Microelectromechanical Systems for Wireless Radio Front-ends and Integrated Frequency References.

Microelectromechanical systems (MEMS) have great potential in realizing chip-scale integrated devices for energy-efficient analog spectrum processing. This thesis presents the development of a new class of MEMS resonators and filters integrated with CMOS readout circuits for RF front-ends and integrated timing applications. Circuit-level innovations coupled with new device designs allowed for realizing integrated systems with improved performance compared to standalone devices reported in the literature. The thesis is comprised of two major parts. The first part of the thesis is focused on developing integrated MEMS timing devices. Fused silica is explored as a new structural material for fabricating high-Q vibrating micromechanical resonators. A piezoelectric-on-silica MEMS resonator is demonstrated with a high Q of more than 20,000 and good electromechanical coupling. A low phase noise CMOS reference oscillator is implemented using the MEMS resonator as a mechanical frequency reference. Temperature-stable operation of the MEMS oscillator is realized by ovenizing the platform using an integrated heater. In an alternative scheme, the intrinsic temperature sensitivity of MEMS resonators is utilized for temperature sensing, and active compensation for MEMS oscillators is realized by oven-control using a phase-locked loop (PLL). CMOS circuits are implemented for realizing the PLL-based low-power oven-control system. The active compensation technique realizes a MEMS oscillator with an overall frequency drift within +/- 4 ppm across -40 to 70 °C, without the need for calibration. The CMOS PLL circuits for oven-control is demonstrated with near-zero phase noise invasion on the MEMS oscillators. The properties of PLL-based compensation for realizing ultra-stable MEMS frequency references are studied. In the second part of the thesis, RF MEMS devices, including tunable capacitors, high-Q inductors, and ohmic switches, are fabricated using a surface micromachined integrated passive device (IPD) process. Using this process, an integrated ultra-wideband (UWB) filter has been demonstrated, showing low loss and a small form factor. To further address the issue of narrow in-band interferences in UWB communication, a tunable MEMS bandstop filter is integrated with the bandpass filter with more than an octave frequency tuning range. The bandstop filter can be optionally switched off by employing MEMS ohmic switches co-integrated on the same chip.PhDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/109069/1/zzwu_1.pd

Enhancement of an indium phosphide resonator sensor microsystem through the development of an adaptive feedback circuit and electrospray deposition

Cantilever resonator sensor enhancement through the development of an adaptive feedback circuit and the use of electrospray deposition is presented. The feedback system adapts to a wide range of resonators by implementing a hill climbing algorithm, locking onto the cantilever's resonance condition. Eight different cantilever-based sensors (Length=40-75μm), resonating at 201.0kHz to 592.1kHz, with a minimum standard deviation of 11.8Hz, corresponding to a mass resolution limit of 123fg for the device, have been dynamically detected using a single circuit. Electrospray deposition of thin-films on multiple substrate materials and released microstructures has been performed. An average deposition rate of 9.5±5nm/min was achieved with an average surface roughness of 4.5nm on a 197nm thick film. This technology will enable a post-processing method for depositing absorbing layers for sensing applications. With the development of these two technologies, the practical functionality of a chip-scale sensor microsystem will be more readily realized

Superhydrophobic BIOMEMS sensor arrays: development of actuation and readout electronic strategies

