Gray-code TDC with improved linearity and scalability for LiDAR applications

This paper presents a TDC architecture based on a gray code oscillator with improved linearity, for FPGA implementations. The proposed architecture introduces manual routing as a method to improve the TDC linearity and precision, by controlling the gray code oscillator Datapath, which also reduces the need for calibration mechanisms. Furthermore, the proposed manual routing procedure improves the performance homogeneity across multiple TDC channels, enabling the use of the same calibration module across multiple channels, if further improved precision is required. The proposed TDC channel uses only 16 FPGA logic resources (considering the Xilinx 7 series platform), making it suitable for applications where a large number of measurement channels are required. To validate the proposed architecture and routing procedure, two channels were integrated with a coarse counter, a FIFO memory and an AXI interface, to assemble the pulse measurement unit. A comparison between the default routing implementation and the proposed manual routing has been performed, shown an improvement of 27% on the overall TDC single-shot precision. The implemented TDC achieved a 380 ps RMS resolution, a maximum DNL of 0.38 LSB and a peak-to-peak INL of 0.69 LSB, corresponding to a 21.7% and 70.4% improvement, respectively, when compared to the default design approach.FCT - Fundação para a Ciência e a Tecnologia(037902

All-digital time-to-digital converter design methodology based on structured data paths

Time-to-Digital Converters (TDC) are popular circuits in many applications, where high resolution time measurements are required, for example, in Positron Emission Tomography (PET). Besides its resolution, the TDC's linearity is also an important performance indicator, therefore calibration circuits usually play an important role on TDCs architectures. This paper presents an all-digital TDC implemented using Structured Datapath to reduce the need for calibration circuitry and cells custom design, without compromising the TDC's linearity. The proposed design is fully implementable using a Hardware Description Language (HDL) and enables a complete design flow automation, reducing both development time and system's complexity. The TDC is based on a Delay Locked Loop (DLL) paired with a coarse counter to increase measurement range. The proposed architecture and the design approach have proven to be efficient in developing a high resolution TDC with high linearity. The proposed TDC was implemented in TSMC 0.18 μm CMOS technology process achieving a resolution of 180ps, with Differential Non-Linearity (DNL) and Integral Non-Linearity (INL) under 0.6 LSB.FRCT - Fundo Regional para a Ciência e Tecnologia(PDE/BDE/114562/2016

Technology independent ASIC based time to digital converter

This paper proposes a design methodology for a synthesizable, fully digital TDC architecture. The TDC was implemented using a hardware description language (HDL), which improves portability between platforms and technologies and significantly reduces design time. The proposed design flow is fully automated using TCL scripting and standard CAD tools configuration files. The TDC is based on a Tapped Delay Line architecture and explores the use of Structured Data Path (SDP) as a way to improve the TDL linearity by homogenizing the routing and parasitic capacitances across the multiple TDL’s steps. The studied approach also secures a stable, temperature independent measurement operation. The proposed TDC architecture was fabricated using TSMC 180nm CMOS process technology, with a 50MHz reference clock and a supply voltage of 1.8V. The fabricated TDC achieved an 111ps RMS resolution and a single-shot precision of 54ps (0.48 LSB) and 279ps (2.51 LSB), with and without post-measurement software calibration, respectively. The DNL across the channel is mostly under 0.3 LSB and a maximum of 8 LSB peak-to-peak INL was achieved, when no calibration is applied.- (037902

Influence of mechanical stress in a packaged frequency-modulated MEMS accelerometer

Frequency modulated accelerometers composed of two double-ended tuning fork (DETF) resonators on a differential configuration were characterized for their sensitivity to force applied to their package. Commonly, differential architectures are employed to cancel common mode errors, such as the mechanical stress or temperature dependency. The device dependence to mechanical stress was experimentally measured for forces up to 15 N and a reduction of about 5.6 times was obtained on the differential measurement. Additionally, the silicon dies were glued to chip-carriers using two different glues with distinct properties, and their sensitivity to stress was compared. The effectiveness of a viscoelastic glue over an epoxy-based glue for stress decoupling was tested. Long-term measurements under constant force were experimentally performed and for a time period of approximately 100 min, the stress relaxation and creeping of the viscoelastic glue enabled the recovery to the initial output of the sensor.The first author is supported by FCT - Fundacao para a Ciencia e Tecnologia through the grant PDE/BDE/114564/2016. This work is supported by FCT with the reference project UID/EEA/04436/2019

Dementia in a patient with Thymoma and hypogammaglobulinaemia (Good's syndrome)

Good's syndrome is extremely rare and refers to an acquired B and T cell immunodeficiency in thymoma patients. The authors of this article present a case report of a 75-year-old, caucasian male patient previously subjected to examinations for secondary dementia and recurrent infections, which revealed paraneoplastic syndrome arose from thymoma. He underwent thymectomy, while his immunodeficiency syndrome sustained with frequent opportunistic infections, constantly requiring intravenous immunoglobulin treatment

