563 research outputs found

    High-Power Gallium Nitride HIFU Transmitter with Integrated Real-Time Current and Voltage Measurement

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    High-Intensity Focused Ultrasound (HIFU) therapy provides a non-invasive technique with which to destroy cancerous tissue without using ionizing radiation. To drive large single-element HIFU transducers, ultrasound transmitters capable of delivering high powers at relevant frequencies are required. The acoustic power delivered to a transducers focal region will determine the treated area, and due to safety concerns and intervening layers of attenuation, control of this output power is critical. A typical setup involves large inefficient linear power amplifiers to drive the transducer. Switched mode transmitters allow for a more compact drive system with higher efficiencies, with multi-level transmitters allowing control over the output power. Real-time monitoring of power delivered can avoid damage to the transducer and injury to patients due to over treatment, and allow for precise control over the output power. This study demonstrates a transformer-less, high power switched mode transmit transmitter based on Gallium-Nitride (GaN) transistors that is capable of delivering peak powers up to 1.8 kW at up to 600 Vpp, while operating at frequencies from DC to 5 MHz. The design includes a 12 bit 16 MHz floating Current/Voltage (I-V) measurement circuit to allow real-time high-side monitoring of the power delivered to the transducer allowing use with multi-element transducers

    A multi-mode sonar transmitter

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    This project was initiated to evaluate appropriate microprocessor and digital logic techniques that could increase the flexibility and effectiveness of a sonar transmitter. The study led to a multi-channel signal synthesis concept designed to exploit 'phased array' steering techniques. Two versions of the equipment have now been built and evaluated. Mk.I is a relatively low power 15 channel system with 2 kilowatts total electrical power using a 40 kHz 15 λ x 1 line array. This system proved the practicability of the basic concept and its success led to the 16 kilowatt Mk2 high power version which drives a 16λ x 16 λ wideband transducer array. The study included: The design and construction of a multi-channel signal generator. The writing of control and signal synthesis software. The design, evaluation and commissioning of suitable linear power amplifiers . Investigations into suitable transducers and phased array design, leading to the manufacture of suitable matched wide band multi-channel 'staved' transducer arrays. Finally, a series of trials were made in a variety of open water conditions to evaluate the systems performance and investigate the multiple modes of operation that have been developed. The system has successfully demonstrated that transmitter beam steering is both practical and flexible. The techniques implemented permit sector interrogation by 'within-pulse' type sweeps, by 'Ripple-fire' and by transmitting steered 'Pings' sequentially on prededermined bearings. Each mode allows considerable flexibility in the generated waveform shape and frequency. The 'Multi-Mode' capability of this approach was conceived primarily as a research tool but many of the modes can be isolated and exploited in dedicated applications

    An ultrasonic system for intravascular measurement and visualisation of anatomical structures and blood flow

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    Imperial Users onl

    Development of electronics for microultrasound capsule endoscopy

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    Development of intracorporeal devices has surged in the last decade due to advancements in the semiconductor industry, energy storage and low-power sensing systems. This work aims to present a thorough systematic overview and exploration of the microultrasound (µUS) capsule endoscopy (CE) field as the development of electronic components will be key to a successful applicable µUSCE device. The research focused on investigating and designing high-voltage (HV, < 36 V) generating and driving circuits as well as a low-noise amplifier (LNA) for battery-powered and volume-limited systems. In implantable applications, HV generation with maximum efficiency is required to improve the operational lifetime whilst reducing the cost of the device. A fully integrated hybrid (H) charge pump (CP) comprising a serial-parallel (SP) stage was designed and manufactured for > 20 V and 0 - 100 µA output capabilities. The results were compared to a Dickson (DKCP) occupying the same chip area; further improvements in the SPCP topology were explored and a new switching scheme for SPCPs was introduced. A second regulated CP version was excogitated and manufactured to use with an integrated µUS pulse generator. The CP was manufactured and tested at different output currents and capacitive loads; its operation with an US pulser was evaluated and a novel self-oscillating CP mechanism to eliminate the need of an auxiliary clock generator with a minimum area overhead was devised. A single-output universal US pulser was designed, manufactured and tested with 1.5 MHz, 3 MHz, and 28 MHz arrays to achieve a means of fully-integrated, low-power transducer driving. The circuit was evaluated for power consumption and pulse generation capabilities with different loads. Pulse-echo measurements were carried out and compared with those from a commercial US research system to characterise and understand the quality of the generated pulse. A second pulser version for a 28 MHz array was derived to allow control of individual elements. The work involved its optimisation methodology and design of a novel HV feedback-based level-shifter. A low-noise amplifier (LNA) was designed for a wide bandwidth µUS array with a centre frequency of 28 MHz. The LNA was based on an energy-efficient inverter architecture. The circuit encompassed a full power-down functionality and was investigated for a self-biased operation to achieve lower chip area. The explored concepts enable realisation of low power and high performance LNAs for µUS frequencies

