Artículos (Electrónica y Electromagnetismo)

URI permanente para esta colecciónhttps://hdl.handle.net/11441/10839

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  • Acceso AbiertoArtículo
    Resonantly induced transparency for metals with low angular dependence
    (American Institute of Physics, 2016-12-15) Camacho Aguilar, Miguel; Hibbins, Alastair P.; Sambles, J. Roy; Universidad de Sevilla. Departamento de Electrónica y Electromagnetismo; Engineering and Physical Sciences Research Council (UK); Universidad de Sevilla. TIC112: Microondas
    Thin (sub skin-depth) metal layers are known to almost completely reflect radiation at microwave frequencies. It has previously been shown that this can be overcome at resonance via the addition of closely spaced periodic structures on either side of the film. In this work, we have extended the original one-dimensional impedance mechanism to the use of two-dimensional periodic structures both experimentally and analytically using an equivalent circuit approach. The resulting device shows experimentally a low (<5% relative frequency shift) dependence in both angle of incidence and polarisation. We also show that the same principle can be used to transmit through a thicker (∼μm) perfectly conducting film perforated with a non-diffracting (short pitch) array of subwavelength holes with the cut-off frequency above 900 GHz showing resonant transmissivities in the 20–30 GHz range above 40%.
  • Acceso AbiertoArtículo
    A single inverse-designed photonic structure that performs parallel computing
    (Springer Nature, 2021-03-05) Camacho Aguilar, Miguel; Edwards, Brian; Engheta, Nader; Universidad de Sevilla. Departamento de Electrónica y Electromagnetismo; Engheta, Nader; Office of Naval Research (ONR). United States; Universidad de Sevilla. TIC112: Microondas
    In the search for improved computational capabilities, conventional microelectronic computers are facing various problems arising from the miniaturization and concentration of active electronics. Therefore, researchers have explored wave systems, such as photonic or quantum devices, for solving mathematical problems at higher speeds and larger capacities. However, previous devices have not fully exploited the linearity of the wave equation, which as we show here, allows for the simultaneous parallel solution of several independent mathematical problems within the same device. Here we demonstrate that a transmissive cavity filled with a judiciously tailored dielectric distribution and embedded in a multi-frequency feedback loop can calculate the solutions of a number of mathematical problems simultaneously. We design, build, and test a computing structure at microwave frequencies that solves two independent integral equations with any two arbitrary inputs and also provide numerical results for the calculation of the inverse of four 5 x 5 matrices.
  • Acceso AbiertoArtículo
    Alternative General Fitting Methods for Real-Time Cell-Count Experimental Data Processing
    (Institute of Electrical and Electronics Engineers, 2020-07-20) Serrano Viseas, Juan Alfonso; Pérez García, Pablo; Huertas Sánchez, Gloria; Yúfera García, Alberto; Universidad de Sevilla. Departamento de Tecnología Electrónica; Universidad de Sevilla. Departamento de Electrónica y Electromagnetismo; Ministerio de Ciencia, Innovación y Universidades (MICINN). España
    This paper reports two general methods for extraction of cell-electrode electrical model parameters in cell culture (CC) assays. The presented approaches can be applied to CC assays based on electrical cell-substrate impedance spectroscopy (ECIS) technique for real-time supervision, providing the cell number per square centimeter, i.e., the cell density, as main result. Both of the proposed methods - minimization of system equations and data predictive model - search, during the experiment, the optimum values of the electrical model parameters employed for the electrode-cell model. The results of this search enable a fast and efficient calculation of the involved cell-electrode model parameters and supply real-time information on the cell number. For the sake of experimental validation, we applied the proposed methods to practical CCs in cell growth assays with a cell line of AA8 Chinese hamster ovarian fibroblasts and the Oscillation Based Test technique for bioimpedance measurements. These methods can be easily extrapolated to any general cell lines and/or other bioimpedance test methodologies.
