Tesis sobre el tema "Electromagnetic ground waves. Radio"

Thesis (M.S)--West Virginia University, 2007.
Title from document title page. Document formatted into pages; contains xi, 104 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 69-70).

Thesis (Ph. D.)--Missouri University of Science and Technology, 2009.
Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed November 23, 2009) Includes bibliographical references.

Thesis (M.S. in Meteorology)--Naval Postgraduate School, March 2010.
Thesis Advisor(s): Guest, Peter S. ; Goroch, Andreas K. "March 2010." Author(s) subject terms: Electromagnetic propagation, electromagnetic scattering, groundwave propagation, mathematical techniques, variance reduction. Includes bibliographical references (p. 67-68). Also available in print.

The dominant natural electromagnetic (EM) radiation in the extremely low frequency (ELF) range is due to global lightning activity. Radio waves of ELF band traveling along the surface of the ground are able to circle the globe and return to the starting point. Schumann Resonances (SR) are the EM phenomena which occur in the cavity formed by the conducting Earth and the ionosphere, with peak frequencies close to 8, 14, 20, 26 Hz, etc. The spectral characteristics of the SR modes are defined by their resonant mode amplitudes, center frequencies and half-widths. The characteristics of the SR became important in aerospace, marine applications, atmospheric studies, in addition to their relevance to global lightning studies due to their frequency band. The objective of this work is two fold: (i) to investigate the characteristics of SR parameters obtained at Sarkoy in Turkey
(ii) to model the nonlinear characteristics of the Near Earth Space Processes by forecasting the 1st SR mode intensities different time steps in advance using neural network modeling approach. The results show that the SR amplitudes exhibit the characteristics of Tropical African lightning activity and have maxima around 1400 UT. The neural network results show that the proposed model is able to forecast SR amplitudes from 0,5 to 36 hours in advance within reasonable error limits. Furthermore, a fuzzy neural network model with a non&ndash
linear optimization algorithm for the training phase is proposed and tested for the future work.

The modulated scattering technique is used in conjunction with a Software Defined Radio (SDR) dongle to obtain a software-based modulated signal output. SDR# is the software package used to get spectrum analysis of the modulated signal. A transmitter yagi antenna sends a 2.304GHz signal on to an antenna connected to a reflector coefficient modulator (700Hz) and the modulated waves are received by another yagi. The receiver yagi antenna is then connected to a frequency converter to convert a 2.304GHz signal to a 144MHz dongle input signal which finally puts the scattered output on computer software with a SDR dongle. The output has a center frequency with modulated spectral lines on either side of the measured frequency. Finally, antenna patterns are measured with different types of antennas by rotating the antennas and observing the baseband modulation sidebands.

Modern communication systems rely heavily upon microwave, radio, and other electromagnetic frequency bands as a means of providing wireless communication links. Although convenient, wireless communication is susceptible to electromagnetic interference. Solar activity causes both direct interference through electromagnetic radiation as well as indirect interference caused by charged particles interacting with Earth's magnetic field. The Solar Radio Burst Locator (SRBL) is a United States Air Force radio telescope designed to detect and locate solar microwave bursts as they occur on the Sun. By analyzing these events, the Air Force hopes to gain a better understanding of the root causes of solar interference and improve interference forecasts. This thesis presents methods of searching and analyzing events found in the previously unstudied SRBL data archive. A new web-based application aids in the searching and visualization of the data. Comparative analysis is performed amongst data collected by SRBL and several other instruments. This thesis also analyzes events across the time, intensity, and frequency domains. These analysis methods can be used to aid in the detection and understanding of solar events so as to provide improved forecasts of solar-induced electromagnetic interference.

Radars are used for range estimation of distant objects. They operate on the principle of sending electromagnetic pulses that are reflected off a target. This leads to the propagation of electromagnetic waves over large distances. As the waves propagate, they are affected by several aspects that decrease the performance of the radar system. In this master thesis, we derive a mathematical model that describes electromagnetic propagation in the troposphere. The model developed is based on a parabolic equation and uses the split-step Fourier method for its numerical solution. Using the model, we estimate the influence of a varying, complex, refractive index of the atmosphere, different lossy materials in the ground, terrain, and oceans. The terrain is described using a piecewise linear shift map method. The modelling of the ocean is done using a novel model which is a combination of terrain for large swells and Miller surface roughness for smaller waves, both based on a Pierson-Moskowitz sea spectrum. The model is validated and found to agree very well, with results found in the literature.

Radio magnetotellurics (RMT), crosshole ground penetrating radar (GPR), and crosshole electrical resistance tomography (ERT) were applied in a range of hydrogeological applications where geophysical data could improve hydrogeological characterization. A profile of RMT data collected over highly resistive granite was used to map subhorizontal fracture zones below 300m depth, as well as a steeply dipping fracture zone, which was also observed on a coinciding seismic reflection profile. One-dimensional inverse modelling and 3D forward modelling with displacement currents included were necessary to test the reliability of features found in the 2D models, where the forward models did not include displacement currents and only lower frequencies were considered. An inversion code for RMT data was developed and applied to RMT data with azimuthal electrical anisotropy signature collected over a limestone formation. The results indicated that RMT is a faster and more reliable technique for studying electrical anisotropy than are azimuthal resistivity surveys. A new sequential inversion method to estimate hydraulic conductivity fields using crosshole GPR and tracer test data was applied to 2D synthetic examples. Given careful surveying, the results indicated that regularization of hydrogeological inverse problems using geophysical tomograms might improve models of hydraulic conductivity. A method to regularize geophysical inverse problems using geostatistical models was developed and applied to crosshole ERT and GPR data collected in unsaturated sandstone. The resulting models were geologically more reasonable than models where the regularization was based on traditional smoothness constraints. Electromagnetic geophysical techniques provide an inexpensive data source in estimating qualitative hydrogeological models, but hydrogeological data must be incorporated to make quantitative estimation of hydrogeological systems feasible.

