1,720,965 research outputs found
Ultra-Low Power Circuits for Batteryless Energy Harvesting Systems and Thermal Compensation in Resistive In-Memory Computing
No full textEmbedded systems, from wearable health monitors and implantable diagnostics to environmental sensor nodes, are becoming increasingly prevalent in modern life. These platforms are often expected to operate continuously under severe energy constraints, where frequent battery replacement is impractical. To address this, there is a growing need for ultra-low-power (ULP) circuits capable of harvesting ambient energy from sources such as radio frequency (RF) fields, biochemical reactions, and photovoltaic cells. Ensuring stable operation under these limited and varying energy conditions requires circuits with ULP consumption and robust performance under variations. This thesis presents an approach to the design, implementation, and experimental validation of ULP integrated circuits across multiple circuit blocks, tailored for energy-autonomous and flexible systems. The contributions span several key building blocks of energy-harvesting systems, including variation-insensitive voltage and current reference generators, RF-DC converters, low-dropout (LDO) regulators, and switched-capacitor (SC) DC-DC converters with finegrained, arithmetic progression-based voltage scaling. Further, the work introduces thermal compensation techniques to maintain computational accuracy for analog in-memory computing units under varying thermal conditions. The circuits presented in this thesis are designed and fabricated using a conventional CMOS in 65 nm and Pragmatic 600 nm flexible indium gallium zinc oxide (IGZO) based technology using unipolar TFT-based transistors.
Variation-insensitive reference generators form the foundation for reliable biasing across the circuits presented in this work. To address this, the thesis implements amplifier-free, MOS-based voltage and current references that ensure stable operation under varying conditions. A dual-mode, all-NMOS circuit is developed to function both as a voltage reference and a temperature sensor, enabling efficient circuit reuse in energy and area constrained systems. This circuit is further extended to flexible electronics, with a voltage reference designed using IGZO thin-film transistors. For energy regulation, an LDO based on IGZO unipolar transistors is presented, offering efficient voltage regulation under a low quiescent current of 150 nA. An RF-to-DC converter targeting operation in 13.56 MHz is also developed to harvest energy from wireless sources. To support energy sources with variable and degrading outputs, such as biofuel or zinc-air cells, a reconfigurable switched-capacitor DC-DC converter is introduced, with arithmetic progression control of voltage conversion steps of 0.125.
The proposed circuits are implemented for voided fluid volume sensing in smart diapers powered by urine-based energy harvesters. Additionally, voltage regulation using DC-DC converters operating from degrading and decaying energy sources has been designed. The circuits implemented are validated through system-level integration in practical applications. A smart diaper platform powered entirely by harvested urine energy demonstrates the feasibility of fully autonomous operation. Additionally, the thesis addresses thermal variability in analog in-memory computing arrays through two compensation techniques: one using programmable calibration, and another using on-chip thermal sensing for automatic adjustment. The circuits developed in this work enable energy-autonomous operation in batteryless systems and provide robust thermal stability for analog in-memory computing.navigointi mahdollistakuvilla vaihtoehtoiset kuvauksettaulukot saavutettaviastrukturell navigationalternativa textuella beskrivningar för bildertabeller tillgängligastructural navigationalternative textual descriptions for imagestables accessibl
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
A Compact Untrimmed 48ppm/°C All MOS Current Reference Circuit
No full textFunding Information: The authors are grateful to Academy of Finland for funding this work under the project EHIR (Wireless impulse radio data link powered by energy harvesting). Publisher Copyright: © 2022 IEEE.An ultra-low power and low-cost (area efficient) nano-Ampere current reference circuit designed in a 65 nm technology is presented in this paper: The proposed circuit is a resistorless beta multiplier current reference circuit that uses self cascode composite MOSFETs in triode region. Circuit analysis has been discussed in the paper. The simulated circuit consumes power of 550 nW at a nominal operating voltage of 1.33 V and occupies area of 0.0031 mm2. The design provides a line regulation of 1.9 %/V over an operating voltage range of 1.25 V to 1.4 V. Temperature coefficient (TC) of the circuit at nominal voltage of 1.33 V is 48 ppm/°C for a wide temperature range of-40°C to 85°C. Output current of the circuit at nominal voltage is 104.2 nA with a small process variation of only 4 %.Peer reviewe
A Sub-nW Temperature Invariant Voltage Reference in a Unipolar TFT-based Flexible IC Technology
No full textPublisher Copyright: © 2024 IEEE.Voltage reference circuits are crucial for any mixed-signal circuits, providing PVT (Process, Voltage, Temperature) robust output for the system's stability and accuracy. This paper presents a novel voltage reference circuit implemented in an indium gallium zinc oxide (IGZO) based thin film transistors (TFT) technology, proposing for the first time a sub-nanowatt, area-efficient circuit realized with only a single N-type TFT in a 600 nm technology. The design occupies a minimal area of 27x37 μm2, operates across a broad supply voltage range from 0.5 V to 3 V, and maintains functionality from 0 °C to 100 °C. The circuit has an ultra-low power consumption between 0.75 nW to 1.2 nW while achieving an output voltage of 454 mV with a temperature coefficient (TC) as low as 28.9 ppm/°C. The simulated results, which include process variation, temperature dependence, line sensitivity and power supply rejection ratio measurements, underline the circuit's potential for high-efficiency, low-power applications in next-generation flexible electronics.Peer reviewe
Flexible RF to DC Converter for Wireless Power Transfer in NFC and Biomedical Systems
No full textPublisher Copyright: © 2024 IEEE.To facilitate the versatile use of flexible energy harvesters, this work discusses the design and characterization of a novel radio frequency (RF) to DC converter built in indium gallium zinc oxide (IGZO) thin film transistor (TFT) technology, developed to meet the energy requirements of near-field communication (NFC) and biomedical applications. The design uses a hybrid topology that combines the efficiency of a cross-coupled converter with the voltage-enhancing capabilities of Dickson charge pumps. This converter is designed to address the challenges of variable RF environments because of its dynamic adjustment technique involving self-biasing resistors and gate voltage-boosting capacitors. The circuit is implemented in a 600 nm TFT technology, and post-layout simulations verify that the circuit can achieve a peak power conversion efficiency (PCE) of 41.5 % at a load resistance of 906 kΩ and exhibiting sensitivity levels as low as -20 dBm. The compact area of 0.0127 mm2 gives this circuit the potential for integration into disposable NFC tags and single-use biomedical devices where efficiency, size, and cost are key factors.Peer reviewe
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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