Design and Characterisation of RF-MEMS Components

Design and characterisation of RF MEMS devices Miniaturisation of IC technologies has enabled the performance of electronic systems to progress by leaps and bounds over the past couple of decades. The ability to create ever smaller electrical components in astoundingly massive amounts has inspired researchers to extend IC manufacturing techniques towards the fabrication of miniature devices with mechanical functionality. This effort has resulted in a large variety of microelectromechanical systems (MEMS) or microsystems that are used for sensing pressure, acceleration, angular rate, the presence of chemical or biological substances, as well as for actuating optical or electrical switches, microfluidic pumps and valves, micromirror arrays and a host of other micromachines. Applications of microsystems in RF circuits are usually gathered under the acronym RF MEMS, which are the main topic of this dissertation. The first chapter of this text briefly introduces the origins of microfabrication and gives a topical review of RF MEMS devices that have been developed to date. As electrostatic actuation is commonly used in many microsystems for RF as well as for other applications, the second chapter deals with mechanical modelling of electrostatic actuators. Several aspects of the operation of electrostatic actuators are investigated: spring constants, CV characteristics, influence of stress and stress gradient. Experimental characterisation results are presented and compared with modelling results. In the third chapter, the influence of environmental changes on the performance of electrostatic actuators is investigated. The influence of temperature changes is studied, as well as the impact of ambient pressure on the damping and switching time of parallel-plate actuators. Measured damping properties are used for hermeticity evaluation of wafer-level packaging. In addition, the influence of mechanical shock impulses is analysed and empirically verified. Chapter four covers the RF properties of the devices that are modelled and characterised in the previous chapters. The performance of capacitive series and shunt switches is measured and component models are fitted onto the measured results. The performance of the devices is then optimised by combining series and shunt switches, and by integrating additional inductance in the suspension beams of the devices. Finally, the devices are combined into an antenna switch module featuring 6 RF input ports and a common antenna port.status: publishe