The use of mobile communication devices (e.g. mobile phones, tablets, and laptops) increased during the last few years, especially in preadolescents and adolescents. In order to function, mobile communication devices require a constant exchange of information achieved using radiofrequency electromagnetic fields (RF-EMF). Evidence is limited for potential effects of RF-EMF exposure to the brain and epidemiological studies that assessed RF-EMF exposure and its relationship with sleep and neurodevelopment are scarce. This thesis aimed to better understand the potential association between RF-EMF exposure and sleep, and RF-EMF exposure and neurodevelopment by: i) using a comprehensive RF-EMF exposure assessment (i.e. distinguish between sources with different patterns of RF-EMF exposure to the brain such as phone calls, screen activities, and environmental sources, ii) estimating the amount of RF-EMF the brain absorbs from each source and overall, ii) assessing sleep using objective measures collected with actigraphy, and iii) assessing neurodevelopment as cognitive function and brain volumes. The use of some mobile communication devices such as the tablet and problematic mobile phone use were associated with poorer sleep quality and less favourable objective sleep measures. Moreover, evening whole-brain RF-EMF dose from phone calls was associated with less favourable objective sleep measures. Regarding neurodevelopment, overall whole-brain RF-EMF dose and whole-brain RF-EMF dose from phone calls were not associated with brain volumes but whole-brain RF-EMF dose from screen activities was associated with smaller caudate volume. Finally, overall whole-brain RF-EMF dose and whole-brain RF-EMF dose from phone calls was associated with non-verbal intelligence. Given that the biological mechanism behind the observed associations between RF-EMF exposure and sleep, and RF-EMF exposure and neurodevelopment is unknown, that we found small effects sizes, and that we could not entirely disentangle between minutes of use and RF-EMF dose, our results should be interpreted with caution. We cannot discard chance finding, reverse causality, or that other non-RF-EMF factors related to the use of mobile communication devices are behind the observed associations (e.g. blue light, addiction, mental arousal or sleep displacement).
El uso de dispositivos móviles de comunicación como los teléfonos móviles, tabletas y ordenadores portátiles ha aumentado en los últimos años, especialmente en preadolescentes y adolescentes. Los dispositivos móviles de comunicación utilizan los campos electromagnéticos de radiofrecuencia (CEM-RF) para el intercambio constante de información necesario para su funcionamiento. La evidencia científica de los efectos que tiene la exposición a CEM-RF al cerebro es limitada y los estudios epidemiológicos que evalúan la exposición de CEM-RF y su relación con el sueño y el neurodesarrollo son escasos. Esta tesis tiene como objetivo entender mejor las asociaciones entre la exposición a CEM-RF y el sueño y la exposición a CEM-RF y el neurodesarrollo: i) haciendo una evaluación completa de la exposición de CEM-RF al cerebro, es decir, distinguiendo entre fuentes de CEM-RF con diferentes patrones de exposición al cerebro como las llamadas telefónicas, el uso de aparatos móviles de comunicación para actividades con pantalla y las fuentes ambientales, ii) estimando la cantidad de CEM- RF que el cerebro absorbe de cada fuente y en total, iii) evaluando el sueño utilizando medidas objetivas recogidas con actigrafia y iv) evaluando el neurodesarrollo como función cognitiva y volúmenes cerebrales. El uso de algunos dispositivos móviles de comunicación como por ejemplo la tableta y el uso problemático del teléfono móvil están associados con peor calidad y medidas objetivas del sueño. Además, hemos observado una asociación entre la dosis de CEM-RF al cerebro proveniente de las llamadas telefónicas por la tarde y peores medidas objetivas del sueño. En cuanto al neurodesarrollo, la dosis total de CEM-RF al cerebro y la dosis de CEM-RF al cerebro proveniente de las llamadas telefónicas no están asociadas con los volúmenes cerebrales, en cambio, la dosis de CEM-RF al cerebro proveniente de usos de aparatos móviles de comunicación para actividades con pantalla está asociada con un volumen más pequeño del núcleo caudado. Finalmente, la dosis total de CEM-RF al cerebro y la dosis de CEM-RF al cerebro proveniente de las llamadas telefónicas están asociadas con peor inteligencia no verbal. Teniendo en cuenta que se desconoce el mecanismo biológico que hay detrás de las asociaciones observadas entre la exposición a CEM-RF y el sueño y la exposición a CEM-RF y el neurodesarrollo, que los efectos que hemos encontrado son pequeños y que no hemos podido separar completamente entre los minutos de uso y la dosis de CEM-RF, nuestros resultados deben interpretarse con precaución. No podemos descartar hallazgo casual, causalidad inversa o que otros factores relacionados con el uso de dispositivos móviles de comunicación estén detrás de las asociaciones observadas. Por ejemplo, exposición a la luz azul, adicción a los dispositivos móviles de comunicación, excitación mental o desplazamiento del sueño.
L’ús de dispositius mòbils de comunicació com els telèfons mòbils, tauletes i ordinadors portàtils ha augmentat els darrers anys, especialment en preadolescents i adolescents. Els dispositius mòbils de comunicació utilitzen els camps electromagnètics de radiofreqüència (CEM-RF) per l’intercanvi constant d’informació necessari pel seu funcionament. L’evidència científica dels efectes que té l’exposició de CEM-RF al cervell és limitada i els estudis epidemiològics que avaluaven l’exposició de CEM-RF i la seva relació amb el son i el neurodesenvolupament són escassos. Aquesta tesi té com a objectiu entendre millor les associacions entre l’exposició a CEM-RF i el son i l’exposició a CEM-RF i el neurodesenvolupament. Per fer-ho: i) hem fet una avaluació completa de l’exposició de CEM-RF al cervell, és a dir, distingint entre fonts de CEM-RF amb diferents patrons d’exposició al cervell com les trucades telefòniques, l’ús d’aparells mòbils de comunicació per activitats amb pantalla i les fonts ambientals, ii) hem estimat la quantitat de CEM-RF que el cervell absorbeix de cada font i en total, iii) hem avaluat el son utilitzant mesures objectives recollides amb actigrafia i iv) hem avaluat el neurodesenvolupament com a funció cognitiva i volums cerebrals. L’ús d’alguns dispositius mòbils de comunicació com per exemple la tauleta i l’ús problemàtic del telèfon mòbil estan associats amb pitjor qualitat i mesures objectives del son. A més a més, hem trobat una associació entre la dosi de CEM-RF al cervell provinent de les trucades telefòniques al vespre i pitjors mesures objectives del son. En relació amb el neurodesenvolupament, la dosi total de CEM-RF al cervell i la dosi de CEM-RF al cervell provinent de les trucades telefòniques no estan associades amb els volums cerebrals, en canvi, la dosi de CEM-RF al cervell provinent d’usos d’aparells mòbils de comunicaió per activitats amb pantalla està associada amb un volum més petit del nucli caudat. Finalment, la dosi total de CEM-RF al cervell i la dosi de CEM-RF al cervell provinent de les trucades telefòniques estan associades amb pitjor la intel·ligència no verbal. Tenint en compte que es desconeix el mecanisme biològic que hi ha darrere de les associacions observades entre l'exposició a CEM-RF i el son i l'exposició a CEM-RF i el neurodesenvolupament, que els efectes que hem trobat són petits i que no hem pogut separar completament entre els minuts d'ús dels dispositius mòbils de comunicació i la dosi de CEM-RF al cervell, els nostres resultats s’han d’interpretar amb precaució. No podem descartar que les troballes siguin casuals, causalitat inversa o que altres factors relacionats amb l’ús de dispositius mòbils de comunicació estiguin darrere de les associacions observades. Per exemple, exposició a la llum blava, addicció als aparells mòbils de comunicació, excitació mental o desplaçament del son.

