RF MEMS开关吸合电压的分析

吸合电压是MEMS静电执行器的重要参数,针对RF MEMS开关,详细分析了开关在不同执行方式下的吸合电压.对于执行电压是脉冲方式而言,开关梁受迫振动,不同于准静态方式,此时使开关发生吸合的执行电压为动态吸合电压,计算表明比准静态吸合电压小8%.通过简化的弹性系数和精确的电容计算公式,详细分析了基于CPW的双端固支梁开关的准静态和动态吸合电压.分析了环境阻尼对动态吸合电压的影响,阻尼使得开关的两种吸合电压差别变小.最后分析了射频输入功率对开关吸合电压的影响,射频输入功率会降低吸合电压,如果输入功率足够大,吸合电压将会降为零,此时MEMS开关会发生自执行失效.

Analysis of Pull-In Voltage of RF MEMS Switches

The pull-in voltage of RF MEMS switches at different actuations is presented.When the actuation voltage is a pulse voltage,the movement of the switch beam is in a vibration state rather than quasi-static,so the pull-in voltage is different from the quasi-static condition and is called dynamic pull-in voltage.It is about 92% of the quasi-static pull-in voltage.Following the simple formula of the spring coefficient of a beam and the exact formula of the capacitor for the switch,the quasi-static and dynamic pull-in voltages of the clamped-clamped beam switch on CPW are analyzed,and the damping effect is also included.The damping reduces the difference between the two kinds of pull-in voltages.Finally,the influence of the RF input power on the pull-in voltage is analyzed.The input power decreases the pull-in voltage,reducing the pull-in voltage to zero at a certain power,and then making the switch self-actuate.