Novel Piezoelectric Driving RF MEMS Switch Based On Composite Film

As one of the most important components in MEMS devices,RF MEMS switch is the basic component of MEMS filters,resonators,variable capacitors and phase shifters.They have potential application in radar systems,radio communications,satellite communication systems and instrumentation.Aiming at the problems of high driving voltage,slow response and poor RF performance in high-frequency of RF MEMS switches,this paper proposes a novel piezoelectric driving RF MEMS switch based on composite film.The main work of this paper can be summarized as follows:1.According to the excellent properties of Graphene,Bi_0.5Na_0.5TiO₃ and Shape Memory Polymer as well as the piezoelectric driving principle,a novel piezoelectric driving RF MEMS switch based on composite film is proposed.The basic structure and working principle of RF MEMS switch is described in detail.The piezoelectric driving force on the unit area of the composite thin film is analyzed and calculated by using the small deflection theory of thin plate bending.Furthermore,the material types of each structure of the RF MEMS switch are selected,and the mechanical properties of composite film are calculated.Simulation and analysis show that the RF MEMS switch can achieve a low driving voltage of 10.5 V;a closing time of 1.8?s and a release time of 1.75?s.The insertion loss of the switch is less than 0.6dB in the range of 0.1⁶0 GHz,the isolation is as high as-47dB at the resonant frequency of 50 GHz,and the capacitance ratio of the switch is 116.2.Optimized analysis of driving voltage and response time?closing time and release time?of the RF MEMS switch,and the following conclusions are obtained:1)The driving voltage and the release time increase with the thickness of the piezoelectric driving electrode;2)as the length of the piezoelectric driving electrode increases,the release time of the switch increases.When the length is 50?m,the release time is only 1.2?s,and the driving voltage decreases rapidly first,and then remains basically unchanged;3)As the width of the piezoelectric driving electrode increases,the change of the drive voltage and the release time of the switch are nonlinear.When the width of the piezoelectric driving electrode is 120?m,the switch reaches the minimum driving voltage of 8.3V;4)due to the phenomenon of multiple piezoelectric effect of Bi_0.5Na_0.5TiO₃ lead-free piezoelectric ceramics,with the change of the size of the piezoelectric driving electrode,the variation of RF MEMS switch closing time is nonlinear.When the piezoelectric drive electrode width is 100?m,the switch has the shortest closing time of 1.53?s.3.Optimized analysis of RF performance of the RF MEMS switch,and the following conclusions are obtained:1)The size parameter of the piezoelectric drive electrode has less effect on the RF performance of the switch;2)the width of the composite film has a significant influence on the RF performance of the switch.As the width of the composite film increases,the insertion loss of the switch also increases.When the width is 50?m,the insertion loss of the switch in the range of 0.1 to 60 GHz is less than-0.37dB.When the width is 90?m,the switch achieves a maximum isolation of about-56.54dB at a resonant frequency of 52GHz;3)the dielectric constant of the dielectric layer has little effect on the insertion loss of the switch,and the dielectric constant affects the isolation of the switch obviously,as the dielectric constant increases,the isolation of the switch increases and the resonant frequency decreases.4.The fatigue life of the RF MEMS switch is estimated by Paris law.It is estimated that the RF MEMS switch will fatigue fracture after the periodic operation about7.95?10⁸times,which will cause the switch to fail.