chapter  5
50 Pages

RF-MEMS Switches Operating at Microwave and mm-Wave Frequencies

It is essential to define a design optimization process aimed to achieve three distinct objectives, namely, high power-handling capability, lower pull-in voltages between 10 and 40 V, and short switching times ranging between 1 and 5 ms. Impact of nonlinear effects generated by the MEMS capacitive switches will be investigated. Because most of the MEMS devices or circuits operate at power levels of 1-1000 mW, linearity aspect is a critical parameter to prevent distortions and interchannel interferences. Because RF-MEMS switches have potential applications in wireless communication systems, electronic warfare (EW) equipment, and missile tracking radar incorporating electronically steering-phased array antennas where phase distortion is not acceptable. A fixed-beam RF-MEMS shunt switch and a cantilever RF-MEMS series switch (Figure 5.1) will be selected to investigate the adverse effects of nonlinearity [1]. MEMS switches are characterized by an upstate capacitance, which varies as a function of bridge height. The cantilever beam can be moved using an ES force between the bridge and the bottom electrode, which is

generated by the ES actuator. The upstate capacitance is affected by the nonlinear effects such as intermodulation (IM) products generated by the RF power. Data presented in latest publications reveals that these distortions are generally small and can be neglected. This is a distinct performance advantage of MEMS devices as compared to other switching devices using PIN-diodes, metal-semiconductor-fieldeffect transistor (MESFET), varactor diodes, or ferroelectric films.