Дисертації з теми "100501 Antennas and Propagation"
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Vural, Serdar. "Information propagation in wireless sensor networks using directional antennas." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1188006033.
Повний текст джерелаHope, David C. "Towards a wireless aircraft : propagation, antennas and radio standards." Thesis, University of York, 2011. http://etheses.whiterose.ac.uk/1900/.
Повний текст джерелаWu, Xianyue. "Antennas and propagation for body area networks at 60 GHZ." Thesis, University of Birmingham, 2014. http://etheses.bham.ac.uk//id/eprint/4786/.
Повний текст джерелаAllen, Ben. "Smart antennas for high data rate FDD wireless links." Thesis, University of Bristol, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364956.
Повний текст джерелаTsivgoulis, Georgios. "Source localization in wireless sensor networks with randomly distributed elements under multipath propagation conditions." Thesis, Monterey, Calif. : Naval Postgraduate School, 2009. http://edocs.nps.edu/npspubs/scholarly/theses/2009/March/09Mar%5FTsivgoulis.pdf.
Повний текст джерелаThesis Advisor(s): Tummala, Murali ; McEachen, John C. "March 2009." Description based on title screen as viewed on April 23, 2009. Author(s) subject terms: Wireless Sensor Network, Direction of Arrival, DOA, Random Arrays, Smart Antennas, Time Difference of Arrival, TDOA, Multipath Propagation, Source Localization. Includes bibliographical references (p. 89-92). Also available in print.
Kavak, Adnan. "Vector propagation channel studies for smart antenna wireless communication systems /." Full text (PDF) from UMI/Dissertation Abstracts International, 2000. http://wwwlib.umi.com/cr/utexas/fullcit?p3004302.
Повний текст джерелаChang, Teck Keng. "Active frequency selective surfaces." Thesis, University of Kent, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.281659.
Повний текст джерелаSani, Andrea. "Modelling and characterisation of antennas and propagation for body-centric wireless communication." Thesis, Queen Mary, University of London, 2010. http://qmro.qmul.ac.uk/xmlui/handle/123456789/596.
Повний текст джерелаIbraheem, Ali Ahmed Younis. "Implanted Antennas and Intra-Body Propagation Channel for Wireless Body Area Network." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/50936.
Повний текст джерелаPh. D.
Fragoulis, Ioannis. "An investigation of two broadband HF shipboard communication antennas." Thesis, Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA245608.
Повний текст джерелаThesis Advisor(s): Adler, Richard W. Second Reader: Vincent, Wilbur R. "December 1990." Description based on title screen as viewed on March 30, 2010. DTIC Identifier(s): Ship Antennas, Communication Antennas, Antenna Radiation Patterns, High Frequency, Multiwire Antennas, Theses. Author(s) subject terms: Inverted Cone Antenna, Computer Antenna Modeling, NEC, HF Antennas, Shipboard Antenna. Includes bibliographical references (p. 95). Also available in print.
Schulte, Joseph Thomas 1957. "A system to measure the phase shift and attenuation of underground HF electromagnetic propagation." Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/277177.
Повний текст джерелаCooper, James Roger. "Novel wireless sensor configurations incorporating isotropic radiators on conformal artificial magnetic conductors." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/52246.
Повний текст джерелаBurge, Joseph. "Polarisation MIMO indoor wireless communications using highly compact antennas and platforms." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/polarisation-mimo-indoor-wireless-communications-using-highly-compact-antennas-and-platforms(e23fb834-e17e-4434-88c9-90c57d99e055).html.
Повний текст джерелаGriffin, Joshua David. "High-frequency modulated-backscatter communication using multiple antennas." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28087.
Повний текст джерелаCommittee Chair: Durgin, Gregory; Committee Member: Ingram, Mary Ann; Committee Member: Nikitin, Pavel; Committee Member: Peterson, Andrew; Committee Member: Steffes, Paul.
Wang-Hurst, Kathy Weiquan. "Analysis of Path Loss from a Transmitter in an Aircraft Cabin to an Exterior Fuselage-Mounted Antenna." Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/36237.
Повний текст джерелаMaster of Science
Aagaard, Fransson Erik Johannes, and Tobias Wall-Horgen. "Building and Evaluating a 3D Scanning System for Measurementsand Estimation of Antennas and Propagation Channels." Thesis, KTH, Elektroteknisk teori och konstruktion, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-104802.