Abstract The aims of the present study were to clarify the antenna function and radio frequency radiation (RFR) sensitivity of human subjects using theoretical calculations and field tests. The weak very high frequency (VHF) electromagnetic fields and spontaneous hand movements were recorded. Groups of university students, other volunteers and as a very interesting group, experienced well finders, were used as test subjects. The VHF field was studied using a spectrum analyser and tuneable narrow-band or broad-band meter with a dipole antenna. The hand movements were registered by potentiometric systems and electromyography (EMG). The test subjects (altogether n = 140) in different tests were walking, sitting in a cart being pulled slowly forward, or sitting in a moving car. The responses were observed and hand movements were recorded and analysed by personal computers. By visual inspection and using the Pearson's correlation, the results of different individuals have been compared with the measured intensity of far fields of a radio mast. Reaction spots and graphs defined by different individuals in the same experiment areas have been compared to each other. Hand movement correlated with the reactions of the forearm and shoulder muscles, e.g., pronator teres and trapezius, by EMG measurements. The reactions of some persons correlated with each other. Experiments in a slow moving wagon and in a moving car showed a correlation between the test subjects’ hand movements and the intensity of below 1 mV/m radio and TV signals measured in the vicinity of the test subject. In open field tests different persons usually reacted in widely different ways. The most evident results were recorded near the buildings, where the radio waves reflected from the wall and patterns of standing waves were clear. Many VHF frequency modulated (FM) broadcasting signals were summed at these places at the same time. It is concluded that the spontaneous hand movement reactions occurred as a response of the human body to the gradients of the VHF field intensity. The reaction generally occurred in interference patterns of multipath propagation or standing waves originating from the radiation of FM radio and TV broadcasting transmitters and radiation reflected from the walls of buildings or from other objects. This non-thermal reaction was clearly observable as spontaneous arm movements by 39 percent of the 85 tested students
Tiivistelmä Tässä tutkimuksessa selvitettiin ihmisen herkkyyttä radiotaajuiselle säteilylle. Ihmisen toimimista radioaaltojen antennina tarkasteltiin teoreettisesti ja kenttäkokein. Heikkojen VHF-alueen radioaaltojen voimakkuutta ja tahattomia käsien liikkeitä rekisteröitiin valituilla koepoluilla. Koehenkilöinä on ollut yliopiston opiskelijoita ja muita vapaaehtoisten ryhmiä. Kiinnostavin ryhmä oli kokeneet kaivonkatsojat, joiden käsienliikereaktioihin radioaaltojen vaikutuksista löytyy viitteitä kirjallisuudesta. Radioaaltojen voimakkuuden vaihteluja mitattiin spektrianalysaattorilla ja laajakaistaisella VHF-alueen integroivalla mittarilla. Käsien liikkeitä rekisteröitiin potentiometriin perustuvilla liikeantureilla. Lihasten sähköimpulsseja rekisteröitiin elektromyografia- eli EMG-laitteella. Eri koesarjoissa koehenkilöt (yhteensä 140) kävelivät, istuivat hitaasti vedettävässä vaunussa tai istuivat liikkuvassa autossa. Reaktioita tarkkailtiin ja käsien liikkeet ja mitatut kentänvoimakkuudet rekisteröitiin ja analysoitiin tietokoneella. Eri koehenkilöiden tuloksia, reagointipaikkoja ja rekisteröityjä käyriä 5–35 km:n etäisyydellä mastoista tarkasteltiin silmämääräisesti. Pearsonin korrelaatiolaskentaa apuna käyttäen tuloksia verrattiin radiomastojen säteilyn voimakkuuteen. Eri ihmisten reagointikohtia ja käyriä samoilta koealueilta vertailtiin keskenään. Koeasetelmassa käsienliikkeiden todettiin korreloivan joidenkin kyynärvarren ja hartialihasten (mm. pronator teres ja trapezius) EMG-signaaleihin. Joidenkin koehenkilöiden tulokset korreloivat keskenään. Hitaasti vedettävässä vaunussa ja liikkuvassa autossa tehdyissä kokeissa tuli esille korrelaatio vartalon edessä olevien käsien loittonemis-lähestymis-liikkeiden ja koehenkilön välittömässä läheisyydessä mitattujen 1 mV/m -tasoisten radio- ja TV-signaalien voimakkuusvaihtelujen välillä. Avoimella kentällä henkilöt reagoivat hyvin eri tavoin. Parhaiten yhteys tuli esille rakennusten lähellä sijaitsevilla koealueilla, joissa radioaallot heijastuivat rakennuksen seinästä muodostaen selkeitä seisovan aallon kuvioita. Useat taajuusmoduloidut VHF-alueen radiosignaalit summautuivat näissä paikoissa samanaikaisesti. Johtopäätöksenä on, että tahattomat käsienliikkeet tapahtuvat kehon vasteena VHF-kentän voimakkuuden muutoksille. Reaktio tapahtui yleensä interferenssi-kuvioissa tai seisovissa aalloissa, jotka muodostuvat FM-radio- ja TV-lähetysten monitie-etenemisestä radioaaltojen heijastuessa rakennusten seinistä tai muista kohteista. Tämä ei-lämpövaikutustason reaktio oli selvästi havaittavissa olkapään tasalle koukistetun käden tahattomana ojennus-koukistus-liikkeenä 39 prosentilla testatuista 85 opiskelijasta

