Spline-shaped ultra-wideband antenna operating in the ECC released frequency spectrum

A spline-shaped antenna for Ultra-Wideband (UWB) communications that operates in the Electronic Communications Committee (ECC) released band from 6 GHz up to 8.5 GHz is described. Selected simulated and measured data are reported to assess the achieved impedance matching over the whole band of interest, and the distortionless behavior as well as to show the omnidirectional radiation properties. This paper is a postprint of a paper submitted to and accepted for publication in Electronics Letters and is subject to Institution of Engineering and Technology Copyright. The copy of record is available at IET Digital Library

A SVM-Based Multi-Resolution Procedure for the Estimation of the DOAS of Interfering Signals in a Communication System

In this work, the use of a planar antenna system for the estimation of the directions of arrivals (DOAs) of multiple signals impinging on the receiver has been considered. Towards this end, an efficient multi-resolution method based on a SVM-classifier is proposed for determining a probabilitic map of the DOAs of the unknown interfering signals. Numerical results dealing with multiple interferers scenarios in noisy environments are provided in order to assess the feasibility as well as the capability of the proposed approach

On methods to determine bounds on the Q-factor for a given directivity

This paper revisit and extend the interesting case of bounds on the Q-factor for a given directivity for a small antenna of arbitrary shape. A higher directivity in a small antenna is closely connected with a narrow impedance bandwidth. The relation between bandwidth and a desired directivity is still not fully understood, not even for small antennas. Initial investigations in this direction has related the radius of a circumscribing sphere to the directivity, and bounds on the Q-factor has also been derived for a partial directivity in a given direction. In this paper we derive lower bounds on the Q-factor for a total desired directivity for an arbitrarily shaped antenna in a given direction as a convex problem using semi-definite relaxation techniques (SDR). We also show that the relaxed solution is also a solution of the original problem of determining the lower Q-factor bound for a total desired directivity. SDR can also be used to relax a class of other interesting non-convex constraints in antenna optimization such as tuning, losses, front-to-back ratio. We compare two different new methods to determine the lowest Q-factor for arbitrary shaped antennas for a given total directivity. We also compare our results with full EM-simulations of a parasitic element antenna with high directivity.Comment: Correct some minor typos in the previous versio

Convex optimization for the synthesis of matching filters

International audienceIn this work we study a particular filter synthesis problem in order to minimize the reflection coefficient of the global system consisting of filter and antenna. The matching problem is formulated as an optimization problem involving the minimization of a pseudo hyperbolic distance and the solution to this problem using H∞ approach yields a lower bound for the matching criterion related to the computation of a matching filter, with prescribed finite degree, under selectivity constraints

Associação entre prática de atividade física com a saúde mental e a percepção da qualidade de vida em profissionais de enfermagem de Ribeirão Preto e região durante a pandemia da covid-19