  • Acceso AbiertoArtículo
    Bioimpedance Spectroscopy-Based Edema Supervision Wearable System for Noninvasive Monitoring of Heart Failure
    (Institute of Electrical and Electronics Engineers, 2023-05-17) Fernández Scagliusi, Santiago Joaquín; Giménez Miranda, Luis; Pérez García, Pablo; Martín Fernández, Daniel; Medrano Ortega, Francisco Javier; Huertas Sánchez, Gloria; Yúfera García, Alberto; Universidad de Sevilla. Departamento de Tecnología Electrónica; Universidad de Sevilla. Departamento de Medicina; Universidad de Sevilla. Departamento de Electrónica y Electromagnetismo; Universidad de Sevilla. Departamento de Biología Celular; Ministerio de Ciencia, Innovación y Universidades (MICINN). España; Instituto de Salud Carlos III
    Heart failure (HF) is a complex syndrome in which the heart is unable to pump enough blood containing oxygen and nutrients to meet the body's demands. HF is the leading cause of hospitalization for patients over 65 years of age. After a patient is diagnosed with HF, the mortality rate is 50% within the first five years. Presently, there are no unanimous diagnostic criteria for HF. Bioimpedance (BI) analysis has been proposed in recent years as a technique to detect one of the main symptoms: changes in body volume due to edema. This research presents a portable device (Volum), capable of performing real-time BI measurements in a low-cost and noninvasive way. The goal is to improve patient monitoring at home to ensure rapid intervention in cases of worsening conditions, either with timely hospitalizations or adjustments to a patient's usual treatment. Volum is a small, wearable, wireless, lightweight, low-power clinical pilot prototype that takes measurements through four electrodes and sends the data via Bluetooth to an Android device.
  • Acceso AbiertoArtículo
    A Plethysmography Capacitive Sensor for Real-Time Monitoring of Volume Changes in Acute Heart Failure
    (Institute of Electrical and Electronics Engineers, 2021-06-23) Rando, Enrique; Pérez García, Pablo; Scagliusi, Santiago F.; Medrano Ortega, Francisco Javier; Huertas Sánchez, Gloria; Yúfera García, Alberto; Universidad de Sevilla. Departamento de Tecnología Electrónica; Universidad de Sevilla. Departamento de Medicina; Universidad de Sevilla. Departamento de Electrónica y Electromagnetismo; Ministerio de Ciencia, Innovación y Universidades (MICINN). España; Instituto de Salud Carlos III
    A small, wearable, low-weight, and low-power-consumption device for plethysmography capacitive sensing is proposed herein. The device allows carrying out real-time monitoring of leg volume changes in patients suffering from heart failure (HF) conditions. The dynamic of fluid overload in patients with acute HF serves as a prognosis marker for this type of severe disease and, consequently, these patients can benefit from a wearable monitoring system to measure their body volume evolution during and after hospitalization. Our approach is based on contactless capacitive wearable structures implemented by two different sensor realizations located in the ankle: 180°-parallel capacitor plates (two modes of operations are compared, with the patient's body connected to ground and to the average voltage between plates) and planar-parallel capacitor plates whose overlapped surface varies with the volume of the patient's leg. Both realizations exhibit good sensitivity to leg volume changes. The acquisition of capacitance values is performed via a simple circuit that achieves notable performance in simulated volume analysis. A preliminary pilot clinical prototype is described as well.
