Ka波段DMTL移相器用RF MEMS电容式并联开关研制

摘要

A MEMS capacitive shunt switch for Ka-band 5-bit distributed MEMS transmission line (DMTL) phase shifter was presented in this paper.The structural dimensions of MEMS capacitive shunt switch were roughly defined by theoretical calculation and engineering experience.The 3D electromagnetic model of the switch was established,and the structural dimensions were optimized by using HFSS software.Simulation results show that the insertion loss of the switch was lower than 0.15 dB and the isolation loss was higher than 15 dB in Ka-band.The driving voltage of the switch was 2.1 V,which was obtained from the simulation of electromechanical coupling by using CoventorWare software.After several modifications of device layout and fabrication process according to the surface micro-machining process restriction of the foundry,preliminary MEMS capacitive shunt switch process sample was obtained.Dynamic characteristics of a single MEMS switch were tested.The results show that the height pulled down by microbridge was about 2 μm with 36 V driving voltage applied.There was a big difference between the tested driving voltage 36 V and the originally designed value 2.1 V,due to the temporary structural design modification according to the process restriction of the foundry.The modifications mainly involve increasing the microbridge height,and increasing the initial distance between the microbridge (top electrode) and the bottom electrode.%本文设计并制作了一种用于Ka波段分布式MEMS传输线(DMTL)移相器的MEMS电容式并联开关.通过理论计算和工程经验,大致定义了开关的结构尺寸.采用HFSS软件建立了开关的三维电磁场模型并优化了关键结构参数.仿真表明:开关在Ka波段插入损耗小于0.15 dB,回波损耗大于15 dB.采用CoventorWare软件进行了开关的机电耦合仿真,得出其驱动电压为2.1V.为了满足流片单位表面微加工工艺的约束,对开关的设计版图和微加工工艺进行了多轮改进,得到初步的MEMS电容式并联开关工艺样品.单个MEMS开关的动态特性测试结果表明:施加36 V驱动电压时,微桥下拉的高度约为2 μm.测得的36 V驱动电压与初始设计的2.1V有较大的差异,原因在于限于流片单位的工艺约束,临时修改了结构设计,主要变化是增加了微桥的高度以及微桥(即上电极)与下电极之间的初始间距.