100 research outputs found

    Basic Antenna Theory and Application

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    Currently highly directive antennas on the market can range from as little as fifty dollars to a couple of hundreds of dollars. The gain of these antennas is between the ranges between 8dBi to 20dBi. A cheaper alternative with a similar gain characteristic can be developed to appeal to the consumers on the market. This project involves the designing, building, and testing of a highly directional antenna that can be manufactured cheaply and be sold at a price that would be appeal to customers

    Bounding the Practical Error of Path Loss Models

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    We seek to provide practical lower bounds on the prediction accuracy of path loss models. We describe and implement 30 propagation models of varying popularity that have been proposed over the last 70 years. Our analysis is performed using a large corpus of measurements collected on production networks operating in the 2.4 GHz ISM, 5.8 GHz UNII, and 900 MHz ISM bands in a diverse set of rural and urban environments. We find that the landscape of path loss models is precarious: typical best-case performance accuracy of these models is on the order of 12–15 dB root mean square error (RMSE) and in practice it can be much worse. Models that can be tuned with measurements and explicit data fitting approaches enable a reduction in RMSE to 8-9 dB. These bounds on modeling error appear to be relatively constant, even in differing environments and at differing frequencies. Based on our findings, we recommend the use of a few well-accepted and well-performing standard models in scenarios where a priori predictions are needed and argue for the use of well-validated, measurement-driven methods whenever possible

    MIMO antenna systems for next generation wireless communications

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    Multiple Input Multiple Output wireless communications systems require as the name implies multiple antennas at the transmit and receive side of a link, as all multiple elements operationally occupy the same spectrum, the capacity of carrying information is increased with no increase in the transmission bandwidth or power. Antennas destined for MIMO systems need to address the issue of adequate isolation between elements and the issue of the diversity performance of the array, these issues become challenging for mobile terminals. In this thesis dual band arrays for the mobile and the access point are proposed along with dual band mutual coupling reduction and radiation pattern improvement methods. First a dual band two element printed inverted F stacked monopole array is proposed for the mobile terminal. The single elements in the array are easily tuneable and achieve impedance matching from an open stub. The configuration is compact, with radiators distanced at 0.13λ0. By use of a grid of parasitically coupled printed lines mutual coupling is reduced by 9dB, where at the lower band at 2.4GHz, S12 = −18dB. Then a dual band two element printed dipole array is proposed for a pico–micro cell access point. The dipoles are fed by a printed balun which provides wide impedance bandwidth at two bands. To improve the radiation pattern at both frequencies the array is positioned above a dual band frequency selective surface, acting as an artificial magnetic conductor, thus allowing the screen to be placed 0.03λ0 from the array while maintaining good radiation efficiency. Finally a brief discussion of dual band surface wave suppression for printed antennas is presented. Here it is suggested that the surface waves can be eliminated by a superstrate at one band and by an EBG lattice at the second band. Initial experiments with different size superstrates and three periods of mushroom type EBG, show that mutual coupling can be reduced and the radiation pattern can be modified.EThOS - Electronic Theses Online ServiceEngineering and Physical Sciences Research Council (EPSRC)GBUnited Kingdo