2012/2013La tecnologia dei sistemi micro-elettro-meccanici (MEMS) ha dimostrato d’avere grandi potenzialità in molti campi, in particolare nei sistemi bio-medicali. Essa si basa infatti su processi di fabbricazione ad altro volume produttivo, permettendo una considerevole riduzione dei costi per dispositivo. Un ulteriore beneficio di questa tecnologia risiede nella possibilità di dimensionare i dispositivi fino a raggiungere l’ordine del submicron, così da consentire l’integrazione e il monitoraggio in tempo reale di sistemi sensibili a biomarker di tipo medicale e biologici. Tra gli obiettivi futuri dei MEMS biomedicali (BioMEMS) vi è la realizzazione di dispositivi in grado di interfacciarsi direttamente con il paziente e definirne lo stato di salute grazie alla rilevazione del livello di centinaia di diversi biomarker (siano essi chimici o fisici). La medicina assumerebbe in questa visione una configurazione ad personam nella quale al paziente verrebbe prontamente somministrato un quantitativo di medicinale adatto alle risposte del suo organismo. A tale scopo i dispositivi MEMS devono essere in grado di effettuare analisi multiple operando in un ambiente liquido. Tuttavia è proprio l’ambiente liquido a comportare la riduzione di sensibilità e, quindi, di performance dei sensori MEMS. La presente ricerca si pone lo scopo di sviluppare nuovi sistemi elettronici di misurazione e attuazione di due distinte tipologie di BioMEMS risonanti operanti in liquido, i cantilever e i pillar. In particolare verrano trattati tre argomenti: la realizzazione di setup ottici per applicazione dei MEMS in liquido ed in aria, la progettazione di sistemi elettronici di attuazione e lettura di singoli pillar nel loro comportamento in frequenza e lo sviluppo di un software LabVIEW in grado di programmare un FPGA ed ottenere un PLL digitale da impiegarsi nell’analisi in tempo reale del comportamento in frequenza di RF-MEMS. Il primo progetto è stato sviluppato in collaborazione l'Università di Kaiserslautern (Germania) e prevedeva la realizzazione di sistemi microfluidici e setups ottici, interfacciati in modo tale da permettere la rilevazione della risposta in frequenza di molteplici MEMS operanti in parallelo. Nel secondo progetto l’obiettivo era la realizzazione di un sistema elettronico in grado di integrare in un unico dispositivo i sistemi di attuazione e lettura dei pillar. In particolare siamo stati in grado di modulare l’ampiezza di risonanza dei nostri dispositivi risonanti mediante l’applicazione della forza di polarizzazione Kelvin mentre lo sviluppo del sistema di lettura richiede ulteriore lavoro di indagine. Infine, nell'ultimo progetto è stato realizzato un sistema PLL digitale con 10 MHz di banda passante utilizzando la tecnologia della National Instruments (FlexRIO NI5781R). Mediante questo PLL si è potuto identificare la frequenza di risonanza di diverse tipologie di MEMS e se ne è seguite le variazioni in tempo reale . Le attività di ricerca sperimentale sono state eseguite presso il laboratorio CNR- IOM a Trieste.XXVI Ciclo198

Ultra-Low-Power Wake-up Clock Design for SoC Applications

This thesis studies how to design an ultra-low-power wake-up clock circuit for SoCapplications that essentially consists of a resistor based reference circuit, switched-capacitor branch, an ultra-low-power amplifier, a VCO and a non-overlapping clockphase generator circuit. The circuit is designed in 180-nm CMOS technology usingCAD software for circuit design, layout design, pre and post-layout simulations.At first, a brief study of different clock-generation circuit architectures is made,wherein their merits and de-merits are discussed. This is followed by a study ofan ultra-low-power amplifier, ring-oscillator-based VCO, non-overlapping clockcircuits, the bias generation circuit and the current reference circuit. Additionally,a reference current chopping technique that further improves temperature stabilityis also described. Later, the report discusses the design and simulations of theactual implementation. Analysis of the design with regards to power consumption,temperature stability and layout area are carried out. The circuit operates at8.254kHz consuming 70.4nW with a temperature stability of 7.35ppm/◦C in thetemperature range of -40◦C to 75◦C. The final layout takes an area of 0.153mm2.The final design is analysed for its functionality at various process, voltage andtemperature corners. Future improvements in the current design are also discussedat the end of this report

Characterization, Control and Compensation of MEMS Rate and Rate-Integrating Gyroscopes.