In the past, radio-frequency signals were commonly used for low-speed wireless electronic systems, and optical signals were used for multi-gigabit wired communication systems. However, as the emergence of new millimeter-wave technology introduces multi-gigabit transmission over a wireless radio-frequency channel, the borderline between radio-frequency and optical systems becomes blurred. As a result, there come ample opportunities to design and develop next-generation broadband systems to combine the advantages of these two technologies to overcome inherent limitations of various broadband end-to-end interconnect systems in signal generation, recovery, synchronization, and so on. For the transmission distances of a few centimeters to thousands of kilometers, the convergence of radio-frequency electronics and optics to build radio-over-fiber systems ushers in a new era of research for the upcoming very-high-throughput broadband services. Radio-over-fiber systems are believed to be the most promising solution to the backhaul transmission of the millimeter-wave wireless access networks, especially for the license-free, very-high-throughput 60-GHz band. Adopting radio-over-fiber systems in access or in-building networks can greatly extend the 60-GHz signal reach by using ultra-low loss optical fibers. However, such high frequency is difficult to generate in a straightforward way. In this dissertation, the novel techniques of homodyne and heterodyne optical-carrier suppressions for radio-over-fiber systems are investigated and various system architectures are designed to overcome these limitations of 60-GHz wireless access networks, bringing the popularization of multi-gigabit wireless networks to become closer to the reality. In addition to the advantages for the access networks, extremely high spectral efficiency, which is the most important parameter for long-haul networks, can be achieved by radio-over-fiber signal generation. As a result, the transmission performance of spectrally efficient radio-over-fiber signaling, including orthogonal frequency division multiplexing and orthogonal wavelength division multiplexing, is broadly and deeply investigated. On the other hand, radio-over-fiber is also used for the frequency synchronization that can resolve the performance limitation of wireless interconnect systems. A novel wireless interconnects assisted by radio-over-fiber subsystems is proposed in this dissertation. In conclusion, multiple advantageous facets of radio-over-fiber systems can be found in various levels of end-to-end interconnect systems. The rapid development of radio-over-fiber systems will quickly change the conventional appearance of modern communications.

Electromagnetic waves can be used to transmit information over long distances and are therefore often employed for communication purposes. The electromagnetic waves are reflected off material objects on their paths and interact with the medium through which they propagate. For instance, the plasma in the ionosphere can refract and even reflect radio waves propagating through it. By increasing the power of radio waves injected into the ionosphere, the waves start to modify the plasma, resulting in the generation of a wide range of nonlinear processes, including turbulence, in particular near the reflection region. By systematically varying the injected radio waves in terms of frequency, power, polarisation, duty cycle, inclination, etc. the ionosphere can be used as an outdoor laboratory for investigating fundamental properties of the near-Earth space environment as well as of plasma turbulence. In such ionospheric modification experiments, it has been discovered that the irradiation of the ionosphere by powerful radio waves leads to the formation of plasma density structures and to the emission of secondary electromagnetic radiation, a phenomenon known as stimulated electromagnetic emission. These processes are highly repeatable and have enabled systematic investigations of the nonlinear properties of the ionospheric plasma. In this thesis we investigate features of the plasma density structures and the secondary electromagnetic radiation. In a theoretical study we analyse a certain aspect of the formation of the plasma structures. The transient dynamics of the secondary radiation is investigated experimentally in a series of papers, focussing on the initial stage as well as on the decay. In one of the papers we use the transient dynamics of the secondary radiation to reveal the intimate relation between certain features of the radiation and structures of certain scales. Further, we present measurements of unprecedentedly strong secondary radiation, attributed to stimulated Brillouin scattering, and report measurements of the secondary radiation using a novel technique imposed on the transmitted radio waves.

With the increasing demand on wireless and portable devices, the radio frequency front end blocks are required to feature properties such as wideband, high frequency, multiple operating frequencies, low cost and compact size. However, the current radio frequency system blocks are designed by combining several individual frequency band blocks into one functional block, which increase the cost and size of devices. To address these issues, it is important to develop novel approaches to further advance the current design methodologies in both space and spectrum domains. In recent years, the concept of artificial materials has been proposed and studied intensively in RF/Microwave, Terahertz, and optical frequency range. It is a combination of conventional materials such as air, wood, metal and plastic. It can achieve the material properties that have not been found in nature. Therefore, the artificial material (i.e. meta-materials) provides design freedoms to control both the spectrum performance and geometrical structures of radio frequency front end blocks and other high frequency systems. In this dissertation, several artificial materials are proposed and designed by different methods, and their applications to different high frequency components and circuits are studied. First, quasi-conformal mapping (QCM) method is applied to design plasmonic wave-adapters and couplers working at the optical frequency range. Second, inverse QCM method is proposed to implement flattened Luneburg lens antennas and parabolic antennas in the microwave range. Third, a dual-band compact directional coupler is realized by applying artificial transmission lines. In addition, a fully symmetrical coupler with artificial lumped element structure is also implemented. Finally, a tunable on-chip inductor, compact CMOS transmission lines, and metamaterial-based interconnects are proposed using artificial metal structures. All the proposed designs are simulated in full-wave 3D electromagnetic solvers, and the measurement results agree well with the simulation results. These artificial material-based novel design methodologies pave the way toward next generation high frequency circuit, component, and system design.

This thesis describes design of Simulator FM-CW range finders. It is choosing the optimal method of realization and inform about basic properties of continuous working radar. The work includes an analysis of errors in real rangefinder and a numerical estimate of the maximum error in real devices. Contains detailed block diagram of simulator FM-CW range-finder and computer simulation of function generator frequency modulated signal, demodulator. Further work includes the complete construction documents for the preparation and implementation of basic functional verification

