System and circuit design for a capacitive MEMS gyroscope

In this thesis, issues related to the design and implementation of a micro-electro-mechanicalangular velocity sensor are studied. The work focuses on a system basedon a vibratory microgyroscope which operates in the low-pass mode with a moderateresonance gain and with an open-loop configuration of the secondary (sense) resonator.Both the primary (drive) and the secondary resonators are assumed to have a high qualityfactor. Furthermore, the gyroscope employs electrostatic excitation and capacitivedetection. The thesis is divided into three parts. The first part provides the background informationnecessary for the other two parts. The basic properties of a vibratory microgyroscope,together with the most fundamental non-idealities, are described, a shortintroduction to various manufacturing technologies is given, and a brief review of publishedmicrogyroscopes and of commercial microgyroscopes is provided. The second part concentrates on selected aspects of the system-level design of amicro-electro-mechanical angular velocity sensor. In this part, a detailed analysis isprovided of issues related to different non-idealities in the synchronous demodulation,the dynamics of the primary resonator excitation, the compensation of the mechanicalquadrature signal, and the zero-rate output. The use of ΣΔ modulation to improveaccuracy in both primary resonator excitation and the compensation of the mechanicalquadrature signal is studied. The third part concentrates on the design and implementation of the integratedelectronics required by the angular velocity sensor. The focus is primarily on the designof the sensor readout circuitry, comprising: a continuous-time front-end performingthe capacitance-to-voltage (C/V) conversion, filtering, and signal level normalization;a bandpass ΣΔ analog-to-digital converter, and the required digital signal processing(DSP). The other fundamental circuit blocks, which are a phase-locked loop requiredfor clock generation, a high-voltage digital-to-analog converter for the compensationof the mechanical quadrature signal, the necessary charge pumps for the generationof high voltages, an analog phase shifter, and the digital-to-analog converter used togenerate the primary resonator excitation signals, together with other DSP blocks, areintroduced on a more general level. Additionally, alternative ways to perform the C/Vconversion, such as continuous-time front ends either with or without the upconversionof the capacitive signal, various switched-capacitor front ends, and electromechanicalΣΔ modulation, are studied. In the experimental work done for the thesis, a prototype of a micro-electro-mechanicalangular velocity sensor is implemented and characterized. The analog partsof the system are implemented with a 0.7-µm high-voltage CMOS (ComplimentaryMetal-Oxide-Semiconductor) technology. The DSP part is realized with a field-programmablegate array (FPGA) chip. The ±100°/s gyroscope achieves 0.042°/s/√H̅z̅spot noise and a signal-to-noise ratio of 51.6 dB over the 40 Hz bandwidth, with a100°/s input signal. The implemented system demonstrates the use of ΣΔ modulation in both the primaryresonator excitation and the quadrature compensation. Additionally, it demonstratesphase error compensation performed using DSP. With phase error compensation,the effect of several phase delays in the analog circuitry can be eliminated, andthe additional noise caused by clock jitter can be considerably reduced

Eucalyptus cinerea: Microscopic Profile, Chemical Composition of Essential Oil and its Antioxidant, Microbiological and Cytotoxic Activities

Eucalyptus species possess anti-inflammatory, antifungal, antibacterial, and insecticidal properties. In this study, the chemical composition and biological activities of Eucalyptus cinerea essential oil (EO) and the leaf and stem anatomy were investigated. EO was extracted by Clevenger apparatus and the compounds were identified by GC/MS. The antioxidant activity was evaluated by DPPH, ABTS, and reducing phosphomolybdenum complex. Broth microdilution was used to determine antimicrobial activity. Cytotoxicity was verified against HeLa, HRT-18, and Calu-3 cells by MTT assay. The cytotoxic mechanism was studied by cell DNA content, cell cycle, and DNA fragmentation. The microscopic analyzes of the leaves and the stems were performed by light microscopy, field emission scanning electron microscopy, and energydispersive X-ray spectroscopy. The main constituent of the EO was 1,8-cineole (55.24%). The EO showed low antioxidant and antimicrobial activities. Calu-3 cells showed a significant reduction in viability with IC50of 689.79 ± 29.34 μg/mL. EO at 1000 μg/mL decreased the DNA content in Jurkat cells. In general, EO increased cell percentage in sub-G0 and S phases with concomitant reduction of cell percentage in G0/G1 and G2/M phases and provided DNA fragmentation of 29.73%. Anatomical and micromorphological features of the leaves and stems can help in the species identification and its differentiation from other Eucalyptus species

Modeling and Experimental Study on Characterization of Micromachined Thermal Gas Inertial Sensors

Micromachined thermal gas inertial sensors based on heat convection are novel devices that compared with conventional micromachined inertial sensors offer the advantages of simple structures, easy fabrication, high shock resistance and good reliability by virtue of using a gaseous medium instead of a mechanical proof mass as key moving and sensing elements. This paper presents an analytical modeling for a micromachined thermal gas gyroscope integrated with signal conditioning. A simplified spring-damping model is utilized to characterize the behavior of the sensor. The model relies on the use of the fluid mechanics and heat transfer fundamentals and is validated using experimental data obtained from a test-device and simulation. Furthermore, the nonideal issues of the sensor are addressed from both the theoretical and experimental points of view. The nonlinear behavior demonstrated in experimental measurements is analyzed based on the model. It is concluded that the sources of nonlinearity are mainly attributable to the variable stiffness of the sensor system and the structural asymmetry due to nonideal fabrication