Повний текст джерелаRanvier, Sylvain. "Radiowave propagation and antennas for high data rate mobile communications in the 60 GHz band." Nice, 2009. http://www.theses.fr/2009NICE4063.
Повний текст джерелаThe 60 GHz MIMO systems are seen as some of the best candidates for the implementation of future high data-rate short range communications systems such as wireless personal area networks (WPAN). Although the performance of MIMO systems has been studied thoroughly theoretically and experimentally at lower frequencies like at 2 and 5 GHz, there is a clear lack of measurement data and experimental performance evaluations of MIMO techniques at 60 GHz. Furthermore, more effort is still needed in the design and evaluation of compact low cost 60 GHz antennas for communication applications. In the first part of the thesis, the first 60 GHz MIMO channel measurement system is presented. It is based on a previously developed 2 and 5 GHz sounder and frequency converters. This system uses virtual antenna arrays to create the channel matrix. A measurement campaign is reported. In order to improve the delay resolution, two other MIMO measurement systems are presented, based on an ultra wide band (UWB) sounder and a vector network analyzer (VNA). Those systems allow full characterization of the MIMO channel in the delay and angular domains. In the second part of this work, the performance of multi-antenna techniques is evaluated based on the measurement data obtained in the first part of the thesis. Three of the most promising multi-antenna techniques, namely MIMO, antenna selection MIMO, and beam steering, are analyzed and compared. The presented results indicate that the mutual information of the measured MIMO channel is quite close to that of the independent and identically distributed (i. I. D. ) MIMO Rayleigh channel. Furthermore, in realistic conditions it is seen that MIMO-antenna selection often leads to lower mutual information than traditional MIMO with the same number of RF chains. Moreover, it is shown that when considering phase shifters with realistic losses, MIMO technique almost always outperforms beam steering technique. In the last part of the thesis a 60 GHz planar omnidirectional antenna is presented. This antenna is very suitable for communications applications since it has low profile and uses a metal layer only on one side of the substrate. Therefore, it can be manufactured easily and at very low cost. In addition, an advanced quasi full 3-D radiation pattern measurement system has been developed to evaluate probe-fed antennas. Very good measurement repeatability is reported. The radiation of the probe is analyzed and is seen to be the main limitation of the dynamic range of the measurement setup
Srivastava, Vikash Umeshchandra. "Smart Antennas & Power Management in Wireless Networks." Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/31244.
Повний текст джерелаMaster of Science
Bayram, Ahmet. "A Study of Indoor Ultra-wideband Propagation Measurement and Characterization." Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/32748.
Повний текст джерелаExtensive propagation data are collected in a frequency range of 1 to 12 GHz in two buildings on Virginia Tech campus. Using the data, channel characterization results are obtained and compared to those based on time-domain measurements. Some statistical results for small-scale fading, path loss exponent, and signal quality are presented. This comparison validates the accuracy of measured results for the UWB measurement campaign. The measured data also reaffirms the immunity of UWB propagation to small-scale fading which is present in narrowband wireless communication systems.
In addition to channel propagation measurements, signal distortions in UWB links, due to bandwidth limitations of antenna characteristics as well as the dispersive behavior of building materials, are also examined. In particular, the distortion of radiated signals by TEM horn antennas along off-boresight directions are studied experimentally. Furthermore, pulse distortions resulting from propagation through dispersive walls are demonstrated by simulation. The roles of receive-transmit antennas in a UWB link are examined, and the requirements for gain, input impedance, polarization, and phase of the radiated signal necessary for minimization of signal distortions are pointed out.
Master of Science
Bhat, Nitin. "An Antenna Specific Site Modeling Tool for Interactive Computation of Coverage Regions for Indoor Wireless Communication." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/31317.
Повний текст джерелаMaster of Science
Niang, Anna. "Antennes miniatures et structures électromagnétiques à circuits non-Foster." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS007/document.
Повний текст джерелаThe search of new materials has enabled new developments in recent decades. Among these are artificial or dielectric metamaterials. However, if these materials are passive, despite all the possible developments, the antennas performances or other structures resulting from them will still face the same fundamental limitations. By adding active circuits in these materials, such as negative resistors, negatives capacitors and negative inductors, it is possible to overcome these limitations and the synthesized properties and engineering applications can be significantly expanded. Indeed, this would create materials and devices with properties which can allow us to obtain behavior nonexistent in nature. This open the way to new applications. In this thesis, we explore the opportunity at first to use non-Foster circuits that are active feedback circuit, in the matching network of an electrically small antenna for low frequency operation. This helped to highlight its advantages over more conventional passive matching. Then, negative capacitors and negative and positive inductors were fabricated. Their totally different behaviors with passive components were also highlighted. This led us to apply them on periodic structures. Interesting results were obtained as superluminal wave propagation on a transmission line. And by applying to the unit cell of a metamaterial surface which is also a periodic structure, the size is reduced to a more compact cavity antennas designed for low frequency where the wavelength is very large
Issiali, Khouloud. "Study of smart antennas and MU-MIMO techniques for indoor radio engineering and planning tools." Thesis, Rennes, INSA, 2015. http://www.theses.fr/2015ISAR0039/document.
