MEMS resonators for communications transceivers
A potentially interesting use of MEMS devices is to implement them in RF transceiver designs. Integrated MEMS resonators or filters have the potential to simplify the transceiver system, improve the performance, reduce the size and lower the cost.
Several types of MEMS resonators and filters are reviewed: clamped-clamped beam resonators, free-free beam resonators and contour-mode disk or ring resonators. Each type has some advantages over traditional SAW or FBAR filters, but there are still some problems that remain.
The major focus of this dissertation is on the modeling, design, fabrication and testing of a MEMS resonator that utilizes torsional-mode vibration. The primary torsional resonance frequency is designed to be in the range of 7.5-15 MHz. The equivalent circuit is derived by analytical modeling in order to facilitate system and circuit designs. Simulations with Finite Element Analysis tools have also been performed to make comparisons with analytical modeling. Nonlinearity effects that can limit performance are also discussed. The fabrication process is then described and finally the optical testing results are compared with the derived models. The results of the testing confirm that the performance of the fabricated devices is consistent with the modeling and simulations. These results furthermore confirm that the devices meet the requirements for communications transceivers.
Potential future areas of study are outlined. This future work includes: obtaining electrical test results with a PCB and developing multiple paddle structures to either lower the input and output impedance or to serve as fully differential resonators.