Inertial sensing has important applications in navigation, safety, and entertainment. Areas of active research include improved device structures, control schemes, tuning methods, and detection paradigms. A powerful and flexible characterization and control system built on commercial programmable hardware is especially needed for studying mode-matched gyroscopes and rate-integrated gyroscopes. A gyroscope can be operated in a mode-matched rate-mode for increased sensitivity or rate-integrating mode for greatly increased dynamic range and bandwidth, however control is challenging and the performance is sensitive to the matching of the modes. This thesis proposes a system built on open and inexpensive software-defined radio (SDR) hardware and open source software for gyroscope characterization and control. The characterization system measures ring-down of devices with damping times and automatically tunes the vibration modes from over 40 Hz mismatch to better than 100 mHz in 3 minutes. When used for rate-gyroscope operation the system provides an FPGA implementation of rate gyroscope control with amplitude, rate and quadrature closed-loop control in the SDR hardware which demonstrates 400% improvement in noise and stability over open-loop operation. The system also operates in a RIG mode with hybrid software/firmware control and demonstrates continuous operation for several hours, unlike previous systems which are limited by the gyroscope ring-down time. The hybrid mode also has a simulation module for development of advanced gyroscope control algorithms. Advanced controls proposed for RIG operation show over 1000% improvement in effective frequency and damping mismatch in simulation and 25% reduction in drift due to damping mismatch in a test RIG. By tuning the compensation, the drift can be reduced by almost 90%, with worst case drift decreased to -41 deg/s and RMS drift to -21 deg/s. Harmonic analysis of the anisotropy in a rate-integrating gyroscope measured with this control system is presented to guide development of new error models which will further improve performance.PHDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/96121/1/jagregor_1.pd