Depuis plusieurs années, les technologies de l’information et de la communication connaissent un développement spectaculaire. Le trafic d’information augmente exponentiellement alors que l’évolution de l’efficacité énergétique des réseaux, définie généralement comme le rapport entre l’énergie utile en sortie du système et l’énergie totale fournie au système, n’augmente que de manière linéaire. Pour soutenir la demande de trafic, il est alors nécessaire de multiplier les équipements réseaux ce qui augment la facture énergétique des opérateurs et les émissions de gaz carbonique. Devant l’urgence de la situation, de nombreux projets et consortiums ont été créés avec l’objectif de renforcer l’efficacité énergétique des réseaux. Par exemple, le consortium GreenTouch™ fondé en 2010 a pour objectif d’améliorer l’efficacité énergétique des réseaux d’un facteur 1000 d’ici 2015 et de réduire leur consommation énergétique de 90% d’ici 2020 (par rapport à 2010). Le projet METIS a pour objectif de définir les télécommunications de 2020 (5G) cherche des solutions efficaces minimisant les coûts, les ressources et la consommation énergétique. Le projet MiWEBA qui intègre les ondes millimétrique aux communications mobiles dans le but d’augmenter la capacité du réseau d’un facteur 1000 avec un coût raisonnable.Dans cette thèse, nous abordons deux solutions répondant aux challenges de la 5G et permettant de réduire les niveaux des puissances rayonnées par les systèmes de télécommunications : l’amélioration de la couche physique via les techniques de focalisation spatiale et l’adaptation de lien multi-technologies. L’objectif principal de la thèse est de réaliser des transmissions de données très haut débit à forte efficacité énergétique à l’aide d’une connectivité multi-technologies sans coutures y compris dans des réseaux comprenant une multitude de périphériques à faible complexité.L’organisation de la thèse est la suivante : tout d’abord, l’implémentation de techniques de focalisation spatiale, le Retournement Temporel (RT) et l’EGT (Equal Gain Transmission), dans un système utilisant les dernières évolutions du standard IEEE 802.11, notamment l’intégration d’une composante 60 GHz, est étudiée. Les performances de ces techniques sont analysées de manière à identifier les conditions optimales de leur utilisation et il est montré qu’avec un minimum de deux antennes de transmission, elles permettent d’améliorer les performances énergétiques des systèmes tout en ayant une faible complexité d’implémentation. Des modifications du standard permettant d’augmenter l’efficacité énergétique sont également proposées. Une analyse cross-layer est ensuite réalisée afin de définir protocoles d’estimation de canal tenant compte des spécificités du RT. De plus, les améliorations énergétiques liées à l’utilisation du RT sont confirmées en tenant compte des dégradations des performances de la couche de liaison. Enfin, une métrique d’occupation temporelle est définie et associée à des techniques d’adaptation de lien mono et multi-technologies existantes dans le but d’améliorer la sélection d‘interfaces de transmission pour augmenter l’efficacité énergétique sans affecter les performances des systèmes utilisant un accès aléatoire au canal de communication. L’utilisation de cette métrique permet, dans certaines configurations, d’augmenter d’un facteur sept l’efficacité énergétique d’un système utilisant le Wi-Fi et, dans le cas multi-technologies, de répartir le trafic sur les différentes interfaces de transmission afin d’éviter la saturation des canaux de communication
Over the past few years, information and communications technologies have experienced a spectacular development. Traffic demand grows exponentially while energy efficiency of networks –usually defined as the ratio between delivered power and supplied power- only increases linearly. In order to supply the data traffic, it is necessary to duplicate networks equipments increasing energy costs for operators and carbon dioxide emissions. To face this dramatic situation, several projects and consortiums have been created and aim to increase networks energy efficiency. For instance, the GreenTouch™ consortium funded in 2010 aims to improve networks energy efficiency by a factor 1000 by 2015 and to reduce energy consumption of TICs by 90% by 2020 (compared with 2010 levels). METIS project aims to define 2020s communications (5G) search for efficient solutions with low costs, low resources use and low power consumption of systems. MiWEBA project brings millimeter-waves into the mobile radio word to extend the network capacity by 1000 at reasonable cost.In this thesis we study two solutions to answer 5G challenges and reduce radiated power levels of telecommunications systems: physical layer improvements through spatial focalization techniques and multi-technologies link adaptation. This thesis main goal is to achieve very high data transmission rates with high energy efficiency and seamless connectivity using multiple-interfaces technologies even in networks composed of a high number of low-complexity devices.The thesis is organized as follows: first, Time Reversal (TR) and Equal Gain Transmission (EGT) implementation is studied and applied to a system using the latest amendments of IEEE 802.11 standard, including 60 GHz transmissions. Performance of these techniques is analyzed in order to identify optimal conditions of use and it is shown that they only require a minimum of two transmit antennas to increase the energetic performance of systems while having a low implementation complexity. Standard modifications allowing an increase of energy efficiency are proposed. Then, a cross-layer analysis is performed to define channel estimation protocols taking TR specificities into account. Moreover, TR energetic benefits are validated considering its drawbacks at the link layer level. Finally, a time-availability metric is defined and associated to existing mono or multi-technologies adaptation techniques and aim to increase energy efficiency without degrading the performance of systems using random access to the communication channel. This metrics allows –in some configurations- to increase by a factor seven the energy efficiency of a system using Wi-Fi and, in a multi-technologies scenario, to allocate the data traffic to the several interfaces in order to avoid communication channels saturation

La thèse, dont le sujet est "Modélisation de la propagation électromagnétique en milieux à gradient d'indice basée sur les faisceaux gaussiens - Application à la propagation en atmosphère réaliste et à la radio-occultation entre satellites" a été commencée le 2 décembre 2013, au Département ÉlectroMagnétisme et Radar (DEMR) de l'Onera de Toulouse et avec le laboratoire LAPLACE de l'Université Paul Sabatier. Elle est co-financée par l'ONERA et par la Région Midi-Pyrénées. L'encadrement a été assuré par Jérôme Sokoloff (Laplace/UPS, directeur de thèse), Alexandre Chabory (ENAC, co-directeur) et Vincent Fabbro (ONERA). L'École Doctorale est l' "École Doctorale Génie Électrique, Électronique, Télécommunications : du système au nanosystème". Le faisceau gaussien a été principalement utilisé dans la recherche scientifique afin d'étudier les systèmes optiques tels que les lasers. Des études plus rares et plus récentes ont proposé de l'utiliser pour modéliser la propagation des ondes sismiques. Ses propriétés spatiales et spectrales ont amené certains auteurs à étudier son utilisation dans des modèles de propagation atmosphériques. Cette thèse a consisté à développer un modèle, appelé GBAR (Gaussian Beam for Atmospheric Refraction), de propagation troposphérique réaliste et déterministe en utilisant le formalisme des faisceaux gaussiens. La démarche adoptée a consisté à reprendre les équations fondamentales introduites par Cerveny et Popov décrivant de façon itérative la propagation d'un faisceau gaussien en milieu inhomogène, sous hypothèse de haute fréquence (modèle asymptotique). De nouvelles équations ont été développées à partir d'elles pour obtenir une description analytique de la propagation d'un faisceau gaussien dans un milieu troposphérique décrit par les variations spatiales de l'indice de réfraction. L'hypothèse de base pour l'obtention de la formulation analytique est que le gradient de l'indice de réfraction peut être considéré vertical et constant au voisinage du faisceau. Les équations analytiques pour la description de la propagation d'un seul faisceau ont ensuite été étendues à la modélisation d'un champ quelconque dans un milieu troposphérique pouvant contenir de fortes variations du gradient d'indice, y compris des inversions de gradient. Ceci a été réalisé en couplant les équations analytiques avec la procédure de décomposition multi-faisceaux développée dans sa thèse pas Alexandre Chabory. Le modèle GBAR a été validé dans des milieux troposphériques réalistes issus de simulations du modèle météo méso-échelle WRF (Weather Research and Forecasting). Dans un troisième temps, le modèle a été utilisé pour simuler des inversions de données de radio-occultation. Des outils existent pour fournir un modèle d'interprétation de ces données pour estimer les propriétés physiques de l'atmosphère à partir des mesures en phase, amplitude, Doppler et délai des signaux GNSS transmis entre satellites en orbite autour de la Terre
The subject of this PhD thesis is " Electromagnetic propagation modeling in inhomogeneous media with refractive index gradients based on Gaussian beams - Application to realistic atmospheric propagation and radio occultation between satellites ". The study started on december 2nd, 2013 at the DEMR (Département Électromagnétisme et Radar) department of the ONERA research laboratory, in Toulouse, France. It was funded both by the ONERA and Région Midi-Pyrénées. It was supervised by Jérôme Sokoloff (LAPLACE/UPS, thesis director), Alexandre Chabory (ENAC, thesis co-director) and Vincent Fabbro (ONERA). The doctoral school was "École Doctorale Génie Électrique, Électronique, Télécommunications : du système au nanosystème ". The Gaussian beam was mostly used in scientific investigations to study optical systems such as lasers. Rarer and more recent works suggested the use of the Gaussian beam formalism in order to model the propagation of seismic waves. The properties of the Gaussian beam also led some authors to develop models for atmospheric propagation. In this thesis a model based on Gaussian beams called GBAR (Gaussian Beam for Atmospheric Refraction) was developped for tropospheric propagation in realistic and deterministic conditions. The scientific approach consisted in rewritting the fundamental equations introduced by Cerveny and Popov describing iteratively the propagation of a Gaussian beam in inhomogeneous media, under the high-frequency assumption (asymptotic model). New equations were derived from them in order to get analytical equations of the propagation of a Gaussian beam in inhomogeneous media described by the variations of the refractive index. The basic assumption under to get the analytical equations is to consider that the refractive index gradient is vertical and constant around the beam axis. The analytical equations that describe the propagation of a Gaussian beam were extended to model the propagation of an arbitrary field in a tropospheric medium with strong variations and inversions of the refractive index. This was done by coupling the analytical equations with the multibeam expansion procedure developped by Alexandre Chabory in his PhD thesis. The GBAR model was validated in tropospheric conditions, using refractive index grids from the WRF (Weather Research and Forecasting) mesoscale meteorological model. In the third and final phase, the GBAR model was used to simulate Radio Occultation data inversions. Tools exist to allow for interpretations of Radio Occultation data in order to estimate the physical properties of the atmosphere from measured phased, amplitude, Doppler shift and delay of GNSS signals transmitted between satellites orbiting around the Earth