  • Acceso AbiertoArtículo
    A Multilevel Bottom-Up Optimization Methodology for the Automated Synthesis of RF Systems
    (IEEE. Institute of Electrical and Electronics Engineers, 2019-01-01) Passos, Fabio; Roca, Elisenda; Sieiro, Javier; Fiorelli, Rafaella; Castro López, Rafael; López Villegas, José María; Fernández Fernández, Francisco Vidal; Universidad de Sevilla. Departamento de Electrónica y Electromagnetismo
    In recent years there has been a growing interest in electronic design automation methodologies for the optimization- based design of radiofrequency circuits and systems. While for simple circuits several successful methodologies have been proposed, these very same methodologies exhibit significant deficiencies when the complexity of the circuit is increased. The majority of the published methodologies that can tackle radiofrequency systems are either based on high-level system specification tools or use models to estimate the system performances. Hence, such approaches do not usually provide the desired accuracy for RF systems. In this work, a methodology based on hierarchical multilevel bottom-up design approaches is presented, where multi-objective optimization algorithms are used to design an entire radiofrequency system from the passive component level up to the system level. Furthermore, each level of the hierarchy is simulated with the highest accuracy possible: electromagnetic simulation accuracy at device-level and electrical simulations at circuit/system-level.
  • Acceso AbiertoArtículo
    The role of particle-electrode wall interactions in mobility of active Janus particles driven by electric fields
    (Elsevier, 2025-06-15) M.Boymelgreen, A.; Kunti, G.; García Sánchez, Pablo; Ramos Reyes, Antonio; Yossifon, G.; Miloh, T.; Universidad de Sevilla. Departamento de Electrónica y Electromagnetismo; Ministerio de Ciencia e Innovación (MICIN). España
    Hypothesis The interaction of active particles with walls can explain discrepancies between experiments and theory derived for particles in the bulk. For an electric field driven metallodielectric Janus particle (JP) adjacent to an electrode, interaction between the asymmetric particle and the partially screened electrode yields a net electrostatic force – termed self-dielectrophoresis (sDEP) - that competes with induced-charge electrophoresis (ICEP) to reverse particle direction. Experiments The potential contribution of hydrodynamic flow to the reversal is evaluated by visualizing flow around a translating particle via micro-particle image velocimetry and chemically suppressing ICEP with poly(l-lysine)-g-poly(ethylene glycol) (PLL-PEG). Mobility of Polystyrene-Gold JPs is measured in KCl electrolytes of varying concentration and with a capacitive SiO2 coating at the metallic JP surface or electrode. Results are compared with theory and numerical simulations accounting for electrode screening. Findings PLL-PEG predominantly suppresses low-frequency mobility where propulsive electro-hydrodynamic jetting is observed; supporting the hypothesis of an electrostatic driving force at high frequencies. Simulations and theory show the magnitude, direction and frequency dispersion of JP mobility are obtained by superposition of ICEP and sDEP using the JP height and capacitance as fitting parameters. Wall proximity enhances ICEP and sDEP and manifests a secondary ICEP charge relaxation time dominating in the contact limit.
  • Acceso AbiertoArtículo
    Synthesis of mm-Wave Wideband Receivers in 28-nm CMOS Technology for Automotive Radar Applications
    (IEEE, 2020-03-26) Moreira de Passos, Fabio; Chanca, Miguel; Roca, Elisenda; Castro-López, Rafael; Fernández Fernández, Francisco Vidal; Universidad de Sevilla. Departamento de Electrónica y Electromagnetismo
    A new strategy for millimeter-wave (mm-Wave) circuit and system synthesis, where the accuracy of electromagnetic simulations can be achieved in optimization-based design methodologies without sacrificing efficiency, is presented and tested within a real industrial project. This is done by properly partitioning the system, generating libraries of passive devices which are electromagnetically simulated prior to any circuit optimization, generating performance tradeoffs at different hierarchical levels with multiobjective optimization algorithms and hierarchically composing lower level sub-blocks. With this proposed solution, an entire mm-Wave system, from the passive component level up to the system level, has been designed and compared with the results obtained from a conventional design approach, demonstrating the outstanding capabilities of the methodology.
