5 Watt GaN HEMT Power Amplifier for LTE

This work presents the design and implementation of a stand-alone linear power amplifier at 2.4 GHz with high output power. A GaN HEMT transistor is selected for the design and implementation of the power amplifier. The device exhibits a gain of 11.7 dB and a drain efficiency of 39% for an output power of 36.7 dBm at 2.4 GHz for an input power of 25dBm. The carrier to intermodulation ratio is better than 25 dB for a two tone input signal of 25 dBm of total power and a spacing of 5 MHz. The fabricated device is also tested with LTE input signals of different bandwidths (5MHz to 20MHz)

A Novel Transparent UWB Antenna for Photovoltaic Solar Panel Integration and RF Energy Harvesting

A novel transparent ultra-wideband antenna for photovoltaic solar-panel integration and RF energy harvesting is proposed in this paper. Since the approval by the Federal Communications Committee (FCC) in 2002, much research has been undertaken on UWB technology, especially for wireless communications. However, in the last decade, UWB has also been proposed as a power harvester. In this paper, a transparent cone-top-tapered slot antenna covering the frequency range from 2.2 to 12.1 GHz is designed and fabricated to provide UWB communications whilst integrated onto solar panels as well as harvest electromagnetic waves from free space and convert them into electrical energy. The antenna when sandwiched between an a-Si solar panel and glass is able to demonstrate a quasi omni-directional pattern that is characteristic of a UWB. The antenna when connected to a 2.55-GHz rectifier is able to produce 18-mV dc in free space and 4.4-mV dc on glass for an input power of 10 dBm at a distance of 5 cm. Although the antenna presented in this paper is a UWB antenna, only an operating range of 2.49 to 2.58 GHz for power scavenging is possible due to the limitation of the narrowband rectifier used for the study

A Flexible 2.45-GHz Power Harvesting Wristband with Net System Output from -24.3 dBm of RF Power

This paper presents a flexible 2.45-GHz wireless power harvesting wristband that generates a net dc output from a -24.3-dBm RF input. This is the lowest reported system sensitivity for systems comprising a rectenna and impedance-matching power management. A complete system has been implemented comprising: a fabric antenna, a rectifier on rigid substrate, a contactless electrical connection between rigid and flexible subsystems, and power electronics impedance matching. Various fabric and flexible materials are electrically characterized at 2.45 GHz using the two-line and the T-resonator methods. Selected materials are used to design an all-textile antenna, which demonstrates a radiation efficiency above 62% on a phantom irrespective of location, and a stable radiation pattern. The rectifier, designed on a rigid substrate, shows a best-in-class efficiency of 33.6% at -20 dBm. A reliable, efficient, and wideband contactless connection between the fabric antenna and the rectifier is created using broadside-coupled microstrip lines, with an insertion loss below 1 dB from 1.8 to over 10 GHz. A self-powered boost converter with a quiescent current of 150 nA matches the rectenna output with a matching efficiency above 95%. The maximum end-to-end efficiency is 28.7% at -7 dBm. The wristband harvester demonstrates net positive energy harvesting from -24.3 dBm, a 7.3-dB improvement on the state of the art.</p

Radio frequency channel characterization for energy harvesting in factory environments

This thesis presents ambient energy data obtained from a measurement campaign carried out at an automobile plant. At the automobile plant, ambient light, ambient temperature and ambient radio frequency were measured during the day time over two days. The measurement results showed that ambient light generated the highest DC power. For plant and operation managers at the automobile plant, the measurement data can be used in system design considerations for future energy harvesting wireless sensor nodes at the plant. In addition, wideband measurements obtained from a machine workshop are presented in this thesis. The power delay profile of the wireless channel was obtained by using a frequency domain channel sounding technique. The measurements were compared with an equivalent ray tracing model in order to validate the suitability of the commercial propagation software used in this work. Furthermore, a novel technique for mathematically recreating the time dispersion created by factory inventory in a radio frequency channel is discussed. As a wireless receiver design parameter, delay spread characterizes the amplitude and phase response of the radio channel. In wireless sensor devices, this becomes paramount, as it determines the complexity of the receiver. In reality, it is sometimes difficult to obtain full detail floor plans of factories for deterministic modelling or carry out spot measurements during building construction. As a result, radio provision may be suboptimal. The method presented in this thesis is based on 3-D fractal geometry. By employing the fractal overlaying algorithm presented, metallic objects can be placed on a floor plan so as to obtain similar radio frequency channel effects. The environment created using the fractal approach was used to estimate the amount of energy a harvesting device can accumulate in a University machine workshop space