The radio frequency (RF) electromagnetic field (EMF) exposure of a 5G small cell radiobase station (RBS) using massive MIMO antenna is assessed. The compliance distance for auniform antenna excitation is determined for a 4x4- and an 8x8 planar array antenna at fourdifferent carrier frequencies, 10, 15, 28 and 60 GHz. Three different exposure standards areused to find the compliance distance, the ICNIRP-, the FCC- and a draft IEEE standard.Simulations using the method of moments (MoM) was used to analyze the antennas and calculatethe power density. The compliance distance converges to Fries far field formula in thefar field region, where said formula is valid. Each standard use different averaging areas andthe convergence is slower for a larger averaging area. This can be explained by the act ofaveraging working as a low pass filter. A lower frequency also leads to a slower convergence,as the far field is located further away.A statistical model is developed to assess the time-averaged realistic maximum power level,based on a 8x8 planar array antenna using a carrier frequency of 28 GHz. Parameters such asTDD, user position and utilization are considered and the model is valid in both the near fieldand the far field regions. The user positions are determined to obtain a realistic conservativeRF EMF exposure with a confidence level of 95%. The antenna can transmit the signal in adefined set of 47 different beam directions spanning -60 to 60 degrees in azimuth and -15 to15 degrees in elevation. The set of 47 beams are simulated using the method of moments tocalculate the electromagnetic fields in the vicinity of the RBS antenna. For the user distributionsinvestigated and at a distance of 20 cm, the power reduction factor is below 0.22. Asthe distance becomes larger the power reduction factor converges toward around 0.17 usinga weighted user distribution and toward 0.10 using a uniform user distribution. This impliesthat the compliance distance can be reduced significantly compared with the results using thetheoretical maximum power.A four panel model is created with the same input parameters as in the one panel case. Themodel is based on a small cell radio base station product produced by Ericsson. A statisticalmodel is created to assess the RF exposure which are made to converge towards the one panelcase far away from the antenna. The users are distributed uniformly and separately over the4 panels with priority given to the panels with highest exposure. The power reduction factoris one forth of the single panel case close to the antenna and converges toward the single panelresults. In general, a four panel product will also have a significant reduction in compliancedistance compared to the results obtained by using constant maximum power.

In today's rapidly expanding communications industry, there is an ever-increasing demand for greater bandwidth, higher data rates and better spectral efficiency. As a result current and future communication systems will need to employ advanced spatial, temporal and frequency diversity techniques in order to meet these demands. Even with the utilisation of such techniques, the congestion of the lower frequency bands, will inevitably lead to the increased usage of the millimetre-wave frequencies in terrestrial communication systems. Before such systems can be deployed, radio system designers require realistic and readily useable channel and propagation models at their disposal to predict the behaviour of such communication links and ensure that reliable and efficient data transmission is achieved The scattering and attenuation of electromagnetic waves by rain is a serious problem for microwave and millimetre-wave frequencies. The conversion of rain rate to specific attenuation is a crucial step in the analysis of the total path attenuation and hence radio-link availability. It is now common practice to relate the specific attenuation and the rain rate using the simple power law relationship. The power-law parameters are then used in the path attenuation model, where the spatial variations of rainfall are estimated by a path-integration of the rain rate. These power law parameters are strongly influenced by the drop-size-distribution (DSD). Thus an examination of the various DSDs and their influence on the specific attenuation and link availability is warranted. Several models for the DSD have been suggested in literature, from the traditional exponential, to the gamma, log normal and Weibull distributions. The type of DSD varies depending on the geographical location and rainfall type. An important requirement of the DSD is that it is consistent with rain rate (i.e. the DSD must satisfy the rain-rate integral equation). Thus before application in the specific attenuation calculations, normalisation needs to be performed to ensure the consistency, as done in this study. Once the specific attenuation has been evaluated for necessary frequency and rain-rate range, path averaging is performed to predict the rain attenuation over the communication link. The final step in this dissertation is the estimation of the percentage of time of such occurrences. For this, cumulative time statistics of surface point rain rates are needed. The resulting cumulative distribution model of the fade depth and duration due to rain is a valuable tool for system designers. With such models the system designer can then determine the appropriate fade margin for the communication system and resulting period of unavailability for the link
Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2006.

