Papers by Leonardo Lorenzo Bravo Roger
Esta dissertacao descreve os procedimentos para instalacao, configuracao e utilizacao de uma RSSF... more Esta dissertacao descreve os procedimentos para instalacao, configuracao e utilizacao de uma RSSF em cultivo de Cana-de-Acucar enfatizando o conceito de Agricultura de Precisao. O foco do trabalho foi identificacao das distâncias e posicionamento dos elementos da rede de modo a diminuir o numero de elementos que garantam uma maior cobertura possivel da rede, mantendo um funcionamento adequado nesse tipo de aplicacao. Contudo, possibilita-se uma diminuicao de custo para implantacao e viabilizacao da utilizacao de tecnologia de Redes de Sensores Sem Fio em cultivo da Cana-de-Acucar. O gerenciamento adotado para a Rede de Sensores Sem Fio foi abordagem requisicao e resposta (RR) e modo de energia de Alta Potencia (HP). Foi avaliado experimentalmente que no cultivo de Cana-de-Acucar o desempenho de uma RSSF com topologia estrela na camada sorvedouro e nos sensores e superior a topologia em malha e recomendamos a Topologia Hibrida tambem chamada em Arvore para esse tipo de aplicacao da RSSF. Tambem no importante quesito de consumo de bateria os experimentos mostraram que o modo requisicao resposta em configuracao HP, nao e adequado para tempos na ordem de 2 minutos, deixando aos administradores das redes e aos agricultores deste tipo de cultivo a definicao de um tempo adequado de programacao das requisicoes e respostas nos motes. Abstract
O projeto e a analise teorico-experimental de uma nova etiqueta sem chip para RFID com comunicaca... more O projeto e a analise teorico-experimental de uma nova etiqueta sem chip para RFID com comunicacao redundante e apresentado. Esta nova etiqueta podera ser capaz de operar em duas bandas de frequencias diferentes para a transmissao da informacao binaria, aproveitando a utilizacao em sua concepcao de antenas dual-band. A tecnica aqui mencionada e classica, conhecida como diversidade de frequencia, mas e utilizada neste trabalho pela primeira vez aplicada em etiquetas chipless de RFID visando aumentar a confiabilidade da comunicacao com as leitoras de RFID. Simulacoes realizadas do novo dispositivo proposto com o software HFSS (High Frequency Structural Simulator) mostraram o seu desempenho adequado. A metodologia do projeto e apresentada passo a passo e os resultados sao analisados e discutidos no texto. Abstract
Resumo: O desenvolvimento tecnológico e a necessidade de comunicação entre as pessoas têm aumenta... more Resumo: O desenvolvimento tecnológico e a necessidade de comunicação entre as pessoas têm aumentado o número de dispositivos que se comunicam através de redes sem fio (wireless). A construção de alvenaria, ou seja, paredes feitas de tijolos cerâmicos, blocos de concreto ou folhas planas são algumas das barreiras artificiais podem influenciar a diminuição do sinal de tais redes, torna a comunicação difícil. A indústria da construção tem usado diferentes tipos de resíduos como alternativa para a produção de concreto e argamassa, objetivando minimizar o consumo de material natural e evitar o descarte indevido de resíduos no ambiental. Combinando as necessidades tecnológicas e ambientais, este trabalho tem como objetivo estudar as características da pasta de cimento e resíduos de borracha como a permissividade de ondas de radiofrequência (variação de 2,45 GHz). O objectivo é o de oferecer ao mercado a incorporação deste resíduo para o fabrico de lajes de cimento, de modo que estes podem atenuar as ondas de radiofrequência para a mínimos sem fios.
2017 IEEE International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting, 2017
A compact rectenna using a microstrip patch antenna based on a fractal model and with the rectifi... more A compact rectenna using a microstrip patch antenna based on a fractal model and with the rectifier circuit integrated into the same physical structure has been designed and implemented. The proposed compact rectenna, implemented on a low cost FR-4 substrate, can harverst RF power from 2.4 GHz (ISM band) with a good efficiency (∼48%). The suggested rectenna has been manufactured and experimentally characterized, showing a good agreement with the expected simulated results.