  • Acceso AbiertoArtículo
    Continuous Focusing of Particles by AC-Electroosmosis and Induced Dipole Interactions
    (ACS Publications, 2024) Wiegerinck, Harm T. M.; Wood, Jeffery A.; Eijkel, Jan C.T.; Lammertink, Rob G. H.; Frankel, Itzchak; Ramos Reyes, Antonio; Universidad de Sevilla. Departamento de Electrónica y Electromagnetismo; Dutch Research Council (NWO); Universidad de Sevilla. FQM253: Electrohidrodinámica y Medios granulares cohesivos
    Continuous particle focusing by using microfluidics is an effective method for separating particles, cells, or droplets for analytical purposes. Previously, it was shown that an alternating current across rectangular microchannels with slightly deformed side walls results in vortex flow patterns caused by alternating current electroosmosis (AC-EOF) and could lead to particle focusing. In this work, we explore this mechanism by experimentally studying the particle focusing behavior for various fluid flow velocities through a microchannel. Since it is unlikely that the particles are kept in their focused position solely by convection, a theoretical force balance between the hydrodynamic and the induced dipole force was determined. In our experiments, it was found that there is no substantial effect of the pressure-driven fluid velocity on the particle focusing velocity within the studied range. From the theoretical force balance calculations, it was determined that while the addition of the induced dipole force can still not completely describe the experimentally observed particle focusing, the induced dipole can be strong enough to overcome the hydrodynamic force. Finally, it is hypothesized that under specific circumstances, including a repulsive electrostatic force between a particle and electrode wall can complete the theoretical particle focusing force balance. Alternative phenomena that could also play a role in particle focusing are proposed.
  • Acceso AbiertoArtículo
    Symmetry and Finite-Size Effects in Quasi-Optical Extraordinarily THz Transmitting Arrays of Tilted Slots
    (IEEE, 2020) Camacho Aguilar, Miguel; Nekovic, Ajla; Freer, Suzanna; Penchev, Pavel; Rodríguez Boix, Rafael; Dimov, Stefan; Navarro Cía, Miguel; Universidad de Sevilla. Departamento de Electrónica y Electromagnetismo
    Extraordinarily transmitting arrays are promising candidates for quasi-optical (QO) components due to their high frequency selectivity and beam scanning capabilities owing to the leaky-wave mechanism involved. We show here how by breaking certain unit cell and lattice symmetries, one can achieve a rich family of transmission resonances associated with the leaky-wave dispersion along the surface of the array. By combining 2-D and 1-D periodic method of moments (MoM) calculations with QO terahertz (THz) time-domain measurements, we provide physical insights, numerical, and experimental demonstration of the different mechanisms involved in the resonances associated with the extraordinary transmission peaks and how these evolve with the number of slots. Thanks to the THz instrument used, we are also able to explore the time-dependent emission of the different frequency components involved.
  • Acceso AbiertoArtículo
    Role of particle size on the cohesive behavior of limestone powders at high temperature
    (Elsevier, 2020) Espín Milla, Manuel Jesús; Durán Olivencia, Francisco José; Valverde Millán, José Manuel; Universidad de Sevilla. Departamento de Electrónica y Electromagnetismo; Universidad de Sevilla. Departamento de Física Aplicada II; Ministerio de Economía y Competitividad (MINECO). España
    Thermal Energy Storage (TES) using granular solids is gaining momentum in the last years. With no degradation up to very high temperatures and very low price the use of some granular materials such as sand or SiC would be feasible for storing sensible heat at large scale. A further step beyond TES is thermochemical energy storage (TCES) wherein the granular solids undergo a highly endothermic reaction at high temperature. Energy can be in this way more efficiently stored in the long term and released on demand by means of the reverse exothermic reaction. The Calcium Looping process, based on the calcination/carbonation of CaCO3, is being actively investigated for this purpose. However, a caveat of using granular solids for energy storage is the possible increase of interparticle adhesive forces with temperature which would severely hamper the flowability of the solids in the process. The cohesiveness of granular materials is essentially determined by particle size. In this paper we investigate the dependence of the tensile yield strength and compressibility of CaCO3 powders on temperature and consolidation stress using samples of narrow particle size distribution in the relevant range between ∼30 and ∼80μm particle size and temperatures up to 500°C. Our experimental results show that powder cohesiveness is greatly increased with temperature especially in the case of the finest powders whose tensile yield strength can be increased by up 2 orders of magnitude. The increase of cohesiveness with temperature is further enhanced with a previously applied consolidation stress, which is particularly relevant for applications wherein large amounts of solids are to be stored at high temperature. Experimental data are consistent with the predictions by a contact mechanics model assuming that the solids deform plastically at interparticle contacts. A main conclusion from our work is that some mechanical properties of the solids, specially the mechanical hardness, and how they change with temperature, play a critical role on the flowability of the solids as affected by an increase of temperature.