Hu Mengna.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2004.
Includes bibliographical references (leaves 102-105).
Abstracts in English and Chinese.
Abstract --- p.ii
Acknowledgements --- p.iv
Table of Contents --- p.v
Chapter Chapter 1 --- Introduction --- p.1
Chapter 1.1 --- PEEC Modeling Method --- p.1
Chapter 1.2 --- Overview of the work --- p.2
Chapter 1.3 --- Original Contributions --- p.3
Chapter 1.4 --- Organization of the thesis --- p.3
Chapter Chapter 2 --- CLASSICAL PARTIAL ELEMENT EQUIVALENT CIRCUIT MODELING --- p.4
Chapter 2.1 --- Introduction --- p.4
Chapter 2.2 --- Mathematical Formulation in PEEC --- p.5
Chapter 2.2.1 --- Basic Integral Equation --- p.5
Chapter 2.2.2 --- Current and Charge discretization --- p.6
Chapter 2.2.3 --- Galerkin Matching Method --- p.8
Chapter 2.3 --- Partial Inductance --- p.10
Chapter 2.3.1 --- General Formula for partial mutual inductance --- p.10
Chapter 2.3.2 --- Mutual Inductance between two Thin Rectangular Tapes --- p.11
Chapter 2.4 --- Partial Capacitance --- p.13
Chapter 2.4.1 --- General Formula for partial mutual capacitance --- p.13
Chapter 2.4.2 --- Mutual Capacitance Between Two Thin Rectangular Tapes --- p.16
Chapter 2.5 --- Meshing Scheme --- p.17
Chapter 2.6 --- Green's function --- p.20
Chapter 2.6.1 --- Modification on free space Green's function through Ray-tracing technique --- p.20
Chapter 2.6.2 --- Impact on partial inductance and partial capacitance --- p.22
Chapter 2.7 --- PEEC Modeling of A LTCC 2.4GHz Band Pass Filter --- p.23
Chapter 2.7.1 --- General Procedures to apply PEEC Modeling Method --- p.23
Chapter 2.7.2 --- Numerical Results of a LTCC Band Pass Filter Modeling --- p.24
Chapter 2.8 --- Summary --- p.27
Chapter Chapter 3 --- GENERALIZED PEEC MODELING FOR PASSIVE COMPONENT OF IRREGULAR SHAPES --- p.29
Chapter 3.1 --- Introduction --- p.29
Chapter 3.2 --- Triangular meshing scheme in MoM --- p.30
Chapter 3.2.1 --- Triangular meshing scheme adopted in MoM --- p.30
Chapter 3.2.2 --- Spiral Inductor --- p.32
Chapter 3.3 --- Generalized Meshing Scheme --- p.34
Chapter 3.4 --- Mathematical Formulation in Enhanced PEEC --- p.39
Chapter 3.4.1 --- Current and Charge discretization --- p.39
Chapter 3.4.2 --- Enhanced Formulation for partial mutual inductance and capacitance --- p.41
Chapter 3.4.3 --- Four-Dimensional Integration --- p.43
Chapter 3.4.4 --- Gauss Numerical Integration --- p.44
Chapter 3.4.5 --- Mixed Numerical and Analytical Technique --- p.47
Chapter 3.5 --- Numerical Results from Enhanced PEEC Modeling Method --- p.50
Chapter 3.5.1 --- Spiral Inductor --- p.50
Chapter 3.5.2 --- High Pass Filter --- p.56
Chapter 3.5.3 --- Design and Optimization of LTCC Diplexer --- p.60
Chapter 3.6 --- Summary --- p.67
Chapter Chapter 4 --- HIGH FREQUENCY PEEC --- p.69
Chapter 4.1 --- Introduction --- p.69
Chapter 4.2 --- Spatial Domain Green's Functions --- p.70
Chapter 4.2.1 --- Full-wave Spectral Domain Green´ةs Functions --- p.70
Chapter 4.2.2 --- Full-wave Spatial Domain Green，s functions --- p.72
Chapter 4.3 --- Frequency-dependent Complex Partial Elements --- p.74
Chapter 4.4 --- Numerical Results Of High-Frequency PEEC Modeling Method --- p.79
Chapter 4.4.1 --- Numerical Discussion of Complex Image Method --- p.75
Chapter 4.4.2 --- Microstrip Filter --- p.84
Chapter 4.4.3 --- Patch Antenna --- p.84
Chapter 4.5 --- Summary --- p.87
Chapter Chapter 5 --- CONCLUDING REMARKS --- p.88
Chapter 5.1 --- Two Enhancements in PEEC Modeling --- p.88
Chapter 5.2 --- Limitations of Enhanced PEEC Modeling --- p.90
Chapter 5.3 --- Future Work --- p.90
APPENDIX --- p.92
REFERENCE --- p.102

We developed a self-consistent model of helicon discharges, motivated by a number of applications. One example is a plasma-based space propulsion system that employs a helicon discharge as its plasma source. Our study of helicon discharges involves two steps. An electro-magnetic wave solver is first developed to study wave phenomena and power deposition. In this work, we model a resonant response of the discharge observed in a recent experiment. The radially localized helicon (RLH) wave is identified as the primary mechanism of rf-power deposition into the plasma. The second step is to take into account electron heat transfer and ion transport so that a self-consistent simulation can be performed. As a case study of validating the model, we simulated one of Boswell’s early experiment in which a jump of plasma density in a scan of external magnetic field is observed. Calculation shows that a classical heat transport is unable to sustain the plasma density profile observed in the experiment. Solutions comparable to the experiment are obtained only when extra heat conductivity is used. The density profiles and excited wave-lengths are in good agreement with the experiment. Especially, the dual-stable solution of the simulation supports the observed plasma density jump.
text

This thesis describes a brief history of radio and electromagnetic waves from a physical point of view. It focuses mainly on radio waves in the VHF and subsequent construction of a radio network in this band. It uses the knowledge of the writer of this wavelength. This thesis is intended as a guide for fellow author.

