Contributions to the development of microwave active circuits: metamaterial dual-band active filters and broadband differential low-noise amplifier

New telecommunication systems require electronic components with increasing performance. Microwave active circuits are not an exception. In fact, these active devices (such as amplifiers, active filters, oscillators, mixers, switches, modulators, etc.) are a key part of any modern communication device and, in many cases, the components that greatly limit the overall system performance. During the last decades, engineers have been improving the performance and operation capabilities of such active components, in order to satisfy the new requirements that novel communication services were demanding. This development has taken place in two distinct lines of action. The first line deals with the optimization of the fabrication process of the transistors, which are the basic components in most active circuits. This physical improvement usually translates into higher transconductance, lower noise gure or operation at higher frequencies. The other line is related with the circuit topology in which the transistor is embedded. This second aspect handles the interaction of the transistor with other additional components or transmission lines and provides the desired operation (e.g., amplification, oscillation, etc.). This thesis is more related with the last aspect, in which the use of novel active circuit topologies is investigated. Two main research lines are presented. In the first line, novel dual-band active filter topologies are proposed. This multiband response is achieved by the use of metamaterial structures. In the second one, the use of differential low noise amplifiers is proposed for the design of active antenna arrays. The intended application is the development of a broadband active antenna array demonstrator for radio-astronomy applications

Developing a smartphone app based on the unified protocol for the transdiagnostic treatment of emotional disorders: a qualitative analysis of users and professionals' perspectives

Emotional Disorders have become the most prevalent mental disorders in the world. In relation to their high prevalence, mental health care from public health services faces major challenges. Consequently, finding solutions to deliver cost-effective evidence-based treatments has become a main goal of today's clinical psychology. Smartphone apps for mental health have emerged as a potential tool to deal with it. However, despite their effectiveness and advantages, several studies suggest the need to involve patients and professionals in the design of these apps from the first stage of the development process. Thus, this study aimed to identify, from both a group of users and professionals, the needs, opinions, expectations and design aspects of a future smartphone app based in the Unified Protocol (UP), that will allow to develop the subsequent technical work of the app engineers. Two focus groups were conducted, one with 7 professionals and the other with 9 users, both groups familiar with the UP. A thematic content analysis based in grounded theory was performed in order to define emergent categories of analysis derived from the interview data. The results revealed 8 common topics in both focus groups and 5 specific key topics were identified in the professionals' focus group. Of the total proposals, 93 % of the professionals' and 78 % of the users' are implemented in the preliminary version of the app

Mejora de la docencia práctica de asignaturas con contenidos de electrónica digital

Memoria ID-0320. Ayudas de la Universidad de Salamanca para la innovación docente, curso 2014-2015

Modelling of Thermal Boundary Resistance in a GaN Diode by means of Electro-Thermal Monte Carlo Simulations

In this paper we evaluate heat diffusion in an AlGaN/GaN diode through a Monte Carlo simulator by expanding its capabilities with the implementation of two thermal methods. We present the impact on the device temperature of considering different substrates and die dimensions. We also evaluate the influence of the thermal boundary resistance (TBR) that appears in the growth process of dissimilar materials. We analyse the effect of the TBR when the diode is grown on two substrates, Si and SiC. As a conclusion, we can state that the TBR is a limiting factor to the thermal flow that becomes more relevant for substrates with high thermal conductivities

Electrónica digital: adquisición de material para la docencia práctica

Memoria ID-0160. Ayudas de la Universidad de Salamanca para la innovación docente, curso 2015-2016

Time-frequency analysis based on minimum-norm spectral estimation to detect induction motor faults

Producción CientíficaIn this work, a new time-frequency tool based on minimum-norm spectral estimation is introduced for multiple fault detection in induction motors. Several diagnostic techniques are available to identify certain faults in induction machines; however, they generally give acceptable results only for machines operating under stationary conditions. Induction motors rarely operate under stationary conditions as they are constantly affected by load oscillations, speed waves, unbalanced voltages, and other external conditions. To overcome this issue, different time-frequency analysis techniques have been proposed for fault detection in induction motors under non-stationary regimes. However, most of them have low-resolution, low-accuracy or both. The proposed method employs the minimum-norm spectral estimation to provide high frequency resolution and accuracy in the time-frequency domain. This technique exploits the advantages of non-stationary conditions, where mechanical and electrical stresses in the machine are higher than in stationary conditions, improving the detectability of fault components. Numerical simulation and experimental results are provided to validate the effectiveness of the method in starting current analysis of induction motors.Consejo Nacional de Ciencia y Tecnología (Proyecto 487058)Universidad de Guanajuato (Proyecto 248495/2019

Self-consistent electro-thermal simulations of AlGaN/GaN diodes by means of Monte Carlo method