  • Acceso AbiertoArtículo
    Low-pressure calcination to enhance the calcium looping process for thermochemical energy storage
    (Elsevier, 2022-05-30) Ortiz Domínguez, Carlos; Carro Paulete, Andrés; Chacartegui, Ricardo; Valverde Millán, José Manuel; Perejón Pazo, Antonio; Sánchez-Jiménez, P. E.; Pérez Maqueda, Luis Allan; Universidad de Sevilla. Departamento de Electrónica y Electromagnetismo; Universidad de Sevilla. Departamento de Ingeniería Energética; Ministerio de Economía y Competitividad (MINECO). España; European Union (UE); Junta de Andalucía
    The Calcium-Looping (CaL) process, based on the multicyclic calcination-carbonation of CaCO3/CaO, is considered a promising Thermochemical Energy Storage (TCES) technology to be integrated into Concentrating Solar Power (CSP) plants. This work proposes a novel CaL integration that operates at low-pressure calcination under pure CO2 and a moderated temperature. Low-pressure calcination (0.01 bar) provides a suitable solution to mitigate CaO sintering and its consequent loss of reactivity in the carbonation stage. Since the temperature for quick calcination in a pure CO2 atmosphere is decreased (from around 950 °C at 1 bar to 765 °C at 0.01 bar), the energy losses at the receiver are minimised. In addition, a reduced calcination temperature allows for the use of metallic receivers already tested at the MW-scale, which significantly increases the CSP-CaL integration reliability. Moreover, multicycle CaO reactivity is promoted in short residence times, allowing the use of a simpler reactor design. Furthermore, there is an increase of 85% in the energy storage density of the system. The proposed plant proposes a smooth integration of the CaL process in CSP plants, with a moderate storage level and supported by a natural gas backup system (solar share higher than 50%). The results show that the solar thermal-to electric efficiency is above 30%.
  • EmbargoArtículo
    Partial Oxycombustion-Calcium Looping hybridisation for CO2 capture in Waste-to-Energy power plants
    (Elsevier, 2023-03-28) Ortiz Domínguez, Carlos; García-Luna, S.; Chacartegui, Ricardo; Valverde Millán, José Manuel; Pérez Maqueda, Luis Allan; Universidad de Sevilla. Departamento de Electrónica y Electromagnetismo; Universidad de Sevilla. Departamento de Ingeniería Energética; Valverde Millán, José Manuel; Junta de Andalucía
    Integrating bioenergy and carbon capture and storage (BECCS) presents a great opportunity for power production with negative global CO2 emissions. This work explores a novel synergetic system that integrates membranes, partial biomass oxycombustion and the calcium looping (CaL) process. Polymeric membranes generate oxygen-enriched air (OEA) with an O2 concentration of 39%v/v, which is used for partial oxycombustion of biomass waste. The CO2-enriched flue gas evolves from the waste-to-energy plant to the CaL unit, where CO2 concentration is increased up to 90–95%v/v, ready for purification and sequestration. Compared to only oxycombustion systems, the proposed concept presents fewer technological challenges in retrofitting boilers to waste-to-energy plants. Moreover, this new approach is highly efficient as integrating membranes to produce OEA instead of cryogenic distillation systems significantly reduces energy consumption. A novel integration concept is modelled to evaluate the whole process efficiency and the effect of key parameters on the system performance, such as the temperature of the reactors, the membrane surface area, and the partial oxy-combustion degree. The results show that the so-called mOxy-CaL system has an energy consumption associated with CO2 capture below 4 MJ/kg CO2 (a 31% lower than that for a conventional CaL process), with a higher CO2 capture efficiency than oxycombustion and the CaL process separately. On the other hand, the economic analysis shows a higher CO2 capture cost for the novel configuration than for the typical CaL configuration due to the additional investment cost of the membrane system. Improvements in membrane performance by increasing its permeance and diminishing the required surface area would significantly reduce the economic cost of this novel integration. Using membranes with permeance over 400 GPU would boost the system's competitiveness.