Повний текст джерелаThe deployment facility and flexibility of wireless technologies have allowed considerable evolution of IEEE 802 .11 standards. The arrival of the optical fiber to the home has further motivated the research studies to increase data rates and capacity. ln this context, the latest IEEE 802.l lac standard ratified in 2014 proposes new technologies to achieve maximum data rates above 1 Gbit/s. ln particular, 802.l lac includes the Multi-User Multiple Input Multiple Output (MU-MIMO) and Transmit Beamforming (TxBF). These smart antenna technologies assume a variable transmit antenna pattern in function of the users' position and the corresponding multipath propagation channel characteristics. However, the actual radio planning tools give a fixed coverage map in dependent of any adaptive or smart antenna processing. This thesis studies the impact of the MU-MIMO and TxBF techniques on radio engineering, system optimization as well as radio planning tools. Indeed, the first part of this thesis deals with refining the sum rate capacity gains by identifying interesting system configurations and optimal system parameters. The second part addresses the beamforming gains in terms of the Signal-to-Noise Ratio (SNR) gain and interference level to have realistic radio coverage modeling
LOPES, DANIEL T. "Caracterização de estruturas de ondas lentas helicoidais para utilização em, TWT de potência." reponame:Repositório Institucional do IPEN, 2007. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11596.
Повний текст джерелаMade available in DSpace on 2014-10-09T13:58:44Z (GMT). No. of bitstreams: 0
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
FAPESP:05/03612-0
Barksdale, Harry. "Millimeter wave scattering by rain in an antenna's near field." Diss., Virginia Polytechnic Institute and State University, 1988. http://hdl.handle.net/10919/53906.
Повний текст джерелаPh. D.
Alves, Thierry. "Conception d'antennes pour le réseau BAN et modélisation du canal de propagation." Phd thesis, Université Paris-Est, 2011. http://tel.archives-ouvertes.fr/tel-00664279.
Повний текст джерелаBellec, Mathilde. "Conception de systèmes antennaires omnidirectionnels et directifs favorisant les ondes de surface comme vecteur de propagation dans la bande HF." Thesis, Rennes 1, 2015. http://www.theses.fr/2015REN1S142.
Повний текст джерелаThe surface-waves propagate beyond the horizon. This phenomenon is an attractive feature for many applications operating in the HF band both in civil or military field. By example, we can quote the High Frequency Surface Waves Radar (HFSWR), communicating systems, or the study of the currentology. Currently, the antennas used in the field of surface-waves propagation are not fully optimized and radiate also in sky wave. In order to optimize the radiation pattern of the antennas used in these systems, the company TDF, the Direction Générale de l’Armement (DGA) and the Institute of Electronic and Telecommunications of Rennes (IETR) have proposed this projetct. The main objective of this work is to design electrically small antennas in the vertical plane (< 3 meters) in the HF band while reducing the radiation toward the sky. The first concept is based on vertically polarized antennas electrically small in the vertical plane coupled to horizontally radiators placed above the antenna. As a result, the radiation pattern in the horizontal plane is omnidirectional or directive with a radiation toward the sky reduced for the elevations range from -45° to +45°. Prototypes have been realized and validated by measurements. Then, in the second study we have developed antennas array in order to reduce the radiation toward the sky with another way that the horizontal radiators. This method allows reducing significantly the radiation toward the sky according to the number of elements in the array. Finally, in the third study we have studied electronically scanning antennas while maintaining the reduction of the radiation toward the sky. The first system is based on an array of radiator loaded by reactance, and the second is based on a planar array with an appropriate feeding
Adjali, Imad. "Approche statistique pour la quantification des performances d'antennes fortement couplées : application à la RFID dans le contexte d'une densité élevée de tags." Thesis, Paris Est, 2020. http://www.theses.fr/2020PESC2011.