    Ultrasound Stimulation of a Piezoelectric Composite with Compliant Layers on Power Output for Bone Healing in Spinal Fusion Applications

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    Spinal fusion devices have up to 50% failure rates for patients who smoke or are diabetic 1. Bone healing has been accomplished through direct current (DC) electrical stimulation to improve bone healing rates 2. Current DC electrical stimulation can accomplish bone healing, but batteries are used as a source of power. Replacing a battery after fusion would require a second surgery. Many microgenerators use piezoelectric material to convert mechanical energy into electrical potential 3. In a pilot ovine study, composite spinal interbody implants made with stacked layers of piezoelectric fibers provided DC electrical stimulation at the fusion site and substantially enhanced fusion under normal loading after six weeks as compared to a control 2,4,5. To improve manufacturability while maintaining material toughness of the interbody implants, alternative manufacturing methods were explored in which compliant layers of epoxy (EPO-TEK® 301, Billerica, MA) were inserted between stacked discs of piezoelectric material, PZT-SM111 (STEMiNC-0.4mm thickness, 10mm diameter, Part No. SMD10T04F5000S111, Doral, FL). For patients with limited weight bearing abilities that cannot provide enough mechanical energy from human body movement, another method of mechanically stimulating the PZT discs would be beneficial. Many methods of wirelessly powering medical devices have been investigated including electromagnetic waves, thermoelectric devices, and ultrasound 3. Transmitted ultrasound waves can be used to mechanically activate a medical device implanted into human tissue with PZT elements 3. Using ultrasound as the loading source, the effect of varying compliant layer thicknesses on generated electrical potential and power output of the PZT compliant layer adaptive composite stacks (CLACS) in different media (water, tissue, and tissue plus bone), media thicknesses (20mm and 40mm), and loading orientations of the PZT composites with respect to the ultrasound wave front (perpendicular and parallel) were investigated. An Acuson 128xp ultrasound medical imaging machine (Mountain View, CA) was used to mechanically stimulate the PZT elements in the compliant layer thickness composites and voltage measurements were made with a Tektronix (Beaverton, OR) DPO 3034 Digital Phosphor Oscilloscope (300 MHz). The PZT composite was manufactured with six through thickness pre-poled PZT-SM511 discs (STEMiNC-0.4mm thickness, 10mm diameter, Part No. SMD10T04F5000S111, Doral, FL) that were connected electrically in parallel (EPO-TEK® H20E, Billerica, MA) with copper strips, varying compliant layer thickness (0, 0.2, 0.4, and 0.8 mm ± 0.02 mm) of medical grade epoxy slices (EPO-TEK® 301, Billerica, MA) interposed between the PZT discs, and encapsulated in medical grade epoxy (EPO-TEK® 301, Billerica, MA). After assembly, the CLACS were tested at each combination of media type, media thickness, and loading orientations. The CLACS were subject to 4MHz ultrasound waves (1 W) in a Gaussian shape pattern with a V4 vector 128 PZT element array probe (Mountain View, CA). Voltage measurements before rectification (alternating current - AC) and after rectification (direct current - DC) were recorded. Power was computed after rectification by applying an average voltage measured across the lumped internal Oscilloscope channel impedance (1 MΩ) with the influence of a variable load resistance (Ω) and capacitor (c) connected in parallel and then using P=V^2/R by combining Joule’s and Ohm’s law. By adding a compliant layer thickness in between the PZT discs of the CLACS, generated electrical potential and power output increased. As the compliant layer thickness increased there were significant increases in power output due to more deformation that occurred along the entire face and edges of the PZT discs. As media thickness increased, DC power output decreased. The CLACS produced the most power with water as the media. Significantly less power was produced in tissue media, and even less in the tissue plus bone medium (p<0.05 BoxCox Transformation). When the stacked PZT layers were being loaded perpendicular to the wave front of the ultrasound waves, there was significantly more power output than when the stacked PZT layers were being loaded parallel to the ultrasound wave front (p<0.05 BoxCox Transformation). Future work could build off this foundational study to further characterize the CLACS power output behavior. These future studies would include focused vs. unfocused ultrasound loading sources to increase the amount of mechanical energy that influences the CLACS, differing operating frequencies to match and mismatch the resonant frequency of the PZT discs and to determine optimum frequencies for certain media depths, testing more varied loading orientations, differing ultrasound intensity levels, using a combination of radially and through-thickness poled PZT discs, designing circuit components to improve electrical energy transfer (impedance matching) efficiency and implementing pulsed DC circuit logic after rectification to approach a more realistic application of DC electrical stimulation in bone healing for spinal fusion