    Agregados 2D de antenas microstrip não uniformes para aplicações sem fios

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    Doutoramento em Engenharia ElectrotécnicaWireless communications have undergone over the last decades a tremendous progress as a consequence of the exponential growth in demand for mobile devices, and nowadays are more and more involved in people's lives. This presence is re ected through the use of a large number of applications of which they become increasingly dependent on. The antenna, in its most di erent forms, are crucial elements in the establishment this type of communication. Each application involves a number of speci c characteristics, whereby, the improvement of wireless communications is related to the appropriateness of the used antenna. Many applications require antennas with radiation pattern with its particular shapes (in terms of beamwidth, side lobes levels, direction, etc ..), static or dynamic (adaptive antennas), involving in most cases the use antenna arrays to meet to such constraints. In this thesis, a number of techniques to synthesize antennas consisting of planar arrays with nonuniform excitation of their elements, are addressed. A group of the direction of arrival and beamforming estimation algorithms are also presented and analyzed, in order to enable their application in adaptive antenna array with dynamic beamforming. A vast and diversi ed set of arrays with di erent radiation requirements, and for di erent applications were developed. These arrays have great applicability in current research topics in antennas, such as vehicle communications, Wi-Fi in sports venues and smart antennas.As comunicações sem os têm sofrido, ao longo das ultimas décadas, um enorme progresso em consequência do aumento exponencial da procura de dispositivos móveis, estando hoje em dia cada vez mais presentes na vida das pessoas. Esta presença re ete-se através do uso de um elevado número de aplicações das quais se tornam cada vez mais dependentes. As antenas, nas suas mais diversi cadas formas, são elementos cruciais no estabelecimento deste tipo de comunicações. Cada aplicação envolve um conjunto de características especí cas, pelo que a melhoria das comunica ções sem os está relacionada com a adequação da antena usada. Muitas aplicações necessitam de antenas com diagramas de radiação com formatos próprios (em termos de larguras de feixe, níveis de lobos secund ários, direção, etc..), sejam eles estáticos ou dinâmicos (antenas adaptativas), implicando na maioria dos casos o uso de agregados de antenas para fazer face a tais condições. Nesta tese são abordadas várias técnicas de desenho de antenas constituídas por agregados planares, com alimentação não uniforme dos seus elementos. Um conjunto de algoritmos de estimação dos ângulos de chegada e de formação de feixe são também apresentados e analisados com vista à sua aplicação em agregados de antenas adaptativas, com formação de feixe dinâmico. Um vasto e diversi cado conjunto de agregados com diferentes requisitos de radiação, destinados a diferentes aplicações foram desenvolvidos. Estes agregados têm grande aplicabilidade nos atuais tópicos de investiga ção em antenas, tais como as comunicações veiculares, Wi-Fi em espaços desportivos e smart antenas

    Produção de satélites de baixo custo

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    mstrado em Engenharia Eletrónica e TelecomunicaçõesA necessidade por uma conectividade contínua, seja por motivos pessoais ou profissionais, está a levar ao congestionamento global das redes terrestres. O espaço e os seus respetivos satélites, são agora, mais do que nunca, uma solução à qual recorrer e as grandes empresas já começaram a re-fazer esse link, chamando-lhe Internet do Espaço. Esta dissertação surge com o propósito de desenvolver um micro satélite de muito baixo custo para uma aplicação de Internet das Coisas, utilizando tecnologia LoRa. O objetivo principal deste trabalho é provar o conceito de que uma nova era de "toaster-size satellites" é agora possível. Esta temática requer conhecimento teórico de conceitos como antenas, tecnologia LoRa e LoRaWAN, assim como eletrónica. Um pequeno protótipo deste micro satélite foi construído com base em tecnologia LoRaWAN, com a implementação de uma gateway LoRaWAN e o desenho de um não com muito baixo consumo. De todos os aspetos relacionados com a Internet do Espaço, este trabalho visa o seu foco em antenas e na performance do sistema total.The need for continuous connectivity, either for personal or professional purposes, is building a path to a global congestion of terrestrial networks. The space and its satellites are now, more than ever, a solution to go to and big companies have already started to reshape this link, calling it Internet of Space. This dissertation arises with the purpose of developing a super low-cost micro satellite for an Internet of Things network, using LoRa technology. The main goal of this work is to prove the concept that a new era of "toaster-size satellites" is now possible. This thematic requires theoretical knowledge of concepts like antennas, LoRa and LoRaWAN technologies, as well as electronics. A small prototype of this micro satellite network was built based on LoRaWAN technology, with the implementation of a LoRaWAN gateway, and the design of a super low-power end device. Besides all the possible aspects related to IoS, this work aims to focus on the antennas, and on the performance of the assembled system

    Comparative study of increasing indoor WLAN coverage by passive repeating systems