Повний текст джерелаThis context of this thesis is that of UHF RFID use cases where a large number of RFID tags is concentrated in a limited volume. This context leads to scenarios in which the tag antennas can be strongly coupled electromagnetically. Under the conditions of high coupling and high density of tags, an antenna can be mismatched and its radiation pattern distorted. As a result of the antenna’s loss of performance, a global reduction of the tags reading rate can be observed as well as a drop of the reading distance for some of the tags. In order to tackle this highly random problem flowing from the unknown distribution of tags, the approach developed in this work is to assume that the electromagnetic coupling between antennas can be modeled by analytical formulas of self and mutual impedances valid for straight resonant dipoles. These dipoles can be loaded by complex impedances corresponding to the chip input impedances of real commercial RFID tags. The analytical models are validated by numerical simulations and experimental results. Statistical studies are performed for a large number of dipole distributions in terms of impedance mismatch and embedded gain variations in the direction of the reader. A statistical analysis of simulated commercial tags is also performed showing a good correlation with the dipole statistics. In the future, this work on the “group behavior” of antennas should provide the analysis and synthesis tools required for a robust evaluation of the tag performances in an environment characterized by a high tag density
Garcia, Pardo Concepción. "Experimental characterization of the radio channel for systems of large bandwidth and multiple antennas." Thesis, Lille 1, 2012. http://www.theses.fr/2012LIL10014/document.
Повний текст джерелаRecent and future wireless applications require large data rates. Multiple-Input Multiple-Output (MIMO) systems were proposed as one solution to achieve higher spectral efficiency. More recently Ultra-Wideband (UWB) systems, have gained interest owing its extremely high data rates. However, precise knowledge of the radio channel is an essential issue to design the global system and, thus to reach such improvement in the performances of wireless communications. This thesis is mainly focused on the experimental characterization of the radio channel for systems with large bandwidth and MIMO. In general, most of the research on MIMO and UWB are performed in indoor environments. However, there are other scenarios where reliable communications are also needed, for example, in tunnels. In this special environment, there is an increasing necessity of developing and implementing control/command equipment, in order to develop safe and efficient trains and infrastructures. Thus, the objectives pursued in this thesis are:- Improve an existing frequency-domain MIMO channel sounder to achieve more enhanced capabilities.- Develop a wideband time-domain MIMO channel sounder in order to perform measurements directly in the time-domain.- Characterize the MIMO-UWB radio channel in office environment by means of measurements carried out in the underground level of the Universidad Politécnica de Cartagena. Multi dimensional channel parameters have been deduced from numerous measurement campaigns.- Study the propagation in tunnels and give physical interpretation of the performances of space, frequency and polarization diversity, and of time reversal techniques
El, Masri Ihsan. "Caractérisation électromagnétique du canal de propagation sur silicium : applications aux interconnexions sans fils intra-puce pour les systèmes WiNoC Electromagnetic characterization of the intrachip propagation channel in Ka - and V -Bands, in IEEE Transactions on Components, Packaging and Manufacturing Technology 9 (10), October 2019." Thesis, Brest, 2019. http://www.theses.fr/2019BRES0060.
Повний текст джерелаIn the age of artificial intelligence, Big Data and the Internet of Things, the development of NoCs has become a priority. As part of the BBC project, we have opted for WiNoC interconnects, which provide efficient communication requirements at the intra-chip level (low latency, high throughput, minimal energy efficiency, compatibility with CMOS technology, adaptability for broadcast).This thesis focuses on the electromagnetic study the physical layer of WiNoC, and particularly on the characterization of propagation channels on silicon substrates.In this context, we highlight, through simulations and measurements in Ka and V bands, the problems of propagation in Si structures at very high frequency (cavities, surface waves and multiple paths).Subsequently, we propose a solution to limit these problems (due to reflections on the Si / Air interfaces) by adding an absorbing layer around the substrate. Using simulations and measurements in Q and V bands, we show improved transmission with a large bandwidth (>16 GHz).In order to reduce the size of the antennas and to increase the data rate, we study in the Sub-THz band, networks of monopoles embedded in a Si substrate placed between two metal plates.Finally, we estimate the performance and we show the possibility of transmitting at least 12 Gbps over a range of 21.2 mm and with an energy efficiency of the order of 4.5 pJ / bit. These results are comparable with competing solutions (WiNoC, RF interconnects, optical interconnects)
Farouq, Mohamed. "Transformation de front d'ondes par des méthodes matricielles." Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112222/document.