Characterization of 28 nm FDSOI MOS and application to the design of a low-power 2.4 GHz LNA

IoT is expected to connect billions of devices all over world in the next years, and in a near future, it is expected to use LR-WPAN in a wide variety of applications. Not all the devices will require of high performance but will require of low power hungry systems since most of them will be powered with a battery. Conventional CMOS technologies cannot cover these needs even scaling it to very small regimes, which appear other problems. Hence, new technologies are emerging to cover the needs of this devices. One promising technology is the UTBB FDSOI, which achieves good performance with very good energy efficiency. This project characterizes this technology to obtain a set of parameters of interest for analog/RF design. Finally, with the help of a low-power design methodology (gm/Id approach), a design of an ULP ULV LNA is performed to check the suitability of this technology for IoT

Development of Textile Antennas for Energy Harvesting

The current socio-economic developments and lifestyle trends indicate an increasing consumption of technological products and processes, powered by emergent concepts, such as Internet of Things (IoT) and smart environments, where everything is connected in a single network. For this reason, wearable technology has been addressed to make the person, mainly through his clothes, able to communicate with and be part of this technological network. Wireless communication systems are made up of several electronic components, which over the years have been miniaturized and made more flexible, such as batteries, sensors, actuators, data processing units, interconnectors and antennas. Turning these systems into wearable systems is a demanding research subject. Specifically, the development of wearable antennas has been challenging, because they are conventionally built on rigid substrates, hindering their integration into the garment. That is why, considering the flexibility and the dielectric properties of textile materials, making antennas in textile materials will allow expanding the interaction of the user with some electronic devices, by interacting through the clothes. The electronic devices may thus become less invasive and more discrete. Textile antennas combine the traditional textile materials with new technologies. They emerge as a potential interface of the human-technology-environment relationship. They are becoming an active part in the wireless communication systems, aiming applications such as tracking and navigation, mobile computing, health monitoring and others. Moreover, wearable antennas have to be thin, lightweight, of easy maintenance, robust, and of low cost for mass production and commercialization. In this way, planar antennas, the microstrip patch type, have been proposed for garment applications, because this type of antenna presents all these characteristics, and are also adaptable to any surface. Such antennas are usually formed by assembling conductive (patch and ground plane) and dielectric (substrate) layers. Furthermore, the microstrip patch antennas, radiate perpendicularly to a ground plane, which shields the antenna radiation, ensuring that the human body is exposed only to a very small fraction of the radiation. To develop this type of antenna, the knowledge of the properties of textile materials is crucial as well as the knowledge of the manufacturing techniques for connecting the layers with glue, seam, adhesive sheets and others. Several properties of the materials influence the behaviour of the antenna. For instance, the bandwidth and the efficiency of a planar antenna are mainly determined by the permittivity and the thickness of the substrate. The use of textiles in wearable antennas requires thus the characterization of their properties. Specific electrical conductive textiles are available on the market and have been successfully used. Ordinary textile fabrics have been used as substrates. In general, textiles present a very low dielectric constant, εr, that reduces the surface wave losses and increases the impedance bandwidth of the antenna. However, textile materials are constantly exchanging water molecules with the surroundings, which affects their electromagnetic properties. In addition, textile fabrics are porous, anisotropic and compressible materials whose thickness and density might change with low pressures. Therefore, it is important to know how these characteristics influence the behaviour of the antenna in order to minimize unwanted effects. To explain some influences of the textile material on the performance of the wearable antennas, this PhD