RADIO FREQUENCY SIGNAL PROCESSING WITH MICROELECTROMECHANICAL RESONATING SYSTEMS
This thesis presents a study of the dynamics and applications of a high frequency micromechanical (MEMS) resonator. Mechanical systems, which have been scaled in dimension to the micron scale, show promise for replacing electrical resonant systems, which have larger physical size and lower performance. MEMS resonators can also be integrated into a chip containing conventional field effect transistors. A process incorporating both frequency dependent resonant systems as well as analog and digital electronics will enable all hardware in a communication architecture to be placed on a single silicon chip. In this study, a micron-sized circular membrane, suspended in the middle and clamped on the periphery, forms the basis of the resonant mechanical system. A small degree of curvature is fabricated into the resonator, which serves to stiffen the device and hence increase the frequency range. A microheater, defined in proximity to the resonator, is used to induce motion in the membrane. The frequency dependent response of the membrane is then detected through either interferometric or piezoresistive techniques. Resistive actuation and detection allow the membrane and actuators to be fabricated into a single plane of silicon, facilitating integration of the complete MEMS system. It is demonstrated how both the resonators and transducers can be implemented into two CMOS processes. Both designs incorporate the mechanical system as well as the solid-state electronics for output signal detection into a single fabrication process. Finally, the dynamics of the MEMS resonator, both in the linear and non-linear regime, are explored. The micron-sized mechanical system is demonstrated to perform several types of signal processing that are critical for wireless communication architectures. These studies shed new light on how the nonlinear dynamics of these systems may be characterized and harnessed for new applications.
microelectromechanical systems; MEMS; radio frequency; signal processing; thermal mechanical coupling; nonlinear oscillations
dissertation or thesis