Energy efficient control of electrostatically actuated MEMS

Plenty of Micro-electro-mechanical Systems (MEMS) devices are actuated using electrostatic forces, and specially, parallel-plate actuators are extensively used, due to the simplicity of their design. Nevertheless, parallel-plate actuators have some limitations due to the nonlinearity of the generated force. The dissertation analyzes the dynamics of the lumped electrostatically actuated nonlinear system, in order to obtain insight on its characteristics, define desired performance goals and implement a controller for energy efficient robustly stable actuation of MEMS resonators. In the first part of the dissertation, the modeling of the electromechanical lumped system is developed. From a complete distributed parameters model for MEMS devices which rely on electrostatic actuation, a concentrated parameters simplification is derived to be used for analysis and control design. Based on the model, energy analysis of the pull-in instability is performed. The classic approach is revisited to extend the results to models with a nonlinear springs. Analysis of the effect of dynamics is studied as an important factor for the stability of the system. From this study, the Resonant Pull-in Condition for parallel-plate electrostatically actuated MEMS resonators is defined and experimentally validated. Given the importance of the nonlinear dynamics and its richness in behaviors, Harmonic Balance is chosen as a tool to characterize the steady-state oscillation of the resonators. This characterization leads to the understanding of the key factors for large and stable oscillation of resonators. An important conclusion is reached, Harmonic Balance predicts that any oscillation amplitude is possible for any desired frequency if the appropriate voltage is applied to the resonator. And the energy consumption is dependent on this chosen oscillation frequency. Based on Harmonic Balance results, four main goals are defined for the control strategy: Stable oscillation with large amplitudes of motion; Robust oscillation independently of MEMS imperfections; Pure sinus-like oscillation for high-grade sensing; and Low energy consumption. The second part of the dissertation deals with the controller selection, design and verification. A survey of prior work on MEMS control confirms that existing control approaches cannot provide the desired performance. Consequently, a new three-stage controller is proposed to obtain the desired oscillation with the expected stability and energy efficiency. The controller has three different control loops. The first control loop includes a Robust controller designed using on µ-synthesis, to deal with MEMS resonators uncertainties. The second control loop includes an Internal-Model-Principle Resonant controller, to generate the desired control action to obtain the desired oscillation. And the third control loop handles the energy consumption minimization through an Extremum Seeking Controller, which selects the most efficient working frequency for the desired oscillation. The proposed controller is able to automatically generate the needed control voltage, as predicted by the Harmonic Balance analysis, to operate the parallel-plate electrostatically actuated MEMS resonator at the desired oscillation. Performance verification of stability, robustness, sinus-like oscillation and energy efficiency is carried out through simulation. Finally, the needed steps for a real implementation are analyzed. Independent two-sided actuation for full-range amplitude oscillation is introduced to overcome the limitations of one-sided actuation. And a modification of standard Electromechanical Amplitude Modulation is analyzed and validated for position feedback implementation. With these improvements, a MEMS resonator with the desired specifications for testing the proposed control is designed for fabrication. Based on this design, testing procedure is discussed as future work.Molts microsistemes (MEMS) són actuats amb forces electrostàtiques, i especialment, els actuadors electrostàtics de plaques paral.leles són molt usats, degut a la simplicitat del seu disseny. Tot i això, aquests actuadors tenen limitacions degut a la no-linealitat de les forces generades. La tesi analitza el sistema mecànic no-lineal actuat electrostàticament que forma el MEMS, per tal d'entendre'n les característiques, definir objectius de control de l'oscil.lació, i implementar un controlador robust, estable i eficient energèticament. A la primera part de la tesi es desenvolupa el modelat del sistema electromecànic complert. A partir de la formulació de paràmetres distribuïts aplicada a dispositius MEMS amb actuació electrostàtica, es deriva una formulació de paràmetres concentrats per a l'anàlisi i el disseny del control. Basat en aquest model, s'analitza energèticament la inestabilitat anomenada Pull-in, ampliant els resultats de l'enfocament clàssic al model amb motlles no-lineals. Dins de l'anàlisi, l'evolució dinàmica s'estudia per ser un factor important per a l'estabilitat. D'aquest estudi, la Resonant Pull-in Condition per a actuadors electrostàtics de plaques paral.leles es defineix i es valida experimentalment. Donada la importància de la dinàmica no-lineal del sistema i la seva riquesa de comportaments, s'utilitza Balanç d'Harmònics per tal de caracteritzar les oscil.lacions en estacionari. Aquesta caracterització permet entendre els factors claus per a obtenir oscil.lacions estables i d'amplitud elevada. El Balanç d'Harmònics dóna una conclusió important: qualsevol amplitud d'oscil.lació és possible per a qualsevol freqüència desitjada si s'aplica el voltatge adequat al ressonador. I el consum energètic associat a aquesta oscil.lació depèn de la freqüència triada. Llavors, basat en aquests resultats, quatre objectius es plantegen per a l'estratègia de control: oscil.lació estable amb amplituds elevades; robustesa de l'oscil.lació independentment de les imperfeccions dels MEMS; oscil.lació sinusoïdal sense harmònics per a aplicacions d'alta precisió; i baix consum energètic. La segona part de la tesi tracta la selecció, disseny i verificació dun controlador adequat per a aquests objectius. La revisió dels treballs existents en control de MEMS confirma que cap dels enfocaments actuals permet obtenir els objectius desitjats. En conseqüència, es proposa el disseny d'un nou controlador amb tres etapes per tal d'obtenir l'oscil.lació desitjada amb estabilitat i eficiència energètica. El controlador té tres llaços de control. Al primer llaç, un controlador robust dissenyat amb µ-síntesis gestiona les incertes es dels MEMS. El segon llaç inclou un controlador Ressonant, basat en el Principi del Model Intern, per a generar l'acció de control necessària per a obtenir l'oscil.lació desitjada. I el tercer llaç de control gestiona la minimització de l'energia consumida mitjançant un controlador basat en Extremum Seeking, el qual selecciona la freqüència de treball més eficient energèticament per a l'oscil.lació triada. El controlador proposat és capaç de generar automàticament el voltatge necessari, igual al previst pel Balanç d'Harmònics, per tal d'operar electrostàticament amb plaques paral.leles els ressonadors MEMS. Mitjançant simulació se'n verifica l'estabilitat, robustesa, inexistència d'harmònics i eficiència energètica de l'oscil.lació. Finalment, la implementació real és analitzada. En primer lloc, un nou esquema d'actuació per dos costats amb voltatges independents es proposa per aconseguir l'oscil.lació del ressonador en tot el rang d'amplituds. I en segon lloc, una modificació del sensat amb Modulació d'Amplitud Electromecànica s'utilitza per tancar el llaç de control de posició. Amb aquestes millores, un ressonador MEMS es dissenya per a ser fabricat i validar el control. Basat en aquest disseny, es proposa un procediment de test plantejat com a treball futur.Postprint (published version