Thesis starts presenting a survey of the key points for the design and development of textile antennas, from the choice of the textile materials to the framing of the antenna. An analysis of the textile materials that have been used is also presented. Further, manufacturing techniques of the textile antennas are described. The accurate characterization of textile materials to use as a dielectric substrate in wearable systems is fundamental. However, little information can be found on the electromagnetic properties of the regular textiles. Woven, knits and nonwovens are inhomogeneous, highly porous, compressible and easily influenced by the environmental hygrometric conditions, making their electromagnetic characterization difficult. Despite there are no standard methods, several authors have been adapting techniques for the dielectric characterization of textiles. This PhD Thesis focuses on the dielectric characterization of the textile materials, surveying the resonant and non-resonant methods that have been proposed to characterize the textile and leather materials. Also, this PhD Thesis summarizes the characterization of textile materials made through these methods, which were validated by testing antennas that performed well. Further a Resonant-Based Experimental Technique is presented. This new method is based on the theory of resonance-perturbation, extracting the permittivity and loss tangent values based on the shifts caused by the introduction of a superstrate on the patch of a microstrip antenna. The results obtained using this method have shown that when positioning the roughest face of the material under test (MUT) in contact with the resonator board, the extracted dielectric constant value is lower than the one extracted with this face positioned upside-down. Based on this observation, superficial properties of textiles were investigated and their influence on the performance of antennas was analysed. Thus, this PhD Thesis relates the results of the dielectric characterization to some structural parameters of textiles, such as surface roughness, superficial and bulk porosities. The results show that both roughness and superficial porosity of the samples influence the measurements, through the positioning of the probes. Further, the influence of the positioning of the dielectric material on the performance of textile microstrip antennas was analysed. For this, twelve prototypes of microstrip patch antennas were developed and tested. The results show that, despite the differences obtained on the characterization when placing the face or reverse-sides of the MUT in contact with the resonator board, the obtained average result of εr is well suited to design antennas ensuring a good performance. According to the European Commission Report in 2009, “Internet of Things — An action plan for Europe”, in the next years, the IoT will be able to improve the quality of life, especially in the health monitoring field. In the Wireless Body Sensor Network (WBSN) context, the integration of textile antennas for energy harvesting into smart clothing is a particularly interesting solution for a continuous wirelessly feed of the devices. Indeed, in the context of wearable devices the replacement of batteries is not easy to practice. A specific goal of this PhD Thesis is thus to describe the concept of the energy harvesting and then presents a survey of textile antennas for RF energy harvesting. Further, a dual-band printed monopole textile antenna for electromagnetic energy harvesting, operating at GSM 900 and DCS 1800 bands, is also proposed. The antenna aims to harvest energy to feed sensor nodes of a wearable health monitoring system. The gains of the antenna are around 1.8 dBi and 2.06 dBi allied with a radiation efficiency of 82% and 77.6% for the lowest and highest frequency bands, respectively. To understand and improve the performance of the proposed printed monopole textile antenna, several manufacturing techniques are tested through preliminary tests, to identify promising techniques and to discard inefficient ones, such as the gluing technique. Then, the influence of several parameters of the manufacturing techniques on the performance of the antenna are analysed, such as the use of steam during lamination, the type of adhesive sheet, the orientation of the conductive elements and others. For this, seven prototypes of the printed monopole textile antenna were manufactured by laminating and embroidering techniques. The measurement of the electrical surface resistance, Rs, has shown that the presence of the adhesive sheet used on the laminating process may reduce the conductivity of the conductive materials. Despite