| This dissertation investigates new designs and techniques to improve the performance of vibrating micromechanical signal processors for wireless communication applications, primarily focusing on ring-type resonators. The thesis discusses the theoretical design, simulation, fabrication, and characterization of such devices, with a purpose of providing a new path towards further lowering the motional impedance of micromechanical resonators.;Vibrating polysilicon micromechanical ring resonators, utilizing a unique extensional wine-glass mode shape to achieve lower impedance than previous UHF resonators, have been demonstrated at frequencies as high as 1.2GHz with a Q of 3,700, and 1.52GHz with a Q of 2,800. The 1.2-GHz resonator exhibits a measured motional resistance of 1MO with a dc-bias voltage of 20V, which is 2.2x lower than measured on radial mode disk counterparts at the same frequency. The extensional wine-glass resonator, which integrates the advantages of the extensional vibration mode, nonintrusive side supports and a ring geometry to achieve high frequency, high Q, and impedance tailoring capability, presents itself as another attractive candidate for miniaturization of transceivers.;This dissertation also develops techniques to eliminate undesired resonance modes and thus, solves one of the most disturbing issues with ring-type resonators. Through a combination of suspension-derived damping, electrostatic force tailoring, and sense electrode current cancellation, spurious modes at 406.7, 418, and 419 MHz, normally observed near the resonance of a 415-MHz extensional wine-glass mode resonator have been successfully suppressed, as have all spurious modes within at least a 50% bandwidth region around the resonant frequency. These improvements pave the way for the use of these devices in micromechanical oscillator and filter circuits targeted for future wireless transceivers.;A 217-MHz filter structure, composed of two mechanically-coupled ring resonators with solid dielectric gaps, has been investigated to prove the design concept including a notched coupling to achieve a narrow passband as small as 0.02% percent bandwidth. The fully differential drive/sense technique is employed in the filter measurement, where a large stopband rejection of 25dB is measured due to the significant reduction of severe parasitic feedthrough currents. This result verifies the efficacy of differential micromechanical filter design. |
