低驱动电压电容式RF MEMS开关结构设计优化

Mechanical Topology Optimization for Low Threshold Voltage Capacitive RF MEMS Switches

RFMEMS开关将成为微波、高频信号控制的关键器件。针对其驱动电压过高,不能满足现代通信系统低电压的要求,推导了电容式RFMEMS开关驱动电压的理论公式;基于降低开关柔顺结构的弹性系数、驱动电极上极板与可变电容上极板分离的思路,优化设计了三种具有不同的连接梁和支撑梁结构形式的开关微桥柔顺结构。第一种结构为驱动电极板和电容上极板之间以双直梁连接;第二种结构以一组弹性折叠梁代替结构一中的双直梁;第三种结构是在结构二的基础上,改变了起支撑作用的弹性折叠梁的方向。使用MEMS CAD软件CoventorWare对开关结构进行了机电耦合仿真,仿真结果表明开关的驱动电压小于3V。

A RF MEMS switch will be the key element in the field of the microwave and mm-wave signal control. A challenge of the practicability is that the threshold voltage is too high to meet modern low voltage communication systems. Formula for the threshold voltage of the capacitive RF MEMS was deduced. Based on the idea to reduce the elasticity coefficient of the compliant mechanism and to separate the upper pull-down capacitor plate from the upper variable capacitor plate, three optimized switch compliant mechanism topologies were designed with different link-beam and suspend-beam assemblies. In the first optimized topology, two straight beams were used to connect the separated upper pull-down capacitor plate and upper variable capacitor plate. In the second one, folded beams were used to replace those straight beams in the first one. In the third one, the directions of the folded beams suspending the bridges were perpendicular to those in the previous two cases. CoventorWare, a MEMS CAD software, was utilized to simulate the electro-mechanical characteristics. Simulation results demonstrate that the threshold voltages of the switches are lower than 3 V.