RESOLUTION LIMITS FOR RESONANT MEMS SENSORS BASED ON DISCRETE RELAY FEEDBACK TECHNIQUES

Submitted on behalf of EDA Publishing Association (http://irevues.inist.fr/handle/2042/5920)International audienceThis paper is devoted to the analysis of resonant MEMS sensors based on discrete relay feedback techniques. One drawback of such techniques is that some synchronization usually occurs between the discrete part and the continuous part of the system: this results in sensor responses that are very similar to the curves known as devil's staircases, i.e. the frequency does not vary smoothly with the sensor's input. The main contribution of this paper is a theoretical calculation of the resolution of such systems. The resolutions of two existing resonant MEMS architectures are then calculated and these results are discussed

Linear analysis of the influence of FIR feedback filters on the response of the pulsed digital oscillator

The original publication is available at www.springerlink.comThe objective of this work is to extend the linear analysis of PulsedDigitalOscillators to those topologies having a Finite Impulse Response (FIR) in the feedback loop of the circuit. It will be shown with two specific examples how the overall response of the oscillator can be adjusted to some point by changing the feedback filter, when the resonator presents heavy damping losses. Extensive discrete-time simulations and experimental results obtained with a MEMS cantilever with thermoelectric actuation and piezoresistive position sensing are presented. It will be experimentally shown that the performance of the oscillator is good even below the Nyquist limit

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

RF-MEMS switches for reconfigurable antennas

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Reconfigurable antennas are attractive for many military and commercial applications where it is required to have a single antenna that can be dynamically reconfigured to transmit or receive on multiple frequency bands and patterns. RF-MEMS is a promising technology that has the potential to revolutionize RF and microwave system implementation for next generation telecommunication applications. Despite the efforts of top industrial and academic labs, commercialization of RFMEMS switches has lagged expectations. These problems are connected with switch design (high actuation voltage, low restoring force, low power handling), packaging (contamination layers) and actuation control (high impact force, wear, fatique). This Thesis focuses on the design and control of a novel ohmic RF-MEMS switch specified for reconfigurable antennas applications. This new switch design focuses on the failure mechanisms restriction, the simplicity in fabrication, the power handling and consumption, as well as controllability. Finally, significant attention has been paid in the switch’s electromagnetic characteristics. Efficient switch control implies increased reliability. Towards this target three novel control modes are presented. 1) Optimization of a tailored pulse under Taguchi’s statistical method, which produces promising results but is also sensitive to fabrication tolerances. 2) Quantification of resistive damping control mode, which produces better results only during the pull-down phase of the switch while it is possible to be implemented successfully in very stiff devices. 3) The “Hybrid” control mode, which includes both aforementioned techniques, offering outstanding switching control, as well as immunity to fabrication tolerances, allowing an ensemble of switches rendering an antenna reconfigurable, to be used. Another issue that has been addressed throughout this work is the design and optimization of a reconfigurable, in pattern and frequency, three element Yagi-Uda antenna. The optimization of the antenna’s dimensions has been accomplished through the implementation of a novel technique based on Taguchi’s method, capable of systematically searching wider areas, named as “Grid-Taguchi” method

The Boston University Photonics Center annual report 2009-2010

This repository item contains an annual report that summarizes activities of the Boston University Photonics Center for the period from July 2009 through June 2010. The report provides quantitative and descriptive information regarding photonics programs in education, interdisciplinary research, business innovation, and technology development. The Boston University Photonics Center (BUPC) is an interdisciplinary hub for education, research, scholarship, innovation, and technology development associated with practical uses of light.This report summarizes activities of the Boston University Photonics Center (BUPC) during the period July 2009 through June 2010. These activities span the Center’s complementary missions in education, research, technology development, and commercialization. In education, twenty-three BUPC graduate students received Ph.D. diplomas. BUPC faculty taught thirty-one photonics courses. Five graduate students were funded through the Photonics Fellowship Program. BUPC supported a Research Experiences for Undergraduates (REU) site in Photonics, which hosted summer interns in a ten-week program. Each REU student presented their research results to a panel of faculty and graduate students. Professors Goldberg and Swan continued their work with K-12 student outreach programs. Professor Goldberg’s Boston Urban Fellows Project started its sixth year. Professor Swan’s collaborative Four Schools for Women in Engineering program entered its third year. For more on our education programs, turn to the Education section on page 67. In research, BUPC faculty published journal papers spanning the field of photonics. Twelve patents were awarded to faculty this year for new innovations in the field. A number of awards for outstanding achievement in education and research were presented to BUPC faculty members. These honors include NSF CAREER Awards for Professors Altug, Dal Negro and Reinhard. New external grant funding for the 2009-2010 fiscal year totaled $21.1M, including$4.0M through a Cooperative Agreement with the U.S. Army Research Laboratory (ARL). For more information on our research activities, turn to the Research section on page 24. In technology development, the Department of Defense (DoD) continued to support the COBRA prototype systems. These photonics-technologies were pioneered by BUPC faculty and staff and have been deployed for field test and use at the United States Army Medical Research Institute for Infectious Diseases. New technology development projects for nuclear weapon detection, biodosimetry and terahertz imaging were launched and previously developed technologies for bacterial and viral sensing advanced toward commercial transition. For more information on our technology development pipeline and projects, turn to the Technology Development section on page 54. In commercialization, the business incubator continues to operate at capacity. Its tenants include more than a dozen technology companies with core business interests primarily in photonics and life sciences. It houses several companies founded by current and former BU faculty and students and provides students with an opportunity to assist, observe, and learn from start-up companies. For more information about business incubator activities, turn to the Business Incubation chapter in the Facilities and Equipment section on page 84. In early 2010, the BUPC unveiled a five-year strategic plan as part of the University’s comprehensive review of centers and institutes. The BUPC strategic plan will enhance the Center’s position as an international leader in photonics research. For more information about the strategic plan, turn to the BUPC Strategic Plan section on page 8

