The Study For Designing And Aapplication Of MEMS Switch

RF MEMS is the abbreviation of Radio Frequency Micro-Electro-Mechanical System.It is one of the most important applications of Micro-Electro-Mechanical System(MEMS).In recent years,RF MEMS technology has become a research hotspot because of its huge potential market and broad prospects in automotive electronics,electronic communications,medical science,phased array radar and so on.RF MEMS switch is the basis components of RF MEMS,and the shunt capacitor RF MEMS switch is one of the most important branches of RF MEMS Switch.It has high isolation,low insertion loss,high linearity;however the high driving voltage and the reliability problem are the major bottleneck for RF MEMS switch.High drive voltage will cause switch failure caused by the charge injection.But driving voltage that is too low will cause a series of problems such as the reliability of beam membrane collapse,so the research for how to design a RF MEMS with low switching voltage is very significative.At the same time,down state LC series resonant frequency of shunt capacitor RF MEMS switch is generally high,the resonant frequency of fixed beam structure switching is more than 30 GHz,which limits the application of switch under K band.Increasing the down state capacitance or inductance can reduce the resonant frequency of the switch.High dielectric constant dielectric layer material is often used to increase the capacitance in down state,but this will cause serious charge injection,.therefore the increasing of the equivalent inductance of the switch can reduce the resonant frequency.By using different beam structure can change the equivalent inductance of the switch,the folded beam structure is often utilized to increase the equivalent inductance of the switch.This paper aims to design a shunt capacitor RF MEMS switch with driving voltage less than 20 V,and can be utilized in the Ku band.The electromechanical and electromagnetic simulation designing through the switch of two common parallel capacitor RF MEMS is used to ensure the final structure and the material and structural parameters of the two switch.The relationships between the insertion loss and parameters,isolation and parameters,pull-down voltage and parameters are determined.With the help of analyzing the advantages and disadvantages of these two kinds of structures,a new folded beam structure shunt capacitor RF MEMS switch is proposed,.Its pull-down voltage is 18 V in the simulation of COMSOL which is much lower than the switchs just said.The insertion loss is less than 0.105 dB in the frequency range of 12-18 GHz and the isolation is higher than 20.5dB in the same frequency range because of the the folded beam structure that reduce the LC series resonant frequency.The highest isolation is 33.5 at 12.5GHz.So this kind of switch can be utilized in the Ku band.Finally,the principle of the distributed MEMS phase shifter is studied,and a simple two bit phase shifter is realized by using the new folded beam switch.