Progress in Electromagnetics Research M, 2018
This paper presents the design of a compact-integrated reconfigurable rectenna array containing 2... more This paper presents the design of a compact-integrated reconfigurable rectenna array containing 2 × 2 compact microstrip patch antennas based on a fractal model with the rectifier circuit integrated into the same physical structure and usable in practical conditions. In this array configuration, four rectennas were mounted in a planar structure with total dimensions of 85 × 85 mm using FR-4 dielectric and with reconfigurable DC output that was tested in three ways: seriesassociation, parallel-association and series-parallel association. In the series-association the rectenna array was able to generate the DC power that reached 6.51 V and maximum efficiency of 64.5%; in the parallel-association it generated the DC power that reached 1.58 V and maximum efficiency of 65.3%; in series-parallel-association it generated the DC power that reached 3.00 V and maximum efficiency of 64.5%. The results showed that rectennas in array configuration are feasible to be used as power supplies to ele...
Wireless communications devices such as mobile phones, tablets, laptops, routers, wireless sensor... more Wireless communications devices such as mobile phones, tablets, laptops, routers, wireless sensor networking modules, etc. that are subject to a dynamic market that increasingly requires miniaturization. One of the strategies followed by technology to respond to this requirement, has been operating on increasingly radio frequencies, but higher the operating frequency, greater the complexity, not only the theoretical project, but especially the assembly of circuit boards of such devices. Expensive and complex robotic machines are used in industry for soldering components on the boards of the radio frequency circuit. This paper shows the step-by-step development of a radiofrequency module for assembly using an inexpensive soldering furnace developed for such. The experience is described in order to disclose a solution that can be useful for carrying out practical projects in university teaching laboratories, unable to acquire professional assembly machines, due to its high cost.
2017 SBMO/IEEE MTT-S International Microwave and Optoelectronics Conference (IMOC), 2017
This work presents the design of a compact antenna using microstrip patch based on a fractal mode... more This work presents the design of a compact antenna using microstrip patch based on a fractal model for use in Internet-of-Things (IoT) wireless communication in sub-GHz bands. The proposed antenna was implemented on a low cost FR-4 substrate and work in the 433 MHz and 915 MHz or 868 MHz frequencies that are ISM bands used in the IoT networks. The suggested antenna has been manufactured and experimentally characterized, showing a good agreement with the expected simulated results.
2021 5th International Symposium on Instrumentation Systems, Circuits and Transducers (INSCIT), 2021
This paper presents an ultra-wideband (UWB) rectenna using discone based antenna and rectifier wi... more This paper presents an ultra-wideband (UWB) rectenna using discone based antenna and rectifier with a high impedance inductor for wireless power transfer. The discone antenna has a well-known wideband frequency coverage and the rectifier using a high impedance inductor removes the matching network requirements and enables the rectenna to operate in ultra-wideband. The UWB rectenna covers the frequency range from 0.65 GHz to 5 GHz and has 16% of efficiency when operating in 2.45 GHz and receiving RF power of 5 dBm. Therefore, the rectenna works on a large frequency range not requiring modifications in order to be used in several applications.
2020 IEEE International Smart Cities Conference (ISC2), 2020
The increase in the number world population of elderly citizens, as well as those who live in sol... more The increase in the number world population of elderly citizens, as well as those who live in solitude, needs an immediate solution with an intelligent monitoring system at home. In this work, we present an intelligent fall-detection system based on IoT to monitor the elderly with your privacy-protected. Currently, fall detection has attracted significant research attention and deep learning has shown promising performance in this task using conventional cameras. However, these traditional methods pose a risk of the leakage of personal privacy. This work proposes a novel fall-detection system that uses a continuous-wave Doppler radar sensor to acquisition the elderly movements and sends this information thought the internet to a server with deep learning using a convolutional neural network (CNN) that identifies the fall. The radar sensor is inexpensive, completely camera-free, and collects no personally identifiable information, thereby allaying privacy concerns. Additionally, unlike traditional cameras, it has environmental robustness and dark/light-independence. The proposed system obtained 99.9% accuracy in detecting falls by using the GoogleNet convolutional neural network. The proposed system is also capable of detecting other types of movements in addition to those tested, including the detection of diseases such as COVID-19 through the cough movement.
