The present authors have earlier reported the employment of varying section fixed-fixed beam for achieving lower pull-in voltage with marginal fall in restoring force. Reducing Young’s modulus also reduces the pull-in voltage but with lesser degree of reduction in restoring force. Composite beams are ideal alternatives to achieve decreased Young’s modulus. Hence new varying section composite fixed-fixed beam type RF MEMS switch has been proposed. The main advantage of this RF MEMS switch is that lower pull-in voltages can be achieved with marginal fall in stiction immunity. Spring constant of the proposed switch has been obtained using simulation studies and it has been shown that the spring constant and therefore the pull-in voltage () can be considerably reduced with the proposed switch. Simulation studies conducted on the proposed switch clearly demonstrate that the pull-in voltage can be reduced by 31.17% when compared to the varying section monolayer polysilicon fixed-fixed beam. Further this approach enables the designer to have more freedom to design lower pull-in voltage switches with improved stiction immunity. 1. Introduction At present RF MEMS devices are gaining popularity due to their appreciable performance at RF and microwave frequencies unlike their semiconductor counterparts and this has led to the growth of RF MEMS switching devices which are much closer to ideal switches [1–12]. However, most micromachined switches use electrostatic pull-in [13, 14] for the control of switching action and their main drawback is high pull-in voltage () against the current trend of using low voltage power supplies which makes them useless in miniaturized mobile systems. In the last decade researchers worldwide have been focusing their effort to design switches with lower pull-in voltage. Three different approaches have been employed generally by researchers, namely, reducing the air gap, increasing the electrostatic actuation area, and decreasing the stiffness constant by either increasing the length or reducing the width [3, 15–19]. Among these three, the third approach is widely attempted. This approach depends on decreasing spring constant of the beams by increasing the beam length () and/or reducing the beam width () but ensuring that the beam does not show the tendency to stiction with the surface. In other words reduction in pull-in voltage must be achieved without any serious loss of restoring force . Hence it becomes necessary to find an approach where pull-in voltage is reduced but with minimum loss of . The present authors have earlier
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