Повний текст джерелаThe characterization of electromagnetic radiation sources by near field techniques is now widely used. These involve measuring the radiated field close to the source to deduce, by mathematical processing, the field in other areas of space (near field and far field). There are many applications such as the evaluation of the antenna far field radiation patterns or the determination of safety perimeters around base station antennas. Furthermore, the near-field measurement technique can be used in the sources diagnostic.In our study, we present a new method for calculating the modal expansion coefficients from irregularly sampled or arbitrary measurement surfaces. The calculation of these modal coefficients allows the assessment of the radiation pattern of the antenna under test in every spatial directions.The principle of the matrix method is to calculate the modal coefficients by solving a system of linear equations relating the measured electric field and wave functions. Once the modal coefficients are known the far field of the structure is achieved.This method allows the separation between the geometry of the measuring surface and the coordinate system wherein the modal expansion is expressed. This leads to many advantages, such as selecting any measurement surfaces, for the reasons of compactness, implementation simplicity or truncation errors suppression
Forsberg, Nicklas, and Johan Säfholm. "Radioräckviddsberäkningar för flygande plattformar." Thesis, Linköping University, Department of Electrical Engineering, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-1080.
Повний текст джерелаThere exist several known methods for calculation of radio coverage for ground-based systems. As far as we know there are no equivalent methods for the case of flying platforms when the altitudes and speeds are significantly different to those of ground-based systems.
This thesis describes the theoretical concepts behind calculations of radio coverage for flying platforms. An investigation is made to sort out what is important and possible to employ in a model for simulations. A method is described and implemented in a program for evaluation of flying radio systems. Two typical cases of flight missions are simulated and discussed.
It is found that the free space model is valid most of the mission time. The contribution from the antennas is found to be small in comparison to the path loss. Further investigations suggested are e.g. better ground reflection models and a better model for the flight mechanics.
Mhedhbi, Meriem. "Contribution to deterministic simulation of Body area network channels in the context of group navigation and body motion analysis." Thesis, Rennes 1, 2015. http://www.theses.fr/2015REN1S049/document.
Повний текст джерелаRecent advances in wireless technologies and system, empowered by the miniaturization of devices, give rise to a new generation of Personal Area Networks allowing communications around the human body : Body Area networks. This thesis studies the Body Area Network channels in indoor environment in the context of motion analysis and group navigation. In this work a simulation approach for BAN channels is presented. The propagation channel simulator is based on ray tracing and the simulation approach is based on using perturbed antennas and the use of motion capture data for modelling the human mobility. Firstly, we investigate the antenna issue and the influence of the human body prox- imity on antenna radiation pattern. Besides, a simple model used to predict the antenna radiation pattern placed in proximity to a human body. Secondly, the physical sim- ulator is presented and the simulation approach is introduced. In order to check the proposed approach, preliminary simulations were carried out and a first comparison with available measurement data is made. Finally, a specific measurement campaign jointing radio data and motion capture data was exploited to validate and evaluate the simulation results
Vincent, Julien. "Modélisation d’antennes basses fréquences en présence de sol et d’environnements réalistes." Phd thesis, Toulouse, INPT, 2015. http://oatao.univ-toulouse.fr/14162/1/vincent.pdf.
Повний текст джерелаKouassi, Attibaud. "Propagation d'incertitudes en CEM. Application à l'analyse de fiabilité et de sensibilité de lignes de transmission et d'antennes." Thesis, Université Clermont Auvergne (2017-2020), 2017. http://www.theses.fr/2017CLFAC067/document.
Повний текст джерелаNowadays, most EMC analyzes of electronic or electrical devices are based on deterministic approaches for which the internal and external models’ parameters are supposed to be known and the uncertainties on models’ parameters are taken into account on the outputs by defining very large security margins. But, the disadvantage of such approaches is their conservative character and their limitation when dealing with the parameters’ uncertainties using appropriate stochastic modeling (via random variables, processes or fields) is required in agreement with the goal of the study. In the recent years, this probabilistic approach has been the subject of several researches in the EMC community. The work presented here is a contribution to these researches and has a dual purpose : (1) develop a probabilistic methodology and implement the associated numerical tools for the reliability and sensitivity analyzes of the electronic devices and systems, assuming stochastic modeling via random variables; (2) extend this study to stochastic modeling using random processes and random fields through a prospective analysis based on the resolution of the telegrapher equations (partial derivative equations) with random coefficients