Effect of Air Gap on the Performance of a Capacitive Shunt RF MEMS Switch and a New Design Approach for Improved Performance

 Abstract— A Fixed - Fixed RF MEMS switch has been simulated for various air gaps and the variation of the electrical performance in accordance with the air gap has been studied. The switch was simulated and the pulls in voltages for different air gaps were practically determined by electrostatic analysis using IntelliSuite software. Subsequently, the theoretical values were determined analytically and the values were found to be closely matching with less than 2% error. The pull in voltage was found to be 9.78V for an air gap of 1.5 µm and increased to 51.36V for an air gap of 4.5 µm. However, the insertion loss was at -0.5522 dB for an air gap of 1.5µm at 60 GHz and smaller insertion losses was achieved only with larger air gaps. These investigations showed that large compromise on electrical performance is required for lower pull in voltage which is essential for the use of these switches in mobile applications. Considering these difficulties the authors have proposed a varying section fixed - fixed beam switches that can be designed to give lower pull in voltages even for larger air gaps. Therefore these proposed switches can ensure superior electrical performance along with low pull in voltages.