    Digital flight control actuation system study

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    Flight control actuators and feedback sensors suitable for use in a redundant digital flight control system were examined. The most appropriate design approach for an advanced digital flight control actuation system for development and use in a fly-by-wire system was selected. The concept which was selected consisted of a PM torque motor direct drive. The selected system is compatible with concurrent and independent development efforts on the computer system and the control law mechanizations

    Precision at Scale: System Design from Tiny Biosensors to Giant Arrays

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    In order to change the world, technological advancements must be made affordable and available for the general public to use. In other words, we must be able to scale our inventions effectively. Silicon integrated circuits are crucial components in scaling electronic systems because they are mass producible and offer a phenomenal cost-to-complexity ratio. This thesis summarizes the author’s work on highly scalable sensor and array systems. It presents three high precision systems, that demonstrate how the use of highly functional radio-frequency integrated circuits enables the realization of previously unfeasible architectures

    Introduction to modern instrumentation: for hydraulics and environmental sciences

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    Preface Natural hazards and anthropic activities threaten the quality of the environment surrounding the human being, risking life and health. Among the different actions that must be taken to control the quality of the environment, the gathering of field data is a basic one. In order to obtain the needed data for environmental research, a great variety of new instruments based on electronics is used by professionals and researchers. Sometimes, the potentials and limitations of this new instrumentation remain somewhat unknown to the possible users. In order to better utilize modern instruments it is very important to understand how they work, avoiding misinterpretation of results. All instrument operators must gain proper insight into the working principles of their tools, because this internal view permits them to judge whether the instrument is appropriately selected and adequately functioning. Frequently, manufacturers have a tendency to show the great performances of their products without advising their customers that some characteristics are mutually exclusive. Car manufacturers usually show the maximum velocity that a model can reach and also the minimum fuel consumption. It is obvious for the buyer that both performances are mutually exclusive, but it is not so clear for buyers of measuring instruments. This book attempts to make clear some performances that are not easy to understand to those uninitiated in the utilization of electronic instruments. Technological changes that have occurred in the last few decades are not yet reflected in academic literature and courses; this material is the result of a course prepared with the purpose of reducing this shortage. The content of this book is intended for students of hydrology, hydraulics, oceanography, meteorology and environmental sciences. Most of the new instruments presented in the book are based on electronics, special physics principles and signal processing; therefore, basic concepts on these subjects are introduced in the first chapters (Chapters 1 to 3) with the hope that they serve as a complete, yet easy-to-digest beginning. Because of this review of concepts it is not necessary that the reader have previous information on electronics, electricity or particular physical principles to understand the topics developed later. Those readers with a solid understanding of these subjects could skip these chapters; however they are included because some students could find them as a useful synthesis. Chapter 4 is completely dedicated to the description of transducers and sensors frequently used in environmental sciences. It is described how electrical devices are modified by external parameters in order to become sensors. Also an introduction to oscillators is presented because they are used in most instruments. In the next chapters all the information presented here is recurrently referred to as needed to explain operating principles of instruments. Unauthenticated Download Date | 10/12/14 9:29 PM VIII Preface Chapters 1 to 4 are bitter pills that could discourage readers interested in the description of specific instruments. Perhaps, those readers trying this book from the beginning could abandon it before arriving at the most interesting chapters. Therefore, they could read directly Chapters 5 to 11, going back as they feel that they need the knowledge of the previous chapters. We intended to make clear all the references to the previous subjects needed to understand each one of the issues developed in the later chapters. Chapter 5 contributes to the understanding of modern instrumentation to measure flow in industrial and field conditions. Traditional mechanical meters are avoided to focus the attention on electronic ones, such as vortex, electromagnetic, acoustic, thermal, and Coriolis flowmeters. Special attention is dedicated to acoustic Doppler current profilers and acoustic Doppler velocimeters. Chapter 6 deals with two great subjects; the first is