Development and characterisation of traceable force measurement for nanotechnology

Traceable low force metrology should be an essential tool for nanotechnology. Traceable measurement of micro- and nanonewton forces would allow independent measurement and comparison on material properties, MEMS behaviour and nanodimensional measurement uncertainties. Yet the current traceability infrastructure in the UK is incomplete. This thesis describes the incremental development of the low force facility at the National Physical Laboratory (NPL). The novel contribution of this thesis has three components. First, specific modifications to the NPL Low Force Balance were undertaken. This involved developing novel or highly modified solutions to address key issues, as well as undertaking detailed comparions with external ans internal traceability references. Second, a triskelion force sensor flexure was proposed and mathematically modelled using both analytical and finite element techniques, and compared to experimentally measured spring constant estimates. The models compared satisfactorily, though fabrication defects in developed prototype artefacts limited the experimental confirmation of the models. Third, a piezoelectric sensor approach for quasistatic force measurement was proposed, experimentally evaluated and rejected. Finally, an improved design for a low force transfer artefact system is presented, harnessing the findings of the reported investigations. The proposed design combines proven strain-sensing technology with the advantageous triskelion flexure, incorporating an external stage and packaging aspects to achieve the requirements for a traceable low force transfer artefact

Doctor of Philosophy

dissertationThe terahertz frequency band extends from deep infrared (100 THz) down to millimeter waves (0.4 THz), and this band was mostly inaccessible due to the lack of appropriate sources and detectors. Those with access to this band had to endure the small-intensity pulsed signals (nanowatts to microwatts) that the terahertz sources of those times could provide. In recent years, however, sufficient development has led to the availability of terahertz sources with sufficient power (1-100 μW) and the ease of use these sources has in turn enabled researchers to develop newer sources, detectors, and application areas. The terahertz regime is interesting because a) many molecules have vibrational, rotation and transition absorption bands in this regime, b) the terahertz electromagnetic wavelength is sufficiently small to resolve centimeter to millimeter scale objects, and c) scattering and absorption in metals in the terahertz regime make it very challenging to devise terahertz signal processing circuits. Thus, performing terahertz reflection/transmission measurements may enable precise identification of chemicals in a sample. Furthermore, small wavelengths and strong scattering by metallic objects make imaging with terahertz waves quite attractive. Finally, the ability to devise terahertz communication circuits and links will provide access to a frequency domain that is restricted and not available to others. One of the main objectives of this work is to develop 0.75 - 1.1 terahertz (free space wavelength 272 μm â€" 400 μm) amplifiers. Another objective of this work is to explore the suitability of terahertz waves in biological imaging and sensing. The terahertz amplifiers developed in this work consisted of distributed components such as rectangular waveguides and cylindrical dielectric resonators. In contrast to discrete amplifiers, which are based on solid-state devices, distributed traveling wave amplifiers can potentially handle and produce larger powers. Three different distributed terahertz amplifier circuits were considered in this work. These were based on a) coupled dielectric resonators, b) dielectric waveguides with periodic slots, and c) metallic meandering waveguides. The result of the hot test of the last circuit on interaction with an electron beam energy source yielded an amplification of 12 dB of a -55 dBm, 0.9 terahertz signal over ~1 gigahertz bandwidth. The electron beam acceleration voltage was 4.8 kV and its current was approximately 20 microamps. The terahertz biosensing system developed in this work was used to study the unique interaction of terahertz waves with the chemical and physical components of biological tissues, and the products of biochemical reactions. A terahertz near-field imaging system was also developed to image mouse brain slices, plants, and bug wings. In addition, this work also demonstrated the capabilities and limitations of terahertz waves for the real-time noninvasive monitoring of bioethanol production by yeast cells

MEMS Actuation and Self-Assembly Applied to RF and Optical Devices

The focus of this work involves optical and RF (radio frequency) applications of novel microactuation and self-assembly techniques in MEMS (Microelectromechanical systems). The scaling of physical forces into the micro domain is favorably used to design several types of actuators that can provide large forces and large static displacements at low operation voltages. A self-assembly method based on thermally induced localized plastic deformation of microstructures has been developed to obtain truly three-dimensional structures from a planar fabrication process. RF applications include variable discrete components such as capacitors and inductors as well as tunable coupling circuits. Optical applications include scanning micromirrors with large scan angles (>90 degrees), low operation voltages (<10 Volts), and multiple degrees of freedom. One and two-dimensional periodic structures with variable periods and orientations (with respect to an incident wave) are investigated as well, and analyzed using optical phased array concepts. Throughout the research, permanent tuning via plastic deformation and power-off latching techniques are used in order to demonstrate that the optical and RF devices can exhibit zero quiescent power consumption once their geometry is set