that, when measuring the return loss of printed monopole antennas produced by lamination, the results show the antennas have a good performance. The results also show that the orientation of the conductive fabric does not influence the performance of the antennas. However, when testing embroidered antennas, the results show that the direction and number of the stitches in the embroidery may influence the performance of the antenna and should thus be considered during manufacturing. The textile antennas perform well and their results support and give rise to the new concept of a continuous substrate to improve the integration of textile antennas into clothing, in a more comfortable and pleasure way. A demonstrating prototype, the E-Caption: Smart and Sustainable Coat, is thus presented. In this prototype of smart coat, the printed antenna is fully integrated, as its dielectric is the textile material composing the coat itself. The E-Caption illustrates the innovative concept of textile antennas that can be manipulated as simple emblems. The results obtained testing the antenna before and after its integration into cloth, show that the integration does not affect the behaviour of the antenna. Even on the presence of the human body the antenna is able to cover the proposed resonance frequencies (GSM 900 and DCS 1800 bands) with the radiation pattern still being omnidirectional. At last, the exponential growth in the wearable market boost the industrialization process of manufacturing textile antennas. As this research shows, the patch of the antennas can be easily and efficiently cut, embroidered or screen printed by industrial machines. However, the conception of a good industrial substrate that meets all the mechanical and electromagnetic requirements of textile antennas is still a challenge. Following the continuous substrate concept presented and demonstrated through the E-Caption, a new concept is proposed: the continuous Substrate Integrating the Ground Plane (SIGP). The SIGP is a novel textile material that integrates the dielectric substrate and the conductive ground plane in a single material, eliminating one laminating process. Three SIGP, that are weft knitted spacer fabrics having one conductive face, were developed in partnership with the Borgstena Textile Portugal Lda, creating synergy between research in the academy and industry. The results of testing the performance of the SIGP materials show that the integration of the ground plane on the substrate changes the dielectric constant of the material, as a consequence of varying the thickness. Despite this, after the accurate dielectric and electrical characterization, the SIGP I material has shown a good performance as dielectric substrate of a microstrip patch antenna for RF energy harvesting. This result is very promising for boosting the industrial fabrication of microstrip patch textile antennas and their mass production and dissemination into the IoT network, guiding future developments of smart clothing and wearables.Os atuais desenvolvimentos socioeconómicos e tendências de estilo de vida apontam para um crescimento do consumo de produtos e processos tecnológicos, impulsionado por conceitos emergentes como a Internet das Coisas, onde tudo tudo está conectado em uma única rede. Por esta razão, as tecnologias usáveis (wearable) estão a afirmar-se propondo soluções que tornam o utilizador possivelmente através das suas roupas, capaz de comunicar com e fazer parte desta rede. Os sistemas de comunicações sem fios são constituídos por diversos componentes eletrónicos, que com o passar dos anos foram sendo miniaturizados e fabricados em materiais flexíveis, tais como as baterias, os sensores, as unidades de processamento de dados, as interconexões e as antenas. Tornar os sistemas de comunicações sem fios em sistemas usáveis requer trabalho de investigação exigente. Nomeadamente, o desenvolvimento de antenas usáveis tem sido um desafio, devido às antenas serem tradicionalmente desenvolvidas em substratos rígidos, que dificultam a sua integração no vestuário. Dessa forma, considerando a flexibilidade e as propriedades dielétricas dos materiais têxteis, as antenas têxteis trazem a promessa de permitir a interacção dos utilizadores com os dispositivos eletrónicos através da roupa, tornando os dispositivos menos invasivos e mais discretos. As antenas têxteis combinam os materiais têxteis tradicionais com novas tecnologias e emergem assim como uma potencial interface de fronteira entre seres humanos-tecnologias-ambientes. Expandindo assim a interação entre o utilizador e os dispositivos eletrónicos ao recurso do vestuário. Assim, através das antenas têxteis, o