  • Acceso AbiertoArtículo
    Integrated sensors for electric stimulation of stem cells: A review on microelectrode arrays (MEAs) based systems
    (Elsevier, 2025-06) Algarín Pérez, Antonio; Martín Fernández, Daniel; Daza Navarro, María Paula; Huertas Sánchez, Gloria; Yúfera García, Alberto; Universidad de Sevilla. Departamento de Biología Celular; Universidad de Sevilla. Departamento de Electrónica y Electromagnetismo; Universidad de Sevilla. Departamento de Tecnología Electrónica; Ministerio de Ciencia e Innovación (MICIN). España
    This paper provides an update on the sensors and actuators involved in Stem Cells (SC) differentiation processes based on electric stimulation (STIM), including both current and future progress. These techniques are applied in a range of biological and medical protocols, including cell linage derivation, tissue engineering, cellular therapy, cancer research, and cell motility. The typical methodology of SC electric STIM endeavors to emulate biological processes by applying an electrical signal to the cell culture and evaluating the cell response. Cell metabolism is electrically sensitive, responding in some manner to a given stimulus. The precise mechanism by which this occurs is not fully understood, but it is evident that changes in ion density at the cell membrane proximity must excite the cell metabolism (receptors), thereby activating its “differentiation” in response. In order to gain a deeper insight into the cellular mechanisms involved in this process, the physical variables should be better recognized, measured, and quantified during the protocol execution. This work is contributing to the development of a compilation of proposed systems, and specifications required, to identify and better understand the local conditions within the cell environment that are responsible for the activation of the differentiation processes. It is crucial that STIM systems are optimally designed and that the cell response is correctly understood. Two features will be reviewed: the setup employed and the circuits for STIM and monitoring. The nexus between these two elements are the electrodes, and this work will therefore be devoted to the realization of integrated Micro-Electrode Arrays (MEAs), and the design problems associated with it. The focus will be on MEAs, with the same size scale as the cells, and the design issues related to integrated electrodes, under electric stimulation, voltage or current modes.
