Structural Design And Finite Element Simulation Of MEMS Filter

Tunable filters are important components in optical communication systems,but they are subject to many restrictions due to their large size,narrow tuning range,slow response,low resolution and high cost.In recent years,MEMS-based F-P tunable filters have been attracted more attention because of their good optical performance.In this paper,the optimal design of the array MEMS tunable F-P filter is studied by theoretical research,structural design and simulation analysis.The main contents include:Firstly,the basic theory of MEMS devices is studied.The microstructural effects of microstructures are analyzed from the aspects of geometrical structure,rigid body dynamics and physical parameters.It is concluded that the design of MEMS devices should be a large surface area and volume ratio,and reducing the size can effectively lower the power consumption.Also,the effect of the electrostatic drive on the suction is studied,and it is showed that the maximum displacement of the electrode plate before pulling up is one third of the initial gap.And,according to the Reynolds equation,the formula of the damping coefficient of the parallel rectangular plate is deduced.Then the static mechanics model,the support beam model and the dynamic model of the MEMS tunable filter are established,and the structure is analyzed by steady state and transient analysis.The effect of cantilever beam size on the electrostatic driving performance is studied.It is concluded that the equivalent stiffness coefficient of the cantilever beam has a direct effect on the electrostatic driving characteristic,and which is calculated from the theoretical and finite element simulation.The difference between the calculation and the simulation results is less than 10%.Thus,the final use of I-beam instead of L-beam improves the design of the support beam.The dynamic model of the system is established in order to study the transient response of the filter.It is concluded that the pressure of the package has an important effect on the transient response.Compared with 1000 Pa,100Pa and 10 Pa,the filter response speed is the fastest when the packing pressure is 10 Pa.Finally,the finite element analysis of MEMS filter is carried out.The steady-state response of the filter is studied,and the electrostatic-structural coupling simulation of the filter is carried out.The finite element simulation results are consistent with the theoretical results.Simulated temperature load and when the temperature changes,the silicon plate and the optical film in the lens structure cause structural deformation due to thermal expansion mismatch.It will change the F-P cavity length,which will affect the filter wavelength.Therefore,how to solve the issues about heat sensitive remains to be studied.In addition to the modal analysis,the results show that the first two modes of modal frequency are in a reasonable range.Therefore,the device will not be subject to external interference.