vestuário torna-se uma parte ativa nos sistemas de comunicação sem fios, visando aplicações como rastreamento e navegação, computação móvel, monitorização de saúde, entre outros. Para isto, as antenas para vestir devem ser finas, leves, de fácil manutenção, robustas e de baixo custo para produção em massa e comercialização. Desta forma, as antenas planares do tipo patch microstrip têm sido propostas para aplicações em vestuário, pois apresentam todas estas características e também são adaptáveis a qualquer superfície. Estas antenas são geralmente formadas pela sobreposição de camadas condutoras (elemento radiante e plano de massa) e dielétricas (substrato). Além disso, as antenas patch microstrip irradiam perpendicularmente ao plano de massa, que bloqueia a radiação da antena, garantindo que o corpo humano é exposto apenas a uma fração muito pequena da radiação. Para desenvolver este tipo de antena, é crucial conhecer as propriedades dos materiais têxteis, bem como as técnicas de fabricação para conectar as camadas, com cola, costuras, folhas adesivas, entre outros. Diversas propriedades dos materiais influenciam o comportamento da antena. Por exemplo, a permitividade e a espessura do substrato determinam a largura de banda e a eficiência de uma antena planar. O uso de têxteis em antenas usáveis requer assim uma caracterização precisa das suas propriedades. Os têxteis condutores elétricos são materiais específicos que estão disponíveis comercialmente em diversas formas e têm sido utilizados com sucesso para fabricar o elemento radiante e o plano de massa das antenas. Para fabricar o substrato dielétrico têm sido utilizados materiais têxteis convencionais. Geralmente, os materiais têxteis apresentam uma constante dielétrica (εr) muito baixa, o que reduz as perdas de ondas superficiais e aumenta a largura de banda da antena. No entanto, os materiais têxteis estão constantemente a trocar moléculas de água com o ambiente em que estão inseridos, o que afeta as suas propriedades eletromagnéticas. Além disso, os tecidos e os outros materiais têxteis planares são materiais porosos, anisotrópicos e compressíveis, cuja espessura e densidade variam sob muito baixas pressões. Portanto, é importante saber como estas grandezas e características estruturais influenciam o comportamento da antena, de forma a minimizar os efeitos indesejáveis. Para explicar algumas das influências do material têxtil no desempenho das antenas usáveis, esta Tese de Doutoramento começa por fazer o estado da arte sobre os pontos-chave para o desenvolvimento de antenas têxteis, desde a escolha dos materiais têxteis até ao processo de fabrico da antena. Além disso, a tese identifica e apresenta uma análise dos materiais têxteis e técnicas de fabricação que têm sido utilizados e referidos na literatura. A caracterização rigorosa dos materiais têxteis para usar como substrato dielétrico em sistemas usáveis é fundamental. No entanto, pouca informação existe sobre a caracterização das propriedades eletromagnéticas dos têxteis vulgares. Como já referido, os tecidos, malhas e não-tecidos são materiais heterogéneos, altamente porosos, compressíveis e facilmente influenciados pelas condições higrométricas ambientais, dificultando a sua caracterização eletromagnética. Não havendo nenhum método padrão, vários autores têm vindo a adaptar algumas técnicas para a caracterização dielétrica dos materiais têxteis. Esta Tese de Doutoramento foca a caracterização dielétrica dos materiais têxteis, revendo os métodos ressonantes e não ressonantes que foram propostos para caracterizar os materiais têxteis e o couro. Além disso, esta Tese de Doutoramento resume a caracterização de dieléctricos têxteis feita através dos métodos revistos e que foi validada testando antenas que apresentaram um bom desempenho. No seguimento da revisão, apresenta-se uma Técnica Experimental Baseada em Ressonância. Esta nova técnica baseia-se na teoria da perturbação de ressonância, sendo a permitividade e tangente de perda extraídas com base nas mudanças de frequência causadas pela introdução de um superstrato no elemento radiante de uma antena patch microstrip. Os resultados de caracterização obtidos através deste método revelam que, ao posicionar a face mais rugosa do material em teste em contato com a placa de ressonância, o valor da constante dielétrica extraída é inferior ao valor extraído quando esta face é colocada ao contrário. Com base nesta observação, as propriedades estruturais da superfície dos materiais têxteis foram investigadas e a sua influência no desempenho das antenas foi analisada. Assim, esta Tese de Doutoramento relaciona os resultados da caracterização dielétrica com alguns parâmetros