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    Abstract. Propagation of radio waves is interrupted while traveling through different materials. The architectural beautification and complexity by using various building materials cause attenuation of the signal via indoor, outdoor to indoor and vice versa wireless communications. It has been found that feeding more power to the transmitter or increasing sensitivity of the receiver is one of the solutions to overcome weak connectivity. However, this approach is not cost effective. Another concern is the ability to amplify the wireless signal, especially in WLAN operation. WLAN is one of the most popular ways of establishing a wireless communication network to connect our daily used devices such as mobile phone, laptop, IP camera etc. Path loss, attenuation by materials and the delivered power from the transceiver are the variables to determine the efficiency of this communication network. A passive repeating method has been discussed in this thesis which addresses the mentioned concerns. It is cost effective and in a case of power consumption, does not need any energy outside the system. On the other hand, there are few maintenance costs, if any, for this kind of system. To achieve this, a back-to-back antenna approach has been tested in this study. In a back-to-back system, two antennas are connected by a short waveguide connection to decrease attenuation e.g. a wall. The main challenge concerning the effectiveness of this method was to design and fabricate efficient antennas, which are connected with a coaxial cable. There are multiple frequency bands available for WLAN communication. In this thesis, a frequency of 2.43 GHz is considered. Computer simulation of antennas, fabrication, individual measurement and full passive repeating system measurement has been presented. A prototype of a circular patch antenna is built with a 4.63 dB gain and a return loss of 15.18 dB. The passive repeating system is built by using a commercially available dipole antenna at the other end of the coaxial cable. In various cases, there was an observable improvement of the signal of between 2 dB to 6 dB. Required background and theoretical studies are presented along with the output of the simulated and measured prototype comparison. It is clear from this study that the passive repeating system can be used in some specific indoor areas. Keywords: WLAN, passive repeater, path loss, attenuation, indoor communication

    Optically Transparent Antennas and Filters for Smart City Communication

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    Incremental usage of mobile devices demand a new generation of wireless networks (5G) to provide faster data rates, more reliable coverage, monitor city infrastructure usage, and increase network capacity. The frequencies proposed for the upcoming 5G network would result in shorter broadcast distances and network dead zones, countered by incorporating transparent antennas into glass high rises. Transparent antennas possess, however a major challenge: low gain. This lower gain can be countered by means of employing antennas in an antenna array, boosting the gain and even giving the array the ability to beam form for the upcoming 5G network. The 5G dead zones can be countered with strategically placed transparent reflectors embedded into the glass surfaces of city high-rises. This dissertation shows there are significant effects due to the transparent antennas’ carrier concentration and film thickness. Changes in film conductivity and thicknesses results in shifts for filter and antenna resonances. A 4x1 GZO antenna array was constructed to operate at 5.8 GHz, and the results show approximately 10dBi of lower aperture gain between a copper version of the array and the GZO version of the array. However, the 4x1 GZO array shows an approximate 12dBi increase in gain over a single GZO antenna element. The technology developed in this dissertation has a broader impact other than for smart cities and the upcoming 5G network. Transparent antenna arrays offer sight insensitive military communication systems and eye-worn medical and commercial devices to monitor eye health and other various health signs

    Automated design optimisation and simulation of stitched antennas for textile devices

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    This thesis describes a novel approach for designing 7-segment and 5-angle pocket and collar planar antennas (for operation at 900 MHz). The motivation for this work originates from the problem of security of children in rural Nigeria where there is risk of abduction. There is a strong potential benefit to be gained from hidden wireless tracking devices (and hence antennas) that can protect their security. An evolutionary method based on a genetic algorithm was used in conjunction with electromagnetic simulation. This method determines the segment length and angle between segments through several generations. The simulation of the antenna was implemented using heuristic crossover with non-uniform mutation. Antennas obtained from the algorithm were fabricated and measured to validate the proposed method.This first part of this research has been limited to linear wire antennas because of the wide range and flexibility of this class of antennas. Linear wire antennas are used for the design of high or low gain, broad or narrow band antennas. Wire antennas are easy and inexpensive to build. All the optimised linear wire antenna samples exhibit similar performances, most of the power is radiated within the GSM900 frequency band. The reflection coefficient (S11) is generally better than -10dB. The method of moment (MoM-NEC2) and FIT (CST Studio Suite 2015) solvers were used for this design. MATLAB is used to as an interface to control computational electromagnetic solvers for antenna designs and analysis. The genetic algorithm procedures were written in MATLAB. The second part of the work focuses on meshed ground planes for applications at 900 MHz global system for mobile communications (GSM), 2.45 GHz industrial, scientific, and medical (ISM) band and 5 GHz wearable wireless local area networks (WLAN) frequencies. Square ground planes were developed and designed using linear equations in MATLAB. The ground plane was stitched using embroidery machines. To examine the effect of meshing on the antenna performance and to normalise the meshed antenna to a reference, solid patch antenna was designed, fabricated on an FR4 substrate. A finite grid of resistors was created for numerical simulation in MATLAB. The resistance from the centre to any node of a finite grid of resistors are evaluated using nodal analysis. The probability that a node connects to each node in the grid was computed. The circuit model has been validated against the experimental model by measurement of the meshed ground plane. A set of measurement were collected from a meshed and compared with the numerical values, they show good agreement.</div