In this contribution we present the results from the simulation of an AlGaN/GaN heterostructure diode by means of a Monte Carlo tool where thermal effects have been included. Two techniques are investigated: (i) a thermal resistance method (TRM), and (ii) an advanced electro-thermal model (ETM) including the solution of the steady-state heat diffusion equation. Initially, a systematic study at constant temperature is performed in order to calibrate the electronic model. Once this task is performed, the electro-thermal methods are coupled with the Monte Carlo electronic simulations. For the TRM, several values of thermal resistances are employed, and for the ETM method, the dependence on the thermal-conductivity, thickness and die length is analyzed. It is found that the TRM with well-calibrated values of thermal resistances provides a similar behavior to ETM simulations under the hypothesis of constant thermal conductivity. Our results are validated with experimental measurements finding the best agreement when the ETM is used with a temperature-dependent thermal conductivity

Experimental assessment of anomalous low-frequency noise increase at the onset of Gunn oscillations in InGaAs planar diodes

In this work, the presence of anomalous low-frequency fluctuations during the initiation of higher frequency oscillations in InGaAs-based Gunn planar diodes has been evidenced and investigated. Accurate measurements showing the evolution of the power spectral density of the device with respect to the applied voltage have been carried out. Such spectra have been obtained in the wide frequency range between 10MHz and 43.5 GHz, simultaneously covering both the low-frequency noise and the fundamental oscillation peak at some tens of GHz. This provides valuable information to better understand how these fluctuations appear and how these are distributed in frequency. For much higher frequency operation, such understanding can be utilized as a simple tool to predict the presence of Gunn oscillations without requiring a direct detection

Implementation, efficacy and cost effectiveness of the unified protocol in a blended format for the transdiagnostic treatment of emotional disorders: a study protocol for a multicentre, randomised, superiority controlled trial in the Spanish National Health System

INTRODUCTION Emotional disorders (EDs) have become the most prevalent psychological disorders in the general population, which has boosted the economic burden associated with their management. Approximately half of the individuals do not receive adequate treatment. Consequently, finding solutions to deliver cost-effective treatments for EDs has become a key goal of today’s clinical psychology. Blended treatments, a combination of face-to-face and online interventions, have emerged as a potential solution to the previous. The Unified Protocol for the Transdiagnostic Treatment of EDs (UP) might serve this purpose, as it can be applied to a variety of disorders simultaneously and its manualised format makes it suitable for blended interventions. METHODS AND ANALYSIS The study is a multicentre, randomised, superiority, clinical trial. Participants will be 310 individuals with a diagnosis of an ED. They will be randomised to a treatment as usual (individual cognitive behavioural therapy) or a UP condition in a blended format (face-to-face individual UP +online, app-based UP). Primary outcomes will be ED diagnostic criteria and depression and anxiety symptoms. Cost efficiency of the intervention, app usability, as well as opinion and confidence in the treatment will also be evaluated. Assessment points will include baseline and 3 months, 6 months and 12 months after UP treatment. ETHICS AND DISSEMINATION The study has received approvals by the Ethics Research Committee of Navarra, Castellón, Euskadi, Castilla y León, Extremadura, Lleida and Aragón. The study is currently under an approval process by the Ethics Research Committees of all the remaining collaborating centres. Outcomes will be disseminated through publication in peer-reviewed journals and presentations at international conference meetings.Funding for the study was provided by the PI20/00697 project integrated in Plan Estatal de I+D+I 2017–2020 and co-funded by the 'ISCIII-Subdirección General de Evaluación y Fomento de la investigación del Fondo Europeo de Desarrollo Regional (FEDER), Otra manera de hacer Europa'. Co-funding for this study was also provided by Gobierno de Aragón and FEDER 2014–2020 'Construyendo Europa desde Aragón' (research team: S31_20D). These funding sources had no role in the design of this study and will not have any role during its execution, analyses, interpretation of the data or decision to submit results

Comparative Study of the SEM Evaluation, EDX Assessment, Morphometric Analysis, and Cyclic Fatigue Resistance of Three Novel Brands of NiTi Alloy Endodontic Files

In this study, we compare and analyze the scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), morphometry and cyclic fatigue resistance of Endogal, PathMax, and Smarttrack novel brands of nickel–titanium (NiTi) alloy endodontic files. Material and Methods: Thirty sterile NiTi endodontic rotary files were randomly selected and assigned to one of the following study groups: A: 25.08 F2 Endogal (EDG) (n = 10); B: 25.08 F2 Path Max Pro (PMP) (n = 10); and C: 25.06 Smarttrack (ST) (n = 10). Dynamic cyclic fatigue tests were conducted using a cyclic fatigue device in stainless steel artificial root canal systems with an apical diameter of 250 µm, curvature angle of 60°, radius of curvature of 3 mm, and taper of 6%. Additionally, we analyzed the NiTi endodontic rotary files using EDX, SEM, and morphometry after micro-CT scanning. The results were analyzed using Weibull statistical analysis and ANOVA testing. Results: SEM, EDX, and morphometric analyses showed differences between the three novel brands of NiTi endodontic rotary files. Moreover, statistically significant differences were observed between the number of cycles to failure and time to failure of the three novel brands of NiTi endodontic rotary files (p < 0.001). Conclusions: Smarttrack NiTi alloy endodontic reciprocating files display greater resistance to cyclic fatigue than Endogal and Path Max Pro NiTi alloy endodontic rotary files, due to the reciprocating movement and metallurgical composition