Introduction: At the forefront of the COVID-19 pandemic are health professionals who carry out intense work, including nursing professionals, who represent a large number of health professionals working in health and hospital institutions. The high pressures in the work environment with expended workloads and journeys increased the demands due to the responsibility of their attributions. This context can negatively affect these professionals’ physical activity practices, mental health, and perceived quality of life. Objective: Analyze the association between physical activity practice, mental health, and perceived quality of life in nursing professionals from Ribeirao Preto, SP, during the COVID-19 pandemic. Methods: This cross-sectional study was performed with nursing professionals from the Ribeirao Preto and region area in 2021 through an online form on the Google Forms tool. Questions related to sociodemographic data, professional activity, questionnaires to measure physical activity levels and sedentary behavior (IPAQ - short version), quality of life perception (SF - 12v2), and mental health (DASS-21) were used. Regarding the statistical analysis, the Chi-square test was used to verify the association of two categorical variables; the Student’s T-test to compare two means, and the ANOVA to compare three means from unpaired samples. The significance level was 5%. Results: 125 professionals participated in the study, such as assistants, technicians, nurses, and coordinating nurses. Among them, 79.2% were women, 56.0% worked in the private sector, 34.4% were overweight, and 29.6% were obese. Professionals who practiced physical exercise or sport had a lower risk of depression (57.9% among non-practicing professionals, 47.9% among practicing one type of exercise, and 18.2%among practicing two or more types of exercise or sports, p = 0.04). In addition, professionals with moderate or high physical activity levels and who practiced physical exercises or sports had a better score in multiple domains and physical and mental quality of life components compared with low physical activity levels and not practicing physical exercises or sports, respectively. Conclusion: Nursing professionals who reported practicing more physical exercises or sports had lower mental health-related risks, and those who reported moderate or high physical activity levels had a better perception of quality of life.Introdução: Na linha de frente da pandemia da COVID-19 encontram-se os profissionais de saúde que realizam um intenso trabalho, incluindo os profissionais de enfermagem, que representam uma grande parcela entre os profissionais de saúde que atuam nas instituições de saúde e hospitalares. As altas pressões no ambiente de trabalho com elevadas cargas e jornadas aumentaram as demandas, devido à responsabilidade de suas atribuições. Este contexto pode trazer repercussões negativas para a prática da atividade física, saúde mental e percepção de qualidade de vida destes profissionais. Objetivo: Analisar a associação entre a prática de atividade física, saúde mental e a percepção da qualidade de vida em profissionais de enfermagem de Ribeirão Preto, SP durante a pandemia da COVID-19. Métodos: Trata-se de um estudo transversal realizado com profissionais de enfermagem de Ribeirão Preto e região em 2021, por meio de formulário online na ferramenta Google Forms. Foram realizadas perguntas relacionadas aos dados sociodemográficos, atividade profissional, questionários para medir nível de atividade física e comportamento sedentário (IPAQ – versão curta), percepção da qualidade de vida (SF – 12v2) e saúde mental (DASS-21). Sobre a análise estatística, utilizou-se o teste Qui-quadrado para verificar a associação de duas variáveis categóricas entre si; teste t de Student para comparar duas médias e a ANOVA para comparar três médias provenientes de amostras não pareadas. O nível de significância foi de 5%. Resultados: Participaram do estudo 125 profissionais de enfermagem, sendo auxiliares, técnicos, enfermeiros(as) e enfermeiros(as) coordenadores(as). Desses, 79,2% foram mulheres e 56% atuavam no setor privado, 34,4% estavam acima do peso e 29,6% com obesidade. Os profissionais que praticavam exercício físico ou esporte apresentaram menor risco de depressão (57,9% entre os que não praticavam, 47,9% entre os que praticavam um tipo e 18,2% entre os que praticavam dois ou mais tipos de exercício ou esporte, p = 0,04). Profissionais com moderado ou alto nível de atividade física e que praticavam exercícios físicos ou esportes, apresentaram melhor pontuação em diversos domínios e nos componentes físico e mental da qualidade de vida, quando comparados aos com baixo nível de atividade física e que não praticavam exercícios físicos ou esportes, respectivamente. Conclusão: Profissionais de enfermagem que relataram praticar mais exercícios físicos ou esporte apresentaram menor risco relacionado à saúde mental, e os que relataram nível moderado ou alto de atividade física apresentaram melhor percepção de qualidade de vida

A multifunctional compact pattern reconfigurable antenna with Four radiation patterns for sub-GHz IoT applications

