M. Hopcroft

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In this paper, the temperature compensation of AlN Lamb wave resonators using edge-type reflectors is theoretically studied and experimentally demonstrated. By adding a compensating layer of SiO2 with an appropriate thickness, a Lamb wave resonator based on a stack of AlN and SiO2 layers can achieve a zero first-order temperature coefficient of frequency(More)
—This paper investigates the effects of dielectric charge on resonant frequency in thermally oxidized silicon resonators hermetically encapsulated using " epi-seal. " SiO 2 coatings are effective for passive temperature compensation of resonators but make the devices more susceptible to charging-related issues. We present a theoretical model for the(More)
Encapsulated micromechanical resonators have been fabricated from single crystal silicon and a method for stabilizing their resonant frequency over temperature has been demonstrated. The method uses high-frequency AC signals applied directly to the resonant structure in order to heat it. By adjusting the power of the heating signal, varying amounts of heat(More)
Micromechanical Resonator based oscillators are a promising technology for replacing quartz crystal based oscillators. In this work, we will report the effects of mechanical vibrations and bias voltage noise on the phase noise performance of electrostatic MEMS resonator based oscillators. Accurate models for both these effects are discussed along with their(More)
A digital temperature sensing technique using a complementary metal oxide semiconductor ͑CMOS͒ compatible encapsulated microresonator is presented. This technique leverages our ability to select the temperature dependence of the resonant frequency for micromechanical silicon resonators by adjusting the relative thickness of a SiO 2 compensating layer. A(More)
Silicon MEMS resonators have great potential for on-chip high frequency signal applications. This paper compares methods of sensing the temperature of an encapsulated silicon MEMS resonator and using this temperature measurement to stabilize the temperature, and hence the resonant frequency, of the resonator. The use of external Pt RTDs, integrated Si(More)
– This paper presents an improved model for SPICE-based simulation of thermoelectric structures which includes circuit elements for simulating thermoelectric Peltier and Thomson effects, and shows greatly improved accuracy over previous models where those are neglected. The complete thermoelectric model is verified by comparing with experimental results on(More)
Micromachined power sensors with operation up to 50 GHz were recently achieved in CMOS technology [1]. To improve their sensitivity and signal-to-noise ratio, while maintaining microwave performance, several design parameters must be considered, such as the number and placement of thermocouples. This paper presents experimental and analytical thermal(More)
A new microcomputer-controlled instrument that tests contrast acuity is described. It displays a range of Sloan optotype sets at five different levels between 3 and 95% contrast. The spatial contrast acuities of two groups were compared with this instrument. The first group consisted of 68 eyes of patients with posterior subcapsular cataracts whose(More)
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