Sensors and Actuators A: Physical, 2020
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
XXV Congresso de Iniciação Científica da Unicamp, Oct 21, 2017
Resumo O objetivo dessa pesquisa foi realizar contribuições às leitoras de RFID (Identificação po... more Resumo O objetivo dessa pesquisa foi realizar contribuições às leitoras de RFID (Identificação por Radiofrequência) para os sistemas que utilizam tags sem chip (chipless RFID tags). Uma nova metodologia para a concepção de leitoras utilizando técnicas de Radio Definido por Software (SDR) foi proposta, permitindo conceber uma plataforma multifuncional reconfigurável capaz de se adequar às diferentes situações decorrentes das diversas aplicações
XXV Congresso de Iniciação Científica da Unicamp, Oct 21, 2017
XXV Congresso de Iniciação Científica da Unicamp, Oct 21, 2017
O desenvolvimento de sensores por radiofrequência (RF) está, atualmente, ocupando a atenção dos p... more O desenvolvimento de sensores por radiofrequência (RF) está, atualmente, ocupando a atenção dos pesquisadores. Neste projeto foi feito o estudo do efeito de descasamento que um termístor provoca em uma híbrida de 3dB visando sua utilização como um sensor de temperatura.
SET International Journal of Broadcast Engineering, 2017
Journal of Microwaves, Optoelectronics and Electromagnetic Applications, 2019
In this study are analyzed horn antennas to operating at X band (8-12 GHz) and manufactured by ad... more In this study are analyzed horn antennas to operating at X band (8-12 GHz) and manufactured by additive manufacturing method (AM). To construct the antennas using AM method was necessary made the structure with acrylonitrile butadiene styrene (ABS) thermoplastic using a 3D printer, and then coated the antennas with conductive surfaces. Were fabricated three antennas with different coated techniques: the first antenna with conductive silver paint, the second antenna using copper tape and the third antenna using copper plated. It is investigated the performances of these antennas in terms of the input reflection coefficient, gain, radiation pattern, weight and compared with the conventional aluminum horn antenna with same dimensions.
Revista dos Trabalhos de Iniciação Científica da UNICAMP, 2019
Neste projeto implementou-se um sensor de radiofrequência que opera no domínio do tempo, capaz de... more Neste projeto implementou-se um sensor de radiofrequência que opera no domínio do tempo, capaz de monitorar a umidade do ambiente. O dispositivo implementado apresenta como vantagens o fato de não precisar de bateria nem de nenhum circuito integrado para funcionar. Com isso, pode ser integrado facilmente a uma etiqueta passiva de sistemas de RFID. Seu princípio de funcionamento baseia-se na medição da variação do atraso de grupo introduzido pelo hardware da etiqueta sensora sobre o sinal retro-dispersado pela antena da tag, o que traz mais uma vantagem: a medição pode ser realizada à distância.
Revista dos Trabalhos de Iniciação Científica da UNICAMP, 2019
Este projeto visa a implementação de um sensor de radiofrequência capaz de monitorar a temperatur... more Este projeto visa a implementação de um sensor de radiofrequência capaz de monitorar a temperatura ambiente. O dispositivo a ser implementado não precisa de bateria nem de nenhum circuito integrado para funcionar e pode ser integrado a uma etiqueta passiva de sistemas de RFID. Seu princípio de funcionamento baseia-se na retrodispersão de uma antena, isto traz a vantagem de que a medição pode ser realizada a distância.
IEEE Sensors Journal, 2018
A metamaterial-based microwave sensor with complementary split ring resonator (CSRR) is implement... more A metamaterial-based microwave sensor with complementary split ring resonator (CSRR) is implemented for dielectric characterization of liquids. The novelty in the proposed contactless sensor is the use of liquid samples placed normal to the sensor surface. Placed inside of glass capillary tubes, it is quickly possible to analyze the dielectric properties of liquids simply by replacing the capillary tubes with new samples. The liquid samples inside the glass capillary tubes modify the resonant frequency and Q factor of the CSRR sensor. Thereby a relation between the sensor resonant frequency, Q factor, and complex permittivity of the liquid samples can be estimated. A measurement setup was used to test the proposed sensor that exhibited successfully detection of 10% steps in binary mixtures of ethanol and water. The proposed sensor is compact, low-cost, contactless, reusable, easily fabricated, and easy to work.
IET Microwaves, Antennas & Propagation, 2018
This work presents the design of a rectenna topology by using a compact microstrip patch antenna ... more This work presents the design of a rectenna topology by using a compact microstrip patch antenna based on a fractal model and with the rectifier circuit integrated into the same physical structure. This configuration presents a very reduced circuit area, which makes the proposed rectenna circuit suitable for harvesting and wireless power transfer applications where the size is critical. The proposed compact rectenna, implemented on a low-cost FR-4 substrate, can harvest RF power from 2.45 GHz (ISM band) with a efficiency of ∼62% when the input power harvested by the rectenna is +2 dBm. The suggested rectenna has been manufactured and experimentally characterised, showing a good agreement with the expected simulated results.
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Papers by Leonardo Lorenzo Bravo Roger