ABSTRACT: A compact pattern reconfigurable antenna with four radiation patterns is proposed for sub-GHz IoT applications. The antenna has two functional modes; Mode I has three uncorrelated patterns, while Mode II has electric and magnetic omnidirectional patterns. The resonant frequency of the antenna is 868 MHz with measured overlapped −6 dB impedance-bandwidths of 22 MHz and 20 MHz for Mode I and Mode II, respectively. The antenna is integrated in an 80×55 mm2 terminal. The radiating elements consist of two meandered slots and one meandered monopole. Four pattern configurations are obtained with an average peak gain of 0 dBi, and an average radiation efficiency of 43.3%. Two of the patterns are with 5 dB directivity, and the other two are omnidirectional patterns. Pattern reconfigurability is achieved using four PIN diodes. The antenna is fabricated on a low-cost FR-4 substrate. By removing FR-4 material inside the slots, slots’ radiation efficiencies were improved by 2.25 dB

Evaluating Smartphone Accuracy for LTE Power Measurement

Smartphones are today relatively cheap devices that embed a large variety of sensors such as magnetometers or orientation sensors, but also the hardware to connect to most wireless communication technologies such as Wi-Fi, Bluetooth, or cellular networks. For this reason, companies, such as OpenSignal or Tutela use smartphones to make crowd-based measurements of the received power from the cellular infrastructure to help operators manage their infrastructure. However, to the best of our knowledge, the accuracy of such measurements has never been rigorously assessed. The goal of this paper is to assess how accurate are measurements of received power from a 4G (LTE) antenna when performed from a Commercial Off-The-Shelf~(COTS) smartphone in different environments. We first evaluate the granularity and limitations of the Android API that returns the received power. We explore how reliable are the measurements from a mono-polarized antenna in a fully controlled environment. We show that the orientation of the smartphone, the position of the source, and the distance to the source has a significant impact on the accuracy of the measurements. We introduce several calibration techniques based on radiation matrices manipulations and machine learning to calibrate the measurements, that is, to improve the accuracy to less than 5 dBm RMSE compared to a professional equipment. Finally, we explore how reliable are measurements in an outdoor environment, in the context of a multi-polarized antenna

Open-Source 4G Experimental Setup (Report)

In this work, we show how to set up a cellular LTE network for wireless experimentation and measurement, relying on commodity hardware and open-source software. We first deploy a complete LTE network on a single laptop and an SDR hardware. Then, we use it to evaluate the reception performance of a commercial smartphone. In the end, we propose a calibration technique which allows using a smartphone as a wireless power measurement tool by reducing the root-mean-square error of the RSSI, with respect to a reference power measured with a specialized spectrum analyzer, from 6.4 dBm to 2.4 dBm

Evaluating Smartphone Accuracy for RSSI Measurements

International audienceSmartphones are today affordable devices, capable of embedding a large variety of sensors such as magnetometers or orientation sensors, but also the hardware needed to connect them to most wireless communication technologies such as Wi-Fi, Bluetooth, or cellular networks. Therefore, they are handy devices able to perform Received Signal Strength Indicator (RSSI) measurements for a wide variety of applications such as cellular coverage maps, indoor localization, or proximity tracking. However, to the best of our knowledge, the accuracy of such measurements has never been rigorously assessed. The goal of this paper is to assess the accuracy of the RSSI measurements made with a Commercial Off-The-Shelf (COTS) smartphone in a variety of conditions, and how possible inaccuracies can be corrected. We primarily focus on the LTE RSSI, but we also extend our results to the Bluetooth RSSI. In this paper, we build a controlled experimental setup based on commodity hardware and on open-source software. We evaluate the granularity and limitations of the Android API that returns the RSSI. We explore how reliable the measurements in a controlled environment with a monopolarized antenna are. We show that the orientation of the smartphone, the position or orientation of the source, and the transmission power have a significant impact on the accuracy of the measurements. We introduce several correction techniques based on radiation matrix manipulations and on machine learning in order to improve measurement accuracy to less than 5 dBm RMSE, as compared to a professional equipment. We also explore the reliability of measurements made in an outdoor realistic environment. We show that whereas transmission diversity available in LTE base stations significantly improves the measured RSSI regardless of the smartphone orientation, the Bluetooth RSSI remains largely sensitive to the smartphone orientation