  • Acceso AbiertoArtículo
    A comparative analysis of VLSI trusted virtual sensors
    (Elsevier, 2018-06-15) Martínez Rodríguez, Macarena Cristina; Brox Jiménez, Piedad; Baturone Castillo, María Iluminada; Universidad de Sevilla. Departamento de Electrónica y Electromagnetismo; Ministerio de Economía y Competitividad (MINECO). España; European Union (UE); Consejo Superior de Investigaciones Científicas (CSIC)
    This paper analyzes three cryptographic modules suitable for digital designs of trusted virtual sensors into integrated circuits, using 90-nm CMOS technology. One of them, based on the keyed-hash message authentication code (HMAC) standard employing a PHOTON-80/20/16 lightweight hash function, ensures integrity and authentication of the virtual measurement. The other two, based on CAESAR (the Competition for Authenticated Encryption: Security, Applicability, and Robustness) third-round candidates AEGIS-128 and ASCON-128, ensure also confidentiality. The cryptographic key required is not stored in the sensor but recovered in a configuration operation mode from non-sensitive data stored in the non-volatile memory of the sensor and from the start-up values of the sensor SRAM acting as a Physical Unclonable Function (PUF), thus ensuring that the sensor is not counterfeit. The start-up values of the SRAM are also employed in the configuration operation mode to generate the seed of the nonces that make sensor outputs different and, hence, resistant to replay attacks. The configuration operation mode is slower if using CAESAR candidates because the cryptographic key and nonce have 128 bits instead of the 60 bits of the key and 32 bits of the nonce in HMAC. Configuration takes 416.8 µ s working at 50 MHz using HMAC and 426.2 µ s using CAESAR candidates. In the other side, the trusted sensing mode is much faster with CAESAR candidates with similar power consumption. Trusted sensing takes 212.62 µ s at 50 MHz using HMAC, 0.72 µ s using ASCON, and 0.42 µ s using AEGIS. AEGIS allows the fastest trusted measurements at the cost of more silicon area, 4.4 times more area than HMAC and 5.4 times more than ASCON. ASCON allows fast measurements with the smallest area occupation. The module implementing ASCON occupies 0.026 mm2 in a 90-nm CMOS technology.
  • Acceso AbiertoArtículo
    Unified RTN and BTI statistical compact modeling from a defect-centric perspective
    (Elsevier, 2021-11) Pedreira, G.; Martín-Martínez, Javier; Saraza Canflanca, Pablo; Roca, Elisenda; Fernández Fernández, Francisco Vidal; Nafria, M.; Universidad de Sevilla. Departamento de Electrónica y Electromagnetismo; Agencia Estatal de Investigación (AEI)
    In nowadays deeply scaled CMOS technologies, time-dependent variability effects have become important concerns for analog and digital circuit design. Transistor parameter shifts caused by Bias Temperature Instability and Random Telegraph Noise phenomena can lead to deviations of the circuit performance or even to its fatal failure. In this scenario extensive and accurate device characterization under several test conditions has become an unavoidable step towards trustworthy implementing the stochastic reliability models. In this paper, the statistical distributions of threshold voltage shifts in nanometric CMOS transistors will be studied at near threshold, nominal and accelerated aging conditions. Statistical modelling of RTN and BTI combined effects covering the full voltage range is presented. The results of this work suppose a complete modelling approach of BTI and RTN that can be applied in a wide range of voltages for reliability predictions.
  • Acceso AbiertoArtículo
    Improving the reliability of SRAM-based PUFs under varying operation conditions and aging degradation
    (Elsevier, 2021-03) Saraza Canflanca, Pablo; Carrasco-López Héctor; Santana-Andreo, Andrés; Brox Jiménez, Piedad; Castro-López, Rafael; Roca, Elisenda; Fernández Fernández, Francisco Vidal; Universidad de Sevilla. Departamento de Electrónica y Electromagnetismo; Agencia Estatal de Investigación (AEI); Ministerio de Ciencia, Innovación y Universidades (MICINN). España
    The utilization of power-up values in SRAM cells to generate PUF responses for chip identification is a subject of intense study. The cells used for this purpose must be stable, i.e., the cell should always power-up to the same value (either ‘0’ or ‘1’). Otherwise, they would not be suitable for the identification. Some methods have been presented that aim at increasing the reliability of SRAM PUFs by identifying the strongest cells, i.e., the cells that more consistently power-up to the same value. However, these methods present some drawbacks, in terms of either their practical realization or their actual effectiveness in selecting the strongest cells at different scenarios, such as temperature variations or when the circuits have suffered aging-related degradation. In this work, the experimental results obtained for a new method to classify the cells according to their power-up strength are presented and discussed. The method overcomes some of the drawbacks in previously reported methods. In particular, it is experimentally demonstrated that the technique presented in this work outstands in selecting SRAM cells that are very robust against circuit degradation and temperature variations, which ultimately translates into the construction of reliable SRAM-based PUFs.