Dissertação de Mestrado em Geociências apresentada à Faculdade de Ciências e Tecnologia
Direct observation of the geology and geological structures in the subsurface is obviously difficult, therefore the ability to make this information gap achievable is of particular interest.This study intends to observe the configuration, the structure of detail and the constituent materials of the alluvial body, located in the alluvial plain of Baixo Mondego, in Tentúgal. For this, a geophysical exploration method was used, in which its application has the porpuse of define large units of the Mondego alluvium, to identify radar facies in the defined units and to recognize possible paleochannels of the Mondego river in Tentúgal.The necessity to obtain a fast data acquisition method, with easy-to-handle means, without much logistics or personnel, which was not invasive or destructive and obviously low cost, has made the ground penetrating radar technique a relevant option.The operating principle of ground penetrating radar, which is an electromagnetic method, consists of the emission of electromagnetic waves generated by a short high-frequency pulse, emitted to the ground by a transmitting antenna, that are later received by a receiving antenna. The raw data obtained goes through a key step, which corresponds to the processing. At this stage the use of a multi-step processing stream is intended to provide sections with improved visual appearance for clearer and more accurate interpretation.After the processing phase the interpretation of the radargrams is followed. The interpretation basically consists of the association of reflection patterns to a given structure, lithology or discontinuity.As a result of the interpretation of the ground penetrating radar sections, two main units were identified. An upper unit, where reflectors with different configurations and patterns are visible and where it is possible to identify various radar facies. This unit will correspond to sandy material more or less coarse, with possible alternation of finer levels. In the lower unit, a clear attenuation of the signal is evident, which results in an absence of reflections, which will be associated to a unit of materials with important clay fraction.In order to obtain an overview of the total area of the survey, a map of the upper unit configuration was constructed, and it was possible to recognize and define the paleochannel geometry.Ground penetrating radar has shown to be a very efficient tool in the definition of large units and the observation of the detailed sedimentary structure in relation to the radar facies identified. It was also possible to confirm that the signal undergoes strong attenuation in the presence of clayey materials, which limits its penetration in depth.
A observação directa da geologia e de estruturas geológicas que se encontram na subsuperfície é evidentemente difícil, por consequente, a capacidade de tornar esta lacuna de informação alcançável tem particular interesse.Com este estudo pretende-se observar a configuração, a estrutura de pormenor e os materiais constituintes do corpo aluvionar, localizado na planície aluvial do Baixo Mondego, em Tentúgal. Para tal, foi utilizado um método de exploração geofísico, em que a sua aplicação tem o propósito de definir grandes unidades das aluviões do Mondego, de identificar fácies de radar nas unidades definidas e reconhecer possíveis paleocanais do rio Mondego em Tentúgal.A necessidade de ter um método de rápida aquisição de dados, com meios de fácil manuseamento, sem necessidade de muita logística nem pessoal, que não seja nem invasivo nem destrutivo e obviamente que tivesse custos reduzidos, fez com que a técnica do geo-radar fosse uma opção de relevância.O princípio de funcionamento do geo-radar, sendo este um método electromagnético, consiste na emissão de ondas electromagnéticas geradas através de um curto pulso de alta frequência, emitidas para o terreno por uma antena transmissora, que são posteriormente recebidas por uma antena receptora. Os dados brutos obtidos sofrem uma etapa chave, que corresponde ao processamento. Nesta fase a utilização de um fluxo de processamento em vários passos tem como finalidade obter secções com aspecto visual melhorado para que a interpretação seja mais clara e precisa. Após a fase de processamento segue-se a interpretação dos radargramas. A interpretação, basicamente, consiste na associação de padrões de reflexão a uma determinada estrutura, litologia ou descontinuidade. Como resultado da interpretação das secções de geo-radar foram identificadas duas unidades principais. Uma unidade superior, onde são visíveis reflectores com diferentes configurações e padrões e onde é possível identificar várias fácies de radar. Esta unidade corresponderá a material arenoso mais ou menos grosseiro, com possível alternância de níveis mais finos. Na unidade inferior é evidente uma clara atenuação do sinal, que se traduz numa ausência de reflexões, que estará associada a uma unidade de materiais com fracção argilosa importante. De modo a adquirir uma perspectiva geral da área total do levantamento foi construído um mapa da configuração da unidade superior, tendo sido possível reconhecer e definir a geometria de paleocanais. O geo-radar mostrou ser uma ferramenta bastante eficiente no que diz respeito à definição de grandes unidades e na observação da estrutura sedimentar de pormenor, em relação com as fácies de radar identificadas. Foi ainda possível constatar que o sinal sofre forte atenuação na presença de materiais argilosos, o que limita a sua penetração em profundidade.

abstract: High Impedance Surfaces (HISs), which have been investigated extensively, have proven to be very efficient ground planes for low profile antenna applications due to their unique reflection phase characteristics. Another emerging research field among the microwave and antenna technologies is the design of flexible antennas and microwave circuits to be utilized in conformal applications. The combination of those two research topics gives birth to a third one, namely the design of Conformal or Flexible HISs (FHISs), which is the main subject of this dissertation. The problems associated with the FHISs are twofold: characterization and physical realization. The characterization involves the analysis of scattering properties of FHISs in the presence of plane wave and localized sources. For this purpose, an approximate analytical method is developed to characterize the reflection properties of a cylindrically curved FHIS. The effects of curvature on the reflection phase of the curved FHISs are examined. Furthermore, the effects of different types of currents, specifically the ones inherent to finite sized periodic structures, on the reflection phase characteristics are observed. After the reflection phase characterization of curved HISs, the performance of dipole antennas located in close proximity to a curved HIS are investigated, and the results are compared with the flat case. Different types of resonances that may occur for such a low-profile antenna application are discussed. The effects of curvature on the radiation performance of antennas are examined. Commercially available flexible materials are relatively thin which degrades the bandwidth of HISs. Another practical aspect, which is related to the substrate thickness, is the compactness of the surface. Because of the design limitations of conventional HISs, it is not possible to miniaturize the HIS and increase the bandwidth, simultaneously. To overcome this drawback, a novel HIS is proposed with a periodically perforated ground plane. Copper plated through holes are extremely vulnerable to bending and should be avoided at the bending parts of flexible circuits. Fortunately, if designed properly, the perforations on the ground plane may result in suppression of surface waves. Hence, metallic posts can be eliminated without hindering the surface wave suppression properties of HISs.
Dissertation/Thesis
Ph.D. Electrical Engineering 2013

A doubly resonant cavity was used to search for nonlinear radiofrequency (RF) energy conversion in a range of biological preparations, thereby testing the hypothesis that living tissue can demodulate RF carriers and generate baseband signals. The samples comprised high-density cell suspensions (human lymphocytes and mouse bone marrow cells); adherent cells (IMR-32 human neuroblastoma, G361 human melanoma, HF-19 human fibroblasts, N2a murine neuroblastoma (differentiated and non-differentiated) and Chinese hamster ovary (CHO) cells) and thin sections or slices of mouse tissues (brain, kidney, muscle, liver, spleen, testis, heart and diaphragm). Viable and non-viable (heat killed or metabolically impaired) samples were tested. Over 500 cell and tissue samples were placed within the cavity, exposed to continuous wave (CW) fields at the resonant frequency (f) of the loaded cavity (near 883 MHz) using input powers of 0.1 or 1 mW, and monitored for second harmonic generation by inspection of the output at 2f. Unwanted signals were minimised using low pass filters (/= 1 GHz) at the output from, the cavity. A tuned low noise amplifier allowed detection of second harmonic signals above a noise floor as low as -169 dBm. No consistent second harmonic of the incident CW signals was detected. Therefore, these results do not support the hypothesis that living cells can demodulate RF energy, since second harmonic generation is the necessary and sufficient condition for demodulation.