Review of Mechanical Modelling of Fixed-Fixed Beams in RF MEMS Switches

Abstract

This paper addresses mathematical analysis of the mechanics involved in RF MEMS Switch. The fixed-fixed beam undergoes deflection in y direction when a force is applied onto the beam. Fixed-Fixed beams are used due to there ease of high spring constant and ease of manufacturing. The first section of paper deals with mechanical analysis of the beam i.e. derivation of reaction forces and reaction moment. The later section of paper deals with the derivation of spring constant of fixed-fixed beam. Along with the fast development of the automotive electronics technology, the wireless communication technique on vehicles has huge market potential. This paper takes the cantilever beam MEMS switch as an example to discuss mechanical principle and function simulation of the RF MEMS switch used in Vehicle-carried radio frequency communication. The increasing demand for low loss, high Q devices for high frequency applications has led to the development of MEMS components in the RF domain. RF MEMS has evolved over the past decade and it has emerged as a potential technology for wireless, mobile and satellite communication and defence applications. Extensive research has been carried out to identify and overcome the limitations of RF MEMS technology for replacing PIN or FET based switches for low-loss applications. The main advantage of this technology is that the devices can be manufactured by processes similar to that of VLSI and the advancement of VLSI technology has helped in the realization of many sub millimeter-sized parts to provide RF functionality. The spring constant for fixed-fixed beam is modelled in two parts - One due to stiffness of bridge which accounts for material properties and other due to residual stress. This paper deals with the spring constant due to stiffness of bridge. A comparative study of various materials with different young's odulus is also carried out.