estruturais dos materiais, como rugosidade da superfície, porosidades superficial e total. Os resultados mostram que tanto a rugosidade como a porosidade superficial das amostras influenciam os resultados, que dependem assim do posicionamento do material que está a ser testado. Também foi analisada a influência do posicionamento do material dielétrico na performance das antenas têxteis tipo patch microstrip. Para isso, foram desenvolvidos e testados doze protótipos de antenas patch microstrip. Os resultados mostram que, apesar das diferenças observadas durante o processo de caracterização, o valor médio da permitividade é adequado para a modelação das antenas, garantindo um bom desempenho. De acordo com o relatório da Comissão Europeia, “Internet das Coisas - Um plano de ação para a Europa”, emitido em 2009, nos próximos anos a Internet das Coisas poderá melhorar a qualidade de vida das pessoas, nomeadamente pela monitorização da saúde. No contexto das Redes de Sensores Sem Fios do Corpo Humano, a integração de antenas têxteis para recolha de energia em roupas inteligentes é uma solução particularmente interessante, pois permite uma alimentação sem fios e contínua dos dispositivos. De fato, nos dispositivos usáveis a substituição de baterias não é fácil de praticar. Um dos objetivos específicos desta Tese de Doutoramento é, portanto, descrever o conceito de recolha de energia e apresentar o estado da arte sobre antenas têxteis para recolha de energia proveniente da Rádio Frequência (RF). Nesta tese, é também proposta uma antena impressa do tipo monopolo de dupla banda, fabricada em substrato têxtil, para recolha de energia eletromagnética, operando nas bandas GSM 900 e DCS 1800. A antena visa recolher energia para alimentar os nós de sensores de um sistema usável para monitorização da saúde. Os ganhos da antena apresentada foram cerca de 1.8 dBi e 2.06 dBi, aliados a uma eficiência de radiação de 82% e 77.6% para as faixas de frequência mais baixa e alta, respetivamente. Para entender e melhorar o desempenho da antena impressa tipo monopolo de dupla banda em substrato têxtil, várias técnicas de fabrico foram testadas através de testes preliminares, de forma a identificar as técnicas promissoras e a descartar as ineficientes, como é o caso da técnica de colagem. De seguida, analisou-se a influência de vários parâmetros das técnicas de fabrico sobre o desempenho da antena, como o uso de vapor durante a laminação, o tipo de folha adesiva, a orientação dos elementos irradiantes e outros. Para isto, sete protótipos da antena têxtil monopolar impressa foram fabricados por técnicas de laminação e bordado. As medições da resistência elétrica superficial, Rs, mostrou que a presença da folha adesiva usada no processo de laminagem pode reduzir a condutividade dos materiais condutores. Apesar disso, ao medir o S11 das antenas impressas tipo monopolo produzidas por laminagem, os resultados mostram que as antenas têm uma boa adaptação da impedância. Os resultados também mostram que a orientação do tecido condutor, neste caso um tafetá, não influencia o desempenho das antenas. No entanto, ao testar antenas bordadas, os resultados mostram que a direção e o número de pontos no bordado podem influenciar o desempenho da antena e, portanto, estas são características que devem ser consideradas durante a fabricação. De um modo geral, as antenas têxteis funcionam bem e seus resultados suportam e dão origem ao um novo conceito de substrato contínuo para melhorar a integração de antenas têxteis no vestuário, de maneira mais confortável e elegante. A tese apresenta um protótipo demonstrador deste conceito, o E-Caption: A Smart and Sustainable Coat. Neste protótipo de casaco inteligente, a antena impressa está totalmente integrada, pois o seu substrato dielétrico é o próprio mat

Powering IoT Sensors with RF Energy Harvesting

There is a need to power Internet of Things (IoT) applications that require frequent, expensive, and/or dangerous battery replacements. Radio-frequency energy harvesting (RFEH) is a possible alternative source of power for select IoT sensor applications. In comparison to other methods of energy harvesting, RFEH has the smallest incident power densities and therefore comes with many design challenges. In this project we implement a novel RFEH system powered via a dedicated transmitter. A planar inverted-F antenna (PIFA) and voltage doubler circuit form the designed rectenna (rectifier + antenna) and the system is implemented on a custom PCB to carry out RF-to-DC conversion. The system’s feasibility is demonstrated by powering a commercial power management unit (PMU) and temperature sensor over a test duration of eight hours