    Reconfigurable Antenna Systems: Platform implementation and low-power matters

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    Antennas are a necessary and often critical component of all wireless systems, of which they share the ever-increasing complexity and the challenges of present and emerging trends. 5G, massive low-orbit satellite architectures (e.g. OneWeb), industry 4.0, Internet of Things (IoT), satcom on-the-move, Advanced Driver Assistance Systems (ADAS) and Autonomous Vehicles, all call for highly flexible systems, and antenna reconfigurability is an enabling part of these advances. The terminal segment is particularly crucial in this sense, encompassing both very compact antennas or low-profile antennas, all with various adaptability/reconfigurability requirements. This thesis work has dealt with hardware implementation issues of Radio Frequency (RF) antenna reconfigurability, and in particular with low-power General Purpose Platforms (GPP); the work has encompassed Software Defined Radio (SDR) implementation, as well as embedded low-power platforms (in particular on STM32 Nucleo family of micro-controller). The hardware-software platform work has been complemented with design and fabrication of reconfigurable antennas in standard technology, and the resulting systems tested. The selected antenna technology was antenna array with continuously steerable beam, controlled by voltage-driven phase shifting circuits. Applications included notably Wireless Sensor Network (WSN) deployed in the Italian scientific mission in Antarctica, in a traffic-monitoring case study (EU H2020 project), and into an innovative Global Navigation Satellite Systems (GNSS) antenna concept (patent application submitted). The SDR implementation focused on a low-cost and low-power Software-defined radio open-source platform with IEEE 802.11 a/g/p wireless communication capability. In a second embodiment, the flexibility of the SDR paradigm has been traded off to avoid the power consumption associated to the relevant operating system. Application field of reconfigurable antenna is, however, not limited to a better management of the energy consumption. The analysis has also been extended to satellites positioning application. A novel beamforming method has presented demonstrating improvements in the quality of signals received from satellites. Regarding those who deal with positioning algorithms, this advancement help improving precision on the estimated position

    Near Field Coupling in Wireless Systems for Identification, Sensing and Communication

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    Antennas for radio communication systems (e.g. radio links, cellular networks, WLAN, remote sensing) are designed giving a lot of attention to antenna gain, polarization, radiation pattern characteristics (e.g. half power beam width, front to back ratio, etc.). All above parameters are defined in the antenna far-field (FF) region, so they are suitable to characterize a communication system in which the transmitter and the receiver antennas are far enough. On the other hand, some applications exist that exploit antenna features in its near-field (NF) region. In this context, NF coupling between antennas has been studied since a long time and most researches have been focused on coupling effects in antenna arrays, field sensing for near-field antenna scanning systems, magnetic coupling between loops operating at LF-HF frequency bands. During his PhD course, the author designed and tested several antennas for Near-Field applications such as UHF RFID Desktop Reader. Moreover, he developed numerical codes to analyze a novel method to estimate the deep human tissues status with a near-field sensor, determining its prediction capability and determining critical parameters that affect its accuracy. Finally, he studied the mutual coupling effect between antennas integrated in commercial PV panels for wireless communication systems
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