1,720,962 research outputs found
An Element-Level Sigma-Delta ADC for Ultrasound Imaging
No full textThis work presents an architecture capable of digitizing every channel of an ultrasound transducer array independently and simultaneously. This feature is achieved by exploiting the frequency response of the piezoelectric transducer in order to save area and reduce to a minimum the required building blocks of the ADC. The transducer is used as an electro-mechanical resonator, which is embedded in a band-pass continuous-time, multi-bit ΣΔ modulator. This converter relies entirely on the noise shaping provided by the transducer, which proves to be sufficient to reach the required specifications. Each converter only includes an inverter-based transimpedance amplifier, a variable gain amplifier for time-gain compensation and a 3-bit tracking quantizer, which comprises two comparators and two DACs. A prototype chip has been fabricated in TSMC 0.18 technology, featuring 20 channels, with one ADC per channel, and 20 parallel high-speed LVDS transmitters to convey the bitstreams out to the measurement system. The whole modulator, clocked at 200, achieves an area of 150 × 150, a power consumption of 800 and an SNR of 47dB in a 75% bandwidth around a transmit frequency of 5. The measurements clearly show the desired noise shaping behaviour, thus proving that the proposed concept is valid.Electrical Engineering, Mathematics and Computer ScienceElectronic Instrumentatio
Design of an Energy-Efficient Interface Circuit for a MEMS-based Capacitive Pressure Sensor
No full textThis thesis presents an incremental ?? capacitance-to-digital converter (CDC) that serves as an interface circuit for a MEMS-based pressure sensor. The thesis presents a systematic analysis of the CDC and compares different CDC architectures. A novel non-linear CDC is also proposed and analysed. Energy-efficiency of the CDC is improved by implementation of various design techniques like double sampling, system-level chopping and a novel inverter-based OTA. The CDC has been designed in such a way that it can operate with either an on-chip or external pressure sensor. The CDC can be tuned to compensate for a wide range of baseline capacitance. The CDC operates over a pressure range of 0-1.3 bar and achieves a pressure resolution of 1e?5 bar (equivalent to a resolution of 16 bits). The CDC is implemented in NXP 0.16?m 1P6M technology. The circuit design and layout of the CDC are presented. The CDC consumes 2.33?A from a 1.2V supply resulting in an energy consumption of only 2.01nJ, a significant improvement over the state-of-the-art.Microelectronics & Computer EngineeringElectrical Engineering, Mathematics and Computer Scienc
Een draadloze sensor voor het monitoren van bederfelijke producten
No full textOm een pH-sensor[1], ontwikkeld binnen het PASTEUR-project [2], aan te kunnen sturen en uit te kunnen lezen is een ontwerp voor een sensorsysteem gemaakt dat de pH en temperatuur in vlees kan monitoren. Belangrijke eigenschappen hiervan zijn het lage energieverbruik, de draadloze digitale communicatie en het kleine formaat. Het systeem meet gedurende 48 uur elke tien minuten de pH en slaat deze op. Andere intervallen zijn ook mogelijk, maar dat verandert wel de tijd waarin het systeem blijft werken. De gebruiker kan al deze data ophalen via een reader en ook een instantane meting aanvragen. Het sensorsysteem is opgedeeld in twee onderdelen: de draadloze communicatie en de sensor node. In deze thesis wordt het ontwerp van de sensor node besproken. Deze stuurt de sensor daadwerkelijk aan, slaat de rauwe data van de pH en temperatuur op en geeft dit door aan de draadloze communicatie zodat deze de data kan versturen naar een computer, die de data verder verwerkt. De sensor node bestaat uit een microcontroller en een extern geheugen om alle data in op te slaan. Daarnaast bestaat het uit hardware om de communicatie met de RFID-tag en de sensorstick mogelijk te maken. Het systeem bevindt zich het grootste gedeelte van de tijd in sleep mode om energie te besparen. De microcontroller die hiervoor gebruikt is, is de C8051F986 van Silicon Labs, welke de laagste sleep mode current heeft op de huidige markt. Het geheugen is een 24AA64-I/OT, een EEPROM chip van 64kbit met I2C communicatie. De draadloze communicatie zal door middel van RFIDtechniek tot stand komen. De groep die dat ontworpen heeft, gebruikt de TMS37157, een passieve RFID interface met SPI aansturing. Een protocol is ontwikkeld, genaamd het Data Link Protocol, om foutloze dataoverdracht te garanderen. De sensor node wordt gevoed door een 3V lithium knoopcel. De microcontroller en