  • Acceso AbiertoArtículo
    Insights Into the Dynamics of Coupled VO2 Oscillators for ONNs
    (IEEE, 2021-05-31) Nuñez Martinez, Juan; Quintana Toledo, José María; Avedillo de Juan, María José; Jiménez, Manuel; Todri-Sanial, Aida; Linares-Barranco, Bernabe; Universidad de Sevilla. Departamento de Electrónica y Electromagnetismo; European Union (UE); Ministerio de Economía y Competitividad (MINECO). España
    The collective behavior of many coupled oscillator systems is currently being explored for the implementation of different non-conventional computing paradigms. In particular, VO2 based nano-oscillators have been proposed to implement oscillatory neural networks that can serve as associative memories, useful in pattern recognition applications. Although the dynamics of a pair of coupled oscillators have already been extensively analyzed, in this brief, the topic is addressed more practically. Firstly, for the application mentioned above, each oscillator needs to be initialized in a given phase to represent the input pattern. We demonstrate the impact of this initialization mechanism on the final phase relationship of the oscillators. Secondly, such oscillatory networks are based on frequency synchronization, in which the impact of variability is critical. We carried out a comprehensive mathematical analysis of a pair of coupled oscillators taking into account both issues, which is a first step towards the design of the oscillatory neural networks for associative memory applications.
  • Acceso AbiertoArtículo
    An Efficient Transformer Modeling Approach for mm-Wave Circuit Design
    (Elsevier, 2021-01) Moreira de Passos, Fabio; Roca, Elisenda; Sieiro, Javier; Castro-López, Rafael; Fernández Fernández, Francisco Vidal; Universidad de Sevilla. Departamento de Electrónica y Electromagnetismo; Agencia Estatal de Investigación (AEI)
    In this paper, a Gaussian-process surrogate modeling methodology is used to accurately and efficiently model transformers, which are still a bottleneck in radio-frequency and millimeter-wave circuit design. The proposed model is useful for a wide range of frequencies from DC up to the millimeter-wave range (over 100 GHz). The technique is statistically validated against full-wave electromagnetic simulations. The efficient model evaluation enables its exploitation in iterative user-driven design approaches, as well as automated design exploration involving thousands of simulations. As experimental results, the model is used in several scenarios, such as the design of an inter-stage amplifier operating at 60 GHz, where the model assisted in the simulation of the transformers and baluns used, and the design of individual transformers and a matching network.
  • Acceso AbiertoArtículo
    Induced-charge Electrophoresis of a Tilted Metal Nanowire Near an Insulating Wall
    (American Physical Society, 2024) Flores Mena, Jose Eladio; García Sánchez, Pablo; Ramos Reyes, Antonio; Universidad de Sevilla. Departamento de Electrónica y Electromagnetismo; Benemérita Universidad Autónoma de Puebla
    Electric fields are commonly used to control the orientation and motion of microscopic metal particles in aqueous suspensions. For example, metallodielectric Janus spheres are propelled by the induced-charge electro-osmotic flow occurring on their metallic side, the most common case in electrokinetics of exploiting symmetry breaking of surface properties for achieving net particle motion. In this work, we demonstrate that a homogeneous metal rod can translate parallel to a dielectric wall as a result of the hydrodynamic wall-particle interaction arising from the induced-charge electro-osmosis on the rod surface. The applied electric field could be either dc or low-frequency ac. The only requirement for a nonvanishing particle velocity is that the axis of the rod be inclined with respect to the wall, i.e., it cannot be neither parallel nor perpendicular. We show numerical results of the rod velocity as a function of rod orientation and distance to the wall. The maximum particle velocity is found for an orientation of between ∼30° and ∼50°, depending on the position and aspect ratio of the cylinder. Particle velocities of up to tens of μm/s are predicted for typical conditions in electrokinetic experiments.