectively.