| This dissertation explores new designs and techniques to improve the performance of micromechanical signal processors for communications applications, mainly focusing on composite array resonators and filters. The thesis discusses the design, simulation, fabrication, characterization, and verification of polysilicon versions of such devices, with a particular purpose of achieving lower resonator and filter impedances. A brief review of popular transceiver architectures is given to illustrate the advantages offered by MEMS technology in communication systems.; Towards attaining better performance, second- and third-mode polysilicon free-free beam microresonators have been demonstrated at frequencies up to 102MHz with Q's on the order of 11,500. Via strategic design of electrodes and support structures, these resonators attain better performance than their fundamental-mode counterparts. In addition, transverse-mode square plate microresonators have been demonstrated at similar frequencies with Q's of 18,000 to offer greater phase flexibility between input and output signals.; Substantial reductions in vibrating micromechanical resonator series motional resistance RX have been attained by mechanically coupling and exciting a parallel array of poly-silicon square microresonators. Using this technique with seven resonators, an effective RX of 480O has been attained at 70MHz, which is more than 5.9X smaller than the 2.82kO exhibited by a single square resonator, and all this is achieved while maintaining Q > 9,000. This method for RX-reduction does not sacrifice linearity, and thereby breaks the RX versus dynamic range trade-off often seen when scaling.; By using mechanically-coupled square resonator arrays as "composite" resonators, the impedance of a 68.1-MHz, capacitively-transduced micromechanical filter has been lowered to point of allowing L-network-aided matching to antenna impedances, while also exhibiting 2.7dB insertion loss for a 0.28% bandwidth. The use of composite arrays also reduces filter bandwidth---an important feature for channel-select applications.; Finally, a new method for realizing a fourth-order micromechanical filter response using only a single, mass-loaded, flexural-mode disk resonator has been used to demonstrate a 20.26-MHz Butterworth filter with a tiny 0.03% bandwidth and 2.56dB of insertion loss. The basic design technique uses orthogonal mode-splitting and recombining to achieve a parallel-class filter that dispenses with the need for multiple resonators and coupling links in previous filters. |
