Logan Sorenson

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This paper shows improved phase-noise performance of MEMS oscillators when the sustaining amplifier operates a lateral bulk acoustic wave AlN-on-Si resonator in the nonlinear regime. An empirical exponential-series-based model that closely describes the phase noise in nonlinearity is presented, reflecting the increased resonator filter order and the reduced(More)
We present a self-­aligned fabrication method developed for three-­dimensional (3-­D) microscale hemispherical shell resonators with integrated capacitive transducers and a center post for electrical access to the shell. The self-­aligned process preserves the axisymmetry for robust, balanced resonators that can potentially reach very high-­Q due to(More)
The effect of thickness anisotropy on the degenerate elliptical resonance modes of micro-hemispherical shell resonators (µHSRs) created using the thermal oxidation process is investigated. This anisotropy arises from the variation in wet thermal oxide growth according to the exposed crystal planes of the single-crystal-silicon hemispherical mold used to(More)
—This paper presents a new empirical exponential-series-based model that describes the measured phase-noise (PN) of a nonlinear piezoelectric MEMS oscillator. Since the order of terms in the Leeson's model can only provide at maximum-30 dB/dec slope, a model with higher order terms is proposed to determine an effective resonator quality factor (Q eff) and(More)
—Fundamental characteristics of MEMS resonators such as acoustic velocity and energy dissipation may have strong temperature and process dependencies that must be carefully compensated in applications requiring high degrees of stability and accuracy. This paper presents an overview of compensation, tuning, and trimming techniques for MEMS resonators. The(More)
—Nonlinearity of a silicon resonator can lead to improved phase-noise performance in an oscillator when the phase shift of the sustaining amplifier forces the operating point to a steeper phase-frequency slope. As a result, phase modulation on the oscillator frequency is minimized because the resonator behaves as a high-order phase filter. The effect of the(More)
This paper reports on electrical characterization of ALD-coated thermally-grown silicon dioxide micro-hemispherical shell resonators (µHSRs) with capacitive electrodes. A high aspect ratio silicon dioxide µHSR with a thickness of 2.6 µm and diameter of 910 µm, uniformly coated with 30 nm of platinum using ALD process, demonstrated Q of 19,100 at 19.17 kHz(More)
This paper presents fully-­integrated multi-­axis piezoelectric-­on-­silicon kinetic energy harvesters (KEHs) that demonstrate enhanced power output via mechanical frequency upconversion. Mechanical energy is converted to electrical energy by out-­of-­plane and in-­plane devices that are micromachined on the same substrate. The out-­of-­ plane device(More)
We report, for the first time, on the successful fabrication and operational characterization of electroplated Invar Micro-Hemispherical Shell Resonators (μHSR). The heat treatment of the samples and its effect on the quality factor (Q) of the resonators is studied. We show that thermal annealing shifts the coefficient of thermal expansion (CTE) of the(More)
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