A Sub-Centimeter Ranging Precision LIDAR Sensor Prototype Based on ILO-TDC

This thesis introduces a high-resolution light detection and ranging (LIDAR) sensor system-on-a-chip (SoC) that performs sub-centimeter ranging precision and maximally 124-meter ranging distance. With off-chip connected avalanche photodiodes (APDs), the time-of-flight (ToF) are resolved through 31×1 time-correlated single photon counting (TCSPC) channels. Embedded time-to-digital converters (TDCs) support 52-ps time resolution and 14-bit dynamic range. A novel injection-locked oscillator (ILO) based TDC are proposed to minimize the power of fine TDC clock distribution, and improve time precision. The global PVT variation among ILO clock distribution is calibrated by an on-chip phase-looked-loop (PLL) that assures a reliable counting performance over wide operating range. The proposed LIDAR sensor is designed, fabricated, and tested in the 65nm CMOS technology. Whole SoC consumes 37mW and each TDC channel consumes 788μW at nominal operation. The proposed TDC design achieved single-shot precision of 38.5 ps, channel uniformity of 14 ps, and DNL/INL of 0.56/1.56 LSB, respectively. The performance of proposed ILO-TDC makes it an excellent candidate for global counting TCSPC in automotive LIDAR

Fabrication and characterization of microelectromechanical resonators

Cataloged from PDF version of article.Micromachined mechanical resonators are of considerable interest because of their many important scienti c and technological applications. They can be used as a components of radio-frequency lters in communication systems, mechanical electrometer or magnetometer for sensitive detection of force, charge, pressure. This work is directed towards the fabrication and characterization of microelectromechanical resonators, cantilevers and bridges. The SOI cantilever and the silicon nitride cantilevers and bridges are fabricated by using surface micromachining techniques. They are fabricated in the Advanced Research Laboratory of Bilkent University. The center frequencies are ranging from 20 kHz to 270 kHz. The characterization of cantilevers and bridges are done by using the beam de ection method and the ber optic interferometer method. The dynamic response of the rst devices, such as the resonance frequencies and the quality factors will be reported. In addition, simple beam theory and some fundamental loss mechanisms will be discussed. The experimental results will also be compared with the theoretical ones.Özer, SevilM.S

Silicon-micromachined Vibratory Diffraction Gratings for Miniaturized High-resolution Rapid Laser Scanning

Ph.DDOCTOR OF PHILOSOPH

Energy-Efficient Wireless Circuits and Systems for Internet of Things

As the demand of ultra-low power (ULP) systems for internet of thing (IoT) applications has been increasing, large efforts on evolving a new computing class is actively ongoing. The evolution of the new computing class, however, faced challenges due to hard constraints on the RF systems. Significant efforts on reducing power of power-hungry wireless radios have been done. The ULP radios, however, are mostly not standard compliant which poses a challenge to wide spread adoption. Being compliant with the WiFi network protocol can maximize an ULP radio’s potential of utilization, however, this standard demands excessive power consumption of over 10mW, that is hardly compatible with in ULP systems even with heavy duty-cycling. Also, lots of efforts to minimize off-chip components in ULP IoT device have been done, however, still not enough for practical usage without a clean external reference, therefore, this limits scaling on cost and form-factor of the new computer class of IoT applications. This research is motivated by those challenges on the RF systems, and each work focuses on radio designs for IoT applications in various aspects. First, the research covers several endeavors for relieving energy constraints on RF systems by utilizing existing network protocols that eventually meets both low-active power, and widespread adoption. This includes novel approaches on 802.11 communication with articulate iterations on low-power RF systems. The research presents three prototypes as power-efficient WiFi wake-up receivers, which bridges the gap between industry standard radios and ULP IoT radios. The proposed WiFi wake-up receivers operate with low power consumption and remain compatible with the WiFi protocol by using back-channel communication. Back-channel communication embeds a signal into a WiFi compliant transmission changing the firmware in the access point, or more specifically just the data in the payload of the WiFi packet. With a specific sequence of data in the packet, the transmitter can output a signal that mimics a modulation that is more conducive for ULP receivers, such as OOK and FSK. In this work, low power mixer-first receivers, and the first fully integrated ultra-low voltage receiver are presented, that are compatible with WiFi through back-channel communication. Another main contribution of this work is in relieving the integration challenge of IoT devices by removing the need for external, or off-chip crystals and antennas. This enables a small form-factor on the order of mm3-scale, useful for medical research and ubiquitous sensing applications. A crystal-less small form factor fully integrated 60GHz transceiver with on-chip 12-channel frequency reference, and good peak gain dual-mode on-chip antenna is presented.PHDElectrical and Computer EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/162975/1/jaeim_1.pd