A922 Sequential measurement of 1 hour creatinine clearance (1-CRCL) in critically ill patients at risk of acute kidney injury (AKI)

Meeting abstrac

Nurses' perceptions of aids and obstacles to the provision of optimal end of life care in ICU

Contains fulltext : 172380.pdf (publisher's version ) (Open Access

Auto-calibrated, thermal-compensated MEMS for smart inclinometers

Tese de Doutoramento - Programa Doutoral em Engenharia Electrónica e de Computadores (PDEEC) - Especialidade de Instrumentação e Microssistemas EletrónicosThe electronic control of a mechanical structure with micro dimensions, offers unique opportunities to exploit the tight coupling between co-integrated micromechanical structures and ICs (=Micro Electro Mechanical Systems (MEMS)). This coupling allows the implementation of integrated data-acquisition systems, with overall functionality or specifications that cannot be met using individually designed structures and circuits. This work focus on the development of a new class of MEMS-based inclinometers that includes electromechanical pre-processing of the mechanical signal in the mechanical domain and thermal compensation. The force-dependent pull-in voltage of a micromechanical structure, due to a sufficiently large electrostatic field, enables the realization of a high-resolution, low-bandwidth inclinometer. Pull-in is characterized by the sudden loss of stability in electrostatically actuated parallel-plate devices. Since pull-in voltage is stable and easy to measure, it enables an effective transduction mechanism that does not require complex readout electronics. A switched capacitor based complementary metal-oxide-semiconductor (CMOS) integrated circuit is developed, fabricated and used to detect the large capacitance change in the MEMS sensing element, while controlling a high-resolution external actuation system. Dedicated MEMS microstructures with extra proof mass show high sensitivity, 269mV/◦ with a non-linearity better than 0.5%FS (Full Scale of ±23◦). The measured noise is limited by the actuation system, rather than the mechanicalthermal white noise of the MEMS device, setting the sensor’s resolution at 75μ◦, high above state-of-the-art MEMS devices. The characteristics of this dedicated MEMS inclinometer system enables an thermal compensation mechanism, which increases the sensor stability to values better than 0.004%FS.O controlo eletrónico de estruturas mecânicas de micro dimensões, oferece oportunidades únicas para a exploração do acoplamento integrado entre microestruturas mecânicas e circuitos integrados (=Micro Electro Mechanical Systems MEMS). Este tipo de acoplamento permite a implementação de sistemas de aquisição de dados integrados, com funcionalidades ou especificações que não poderiam ser atingidas por estruturas ou circuitos desenhados individualmente. Este trabalho foca-se no desenvolvimento de um novo tipo de inclinómetros MEMS que inclui mecanismos de compensação térmica diretamente no domínio mecânico. A tensão de pull-in de uma microestrutura mecânica, possibilita a criação de inclinómetros de elevada resolução e baixa largura de banda. O fenómeno de pullin é caracterizado pela súbita perda de estabilidade em estruturas de elétrodosparalelos, quando electrostaticamente atuadas. Uma vez que a tensão de pull-in é estável e fácil de medir, é possível criar um método de transdução eficiente, sem ser necessário um front-end capacitivo de elevada complexidade. Um circuito integrado, baseado num amplificador de condensadores comutados, é desenvolvido, fabricado e usado para detetar a variação de capacidade no elemento sensorial, ao mesmo tempo que controla o sistema de atuação externo de elevada resolução. As microestruturas fabricadas com uma massa-inercial adicional, demonstraram elevada sensibilidade, 269mV/◦ (não linearidade < 0.5%, escala completa de ±23◦). O ruído medido não foi limitado pelo ruído termomecânico da estrutura, mas sim pelo sistema de atuação, colocando a resolução do sensor em 75μ◦, claramente acima do estado da arte em dispositivos MEMS. As características únicas deste inclinómetro, permitem a implementação de mecanismos de compensação térmica, podendo melhorar a estabilidade do sensor para valores superiores a 0.004%FS

Culturas in vitro de Fontinalis spp. E : ensaios de bioacumulação de ouro e elementos associados