Development of a Prototype Miniature Silicon Microgyroscope

A miniature vacuum-packaged silicon microgyroscope (SMG) with symmetrical and decoupled structure was designed to prevent unintended coupling between drive and sense modes. To ensure high resonant stability and strong disturbance resisting capacity, a self-oscillating closed-loop circuit including an automatic gain control (AGC) loop based on electrostatic force feedback is adopted in drive mode, while, dual-channel decomposition and reconstruction closed loops are applied in sense mode. Moreover, the temperature effect on its zero bias was characterized experimentally and a practical compensation method is given. The testing results demonstrate that the useful signal and quadrature signal will not interact with each other because their phases are decoupled. Under a scale factor condition of 9.6 mV/°/s, in full measurement range of ± 300 deg/s, the zero bias stability reaches 15°/h with worse-case nonlinearity of 400 ppm, and the temperature variation trend of the SMG bias is thus largely eliminated, so that the maximum bias value is reduced to one tenth of the original after compensation from -40 °C to 80 °C

Muutos henkilöstöjohtamisen näkökulmasta: talouspalveluiden uudelleenorganisoituminen osana organisaatiomuutosta

Henkilöstö on yrityksen tärkein voimavara. Työhyvinvointi ja oikeanlainen osaaminen ovat henkilöstöjohtamisen keskiössä. Toisaalta mikään ei ole niin pysyvää kuin muutos, jolloin sen johtaminen on yksi organisaation menestymisen kulmakivistä. Näiden kahden kehittäminen on tämän työn lähtökohta. Opinnäytetyön toimeksiantajalla oli taustalla merkittävä organisaatiomuutos, kun kunnan taloushallinto järjestettiin uudelleen. Opinnäytetyön tarkoituksena on kartoittaa, miten muutos johdettiin ja toteutettiin organisaatiossa. Lisäksi organisaatioon muodostui muutoksen myötä uusi palvelualue, jonka organisoituminen ja tehtävä oli myös tutkimuksen kohteena. Opinnäytetyö on tapaustutkimus, joka toteutettiin laadullisen tutkimuksen keinoin teemahaastatteluina. Aineistoa kerättiin talouspalveluiden tiimiläisiltä yksilöhaastatteluina ja kaupungin johtoryhmän ryhmähaastatteluna. Tutkimusaineisto analysoitiin teemoittain, jotka olivat muutos, organisoituminen ja talouspalveluiden tiimin tehtävä. Tutkimuksen tuloksissa esitellään muutosprosessien toteuttamisen malli. Taloushallinnon palvelualueen organisoitumisen sekä henkilöstöjohtamisen haasteisiin esitellään myös kehittämissuunnitelma opinnäytetyössä. Yhteenvetona voidaan todeta muutoksen olleen hyvä ja tehtyyn ratkaisuun oltiin tyytyväisiä organisaatiossa

Integroidun varausvahvistimen suunnittelu mikromekaanisen kapasitiivisen anturin lukemiseen

Diplomityössä on tutkittu integroidun varausvahvistimen suunnittelua mikromekaanisen kapasitiivisen anturin lukemiseen. Työn alussa esitellään kapasitiivisiin antureihin liittyvät peruskäsitteet. Tämän jälkeen perehdytään varausvahvistimen toimintaan, aluksi itsenäisenä piirilohkona, sen jälkeen kapasitiivisen anturin yhteydessä. Seuraavaksi työssä tutkitaan kapasitiivisen anturin ja varausvahvistimen muodostaman systeemin tuottamaa kohinaa. Signaali-kohina-suhteen laskemiseksi eri kohinalähteiden tuottaman kohinan suuruus esitetään varausvahvistimen tuloon redusoituna kohinakapasitanssina. Samalla etsitään keinoja eri kohinalähteiden aiheuttaman kohinakapasitanssin minimoimiseksi ja tutkitaan epäideaalisuuksien vaikutusta pienimpään saavutettavissa olevaan kohinatasoon. Tämän jälkeen esitellään varausvahvistimen toteuttamisessa tarvittavat piirilohkot, operaatiovahvistin, takaisinkytkentävastukset ja takaisinkytkentäkondensaattorit, sekä niiden mahdollisia integroituja toteuttamistapoja. Lohkojen esittelyssä kiinnitetään huomiota varausvahvistimen suunnittelussa vaadittaviin erityispiirteisiin. Työssä toteutettiin integroitu varausvahvistin 0,7 µm:n kahden metalli-ja kahden polypiikerroksen CMOS-puolijohdeprosessilla. Varausvahvistimella saavutettiin mittausten mukaan 2,85 aF:n herkkyys, kun sitä käytetään suunnittelumääritysten mukaisen anturin lukemiseen. Toteutetusta varausvahvistimesta saadut mittaustulokset tukevat työssä esitetyn teorian paikkansapitävyyttä

Fully differential electro-mechanical phase locked loop sensor circuit

Embedding a micro-machined sensing element in a closed loop, force feedback system is a technique commonly used to realise high performance MEMS (micro-electro-mechanical systems) sensors due to the advantages of better linearity, increased dynamic range and reduced parameter sensitivity. Electro-mechanical Sigma Delta modulators (EMΣΔ) have been proposed for this reason and high order loops have been shown to enjoy a good signal to noise ratio (SNR) of more than 100dB. It is also well known that achieving stability in high order EMΣΔs is a challenging task and in practice stability can be lost with large input signals or due to non-ideal effects in the circuits implemented. In this work we propose a novel dfferential frequency domain technique for closed loop control of micro-machined sensors. This method, called the electro-mechanical phase locked loop (EMPLL), uses a differential electro-mechanical phase locked loop to control and measure the detection of micro-machined sensors. We believe that EMPLLs have the potential to have significant advantages over EMΣΔs for high performance MEMS sensors. Preliminary research suggests that this novel approach will lead to significant benefits in Signal to Noise Ratio, Parameter Sensitivity, and Input Signal Range