devoted to instruments for measuring dynamic and quasi static levels in liquids, mainly water. Methods to measure waves at sea and in the laboratory are explained, as well as instruments to measure slow changes such as tides or piezometric heads for hydrologic applications. The second subject includes groundwater measurement methods with emphasis on very low velocity flowmeters which measure velocity from inside a single borehole. Most of them are relatively new methods and some are based on operating principles described in the previous chapter. Seepage meters used to measure submarine groundwater discharge are also presented. Chapter 7 presents methods and instruments for measuring rain, wind and solar radiation. Even though the attention is centered on new methods, some traditional methods are described not only because they are still in use, and it is not yet clear if the new technologies will definitely replace them, but also because describing them permits their limitations and drawbacks to be better understood. Methods to measure solar radiation are described from radiation detectors to complete instruments for total radiation and radiation spectrum measurements. Chapter 8 is a long chapter where we have tried to include most remote measuring systems useful for environmental studies. It begins with a technique called DTS (Distributed Temperature Sensing) that has the particularity of being remote, but where the electromagnetic wave propagates inside a fibre optic. The chapter follows with atmosphere wind profilers using acoustic and electromagnetic waves. Radio acoustic sounding systems used to get atmospheric temperature profiles are explained in detail as well as weather radar. Methods for ocean surface currents monitoring are also introduced. The chapter ends with ground penetrating radars. Chapter 9 is an introduction to digital transmission and storage of information. This subject has been reduced to applications where information collected by field instruments has to be conveyed to a central station where it is processed and stored. Some insight into networks of instruments is developed; we think this information will help readers to select which method to use to transport information from field to office, by means of such diverse communication media as fibre optic, digital telephony, Unauthenticated Download Date | 10/12/14 9:29 PM Preface IX GSM (Global System for Mobile communications), satellite communications and private radio frequency links. Chapter 10 is devoted to satellite-based remote sensing. Introductory concepts such as image resolution and instrument?s scanning geometry are developed before describing how passive instruments estimate some meteorological parameters. Active instruments are presented in general, but the on-board data processing is emphasized due to its importance in the quality of the measurements. Hence, concepts like Synthetic Aperture Radar (SAR) and Chirp Radar are developed in detail. Scatterometers, altimeters and Lidar are described as applications of the on-board instruments to environmental sciences. Chapter 11 attempts to transfer some experiences in field measuring to the readers. A pair of case studies is included to encourage students to perform tests on the instruments before using them. In this chapter we try to condense our ideas, most of them already expressed throughout the book, about the attitude a researcher should have with modern instruments before and after a measuring field work. As can be inferred from the foregoing description the book aims to provide students with the necessary tools to adequately select and use instruments for environmental monitoring. Several examples are introduced to advise future professionals and researchers on how to measure properly, so as to make sure that the data recorded by the instruments actually represents the parameters they intend to know. With this purpose, instruments are explained in detail so that their measuring limitations are recognized. Within the entire work it is underlined how spatial and temporal scales, inherent to the instruments, condition the collection of data. Informal language and qualitative explanations are used, but enough mathematical fundamentals are given to allow the reader to reach a good quantitative knowledge. It is clear from the title of the book that it is a basic tool to introduce students to modern instrumentation; it is not intended for formed researchers with specific interests. However, general ideas on some measuring methods and on data acquisition concepts could be useful to them before buying an instrument or selecting a measuring method. Those readers interested in applying some particular method or instrument described in this book should consider these explanations just as an introduction to the subject; they will need to dig deeper in the specific bibliography before putting hands on.Fil: Guaraglia, Dardo Oscar. Universidad Nacional de la Plata. Facultad de IngenierĂ­a. Departamento de Hidraulica. Area Hidraulica Basica; Argentina. Consejo Nacional de Investigaciones CientĂ­ficas y TĂ©cnicas. Centro CientĂ­fico TecnolĂłgico Conicet - La Plata; ArgentinaFil: Pousa, Jorge Lorenzo. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Laboratorio de OceanografĂ­a Costera y Estuarios; Argentina. Consejo Nacional de Investigaciones CientĂ­ficas y TĂ©cnicas. Centro CientĂ­fico TecnolĂłgico Conicet - La Plata; Argentin
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