het geheugen wordt direct gevoed door de batterijspanning, de pH-sensor door een 1,8V regulator, en het RFID subsysteem wordt enkel gevoed door de RF energie van de reader. De software is geschreven in C en werkt zonder operating system, omdat er slechts één proces tegelijkertijd zal worden uitgevoerd en een OS dus niet noodzakelijk is. De software is opgebouwd uit een toplaag, een middenlaag en drivers. De toplaag bestaat uit de mainfunctie die controle heeft over de functie die met de TMS37157-chip communiceert, de functie die het geheugen beheert, de slaapfunctie en de functie die de pH-sensor aanstuurt en uitleest. Vanuit de TMS37157-chip kunnen acht verschillende commando’s komen die door de sensor node moeten worden opgevolgd. Op basis hiervan roept de mainfunctie de juiste functies aan. Ondanks de CRC-check van de TMS37157-chip moet de foutdetectie van de draadloze communicatie extra verzekerd worden, omdat de CRC geen rekening kan houden met geheel niet ontvangen van verzendingen. Daarvoor is er een data link protocol ontwikkeld. In het geheugen worden de kalibratiemetingen, de geplande metingen en de instantane metingen apart opgeslagen. Hierbij is ervoor gezorgd dat genoeg ruimte is om acht kalibratiemetingen op te slaan. Bij deze kalibratiemetingen worden de time stamp en de pH-waarde, door de gebruiker meegegeven, opgeslagen. Zonder getriggerde metingen is er daarnaast nog ruimte om 2698 geplande metingen op te slaan, wat meer dan voldoende is voor wat nodig is om 48 uur lang elke tien minuten een meting te doen. Dit aantal is wat minder met getriggerde metingen erbij, omdat deze meer ruimte innemen. Het ontwerp is nog niet getest, dus er zijn nog geen algemene resultaten te zien, maar met behulp van een logic analyser is wel aangetoond dat het beheren van de EEPROM en de communicatie met de TMS-chip via SPI werkt.Microelectronics & Computer EngineeringElectrical Engineering, Mathematics and Computer Scienc
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Ping-Pong-Pang Instrumentation Amplifier
No full textThis thesis describes the implementation of a Precision Instrumentation Amplifier using a Current Feedback Instrumentation Amplifier topology (CFIA). CFIAs are attractive for sensor readout, because of their high CMRR and their ability to interface with ground-referenced sensors. Several chopping and auto-zeroing techniques have been developed to reduce the offset and 1/f noise of such amplifiers to the ?V level. As a result, their dominant source of error is now gain error, which is limited by mismatch to at best 0.1%. This paper describes a CFIA that applies dynamic element matching (DEM) to achieve a gain error of less than 0.04%. Moreover, it presents the first silicon implementation of the ping-pong-pang (PPP) auto-zeroing scheme, which enables a 3.5× reduction in power consumption and 2.5× improvement in gain error as compared to state-of-the-art ping-pong auto-zeroed CFIAs.Electronic InstrumentationMicroelectronics & Computer EngineeringElectrical Engineering, Mathematics and Computer Scienc
Energy-efficient capacitive-sensor interface based on an incremental Delta-Sigma modulator employing current-starved inverter-based OTAs
No full textAn interface circuit for a fully-integrated capacitive humidity-sensor is implemented using 0.16?m standard CMOS technology. This interface circuit is intended to be used in a smart RFID sensor platform. This thesis focuses on improving the energy-efficiency of the interface circuit. A third-order incremental delta-sigma converter based on switched-capacitor integrators is presented. Due to the fact that the operational trans-conductance amplifier (OTA), as a major building block for an integrator, consumes most of the power in the whole interface circuit, this work mainly concentrates on improving the energy-efficiency of the OTAs in the three integrators. A fully-differential current-starved inverter-based OTA structure is proposed for the integrator. A dynamic power-down scenario is applied to reduce the power consumption by approximately 20%. Detailed analysis and design optimizations are also provided. The interface achieves 13-bit capacitance-to-digital conversion while consuming 6.8?W from a 1.2V supply, resulting in a figure-of-merit (F.o.M) around 0.17pJ/Step. The circuit design and layout of a test chip are presented. Simulation results confirm the expected improvement in energy-efficiency.Electronic Instrumentation LabElectrical Engineering-MicroelectronicsElectrical Engineering, Mathematics and Computer Scienc
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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