Dissertação de mestrado em Biodiversidade e Biotecnologia Vegetal (Biotecnologia), apresentada à Faculdade de Ciências e Tecnologia da Universidade de Coimbra.Fontinalis antipyretica e F. squamosa são dois musgos aquáticos que crescem submersos em pequenos cursos de água. Foram recolhidos exemplares de ambas as espécies num ribeiro na região centro de Portugal e levadas para o laboratório, onde foram realizados ensaios para obtenção de culturas assépticas. Os resultados mostraram que um tratamento de hipoclorito de cálcio 5% por 3 min. obteve a melhor taxa de esterilização sem efeitos nocivos. Melhores resultados para o estabelecimento de plantas foram obtidos numa solução de Knop modificada, contendo os micronutrientes do meio MS e o Fe do meio MS reduzido a meia força. Uma vez obtido o material vegetal suficiente, foi avaliado o efeito de diferentes concentrações de benziladenina (0,5-4,0 mg.L-1) no crescimento das plantas. Os resultados mostraram que a BA tem um efeito inibitório sobre o crescimento da planta já que em todas as concentrações testadas o comprimento dos explantes foi menor do que o observado no controle (meio sem reguladores de crescimento). Após essas experiências testou-se a capacidade de crescimento de ambas as espécies na presença de ouro, adicionado ao meio de cultura como tetracloroaurato de sódio (III) hidratado (NaAuCl4), em concentrações que variam de 0,5 a 20 μM. Os resultados indicaram que Fontinalis antipyretica mostrou uma taxa de crescimento similar ao controle no meio contendo até 3,75 μM. Concentrações mais elevadas prejudicaram o crescimento das plantas. Fontinalis squamosa apresentou melhor adaptação às concentrações mais elevadas. Também fizemos estudos semelhantes com antimónio, arsénio e prata, elementos frequentemente associados ao ouro com os mesmos intervalos de concentrações. Experiências feitas em aquário durante 30 dias, testaram o comportamento de acumulação das plantas na presença de iodeto de ouro (AuI), cianeto de ouro (AuCN), tetracloroaurato de sódio hidratado (III) (NaAuCl4), tartarato de antimónio (C4H4O7Sb.Na), trióxido de arsénio (As2O3) e nitrato de prata (AgNO3) em três concentrações diferentes. Os resultados obtidos pela técnica de Espectrometria de Absorção Atómica em Câmara de Grafite (GF-AAS), parecem indicar que ambas as plantas são bioabsorventes adequados para ouro, prata e antimónio. Melhores resultados foram obtidos com solução de iodeto. Análises de microscopia não foram conclusivas para entender como os tecidos interagem com o metal.Fontinalis antipyretica and F. squamosa are two water mosses growing underwater in small water courses. Stems of both species were collected in a brook in the centre region of Portugal and brought to the laboratory where attempts to obtain aseptic cultures were performed. The results showed that a 5% calcium hypochlorite treatment for 3 min. gave the best rate of sterilization without harmful effects. Best results for plant establishment were achieved in a Knop modified solution containing the minor salts of the MS medium and the Fe of the MS medium reduced at half strength. Once enough plant material was obtained the effect of different concentrations of the benzyladenine (0.5 – 4.0 mg.L-1) on plant growth was evaluated. The results showed that BA has an inhibitory effect on plant growth since in all the concentrations tested shoot length was lower than that observed in the control (medium without plant growth regulators). Following these experiments we have tested the ability of both species to growth in the presence of gold added to the growth medium as sodium tetrachloroaurate (III) hydrate (NaAuCl4) in concentrations ranging from 0,5 to 20 μM. The results indicated that Fontinalis antipyretica showed a growth rate similar to the control on media containing until 3.75 μM. Higher concentrations impaired plant growth. Fontinalis squamosa showed better adaptation to higher concentrations. We also made similar studies with elements often associated with gold, arsenic, antimony and silver with the same concentrations range. Experiments made in aquarium over 30 days tested the accumulation behavior of the plants in the presence of gold iodide (AuI), gold cyanide (AuCN), sodium tetrachloroaurate (III) hydrate (NaAuCl4), antimonium tartaricum (C4H4O7Sb.Na), arsenic trioxide (As2O3) and silver nitrate (AgNO3) in three different concentrations. The results obtained with GF-AAS (Graphite Furnace Atomic Absortion Spectrometry) technique seem to indicate that both plants are suitable biosorbents for gold, silver and antimony. Better results were obtained with iodide solution. Microscopy analyses were not conclusive to understand how the tissues cope with the metal

Recent developments and challenges in FPGA-Based time-to-digital converters

Over the past few years, the gap between field-programmable gate array (FPGA) and application-specific integrated circuit (ASIC) performance levels has been narrowed due to the constant development of FPGA technology. The high performance, together with the lower development costs and a shorter time to market, turns FPGA-based platforms attractive for a huge range of applications, among them time-To-digital converters (TDCs). It is, therefore, important to analyze the evolution of FPGA-based TDCs to better understand where the research efforts should be focused in the near future. This article presents and discusses the improvements on the FPGA-based TDC research, aiming to be a starting point for new studies on this field, with some guidelines for future research. A state-of-The-Art literature review on the FPGA-based TDC is presented, aiming to categorize and discuss the existing architectures. This discussion addresses architectures' characteristics, limitations, and areas of application.FRCT - Fundo Regional para a Ciência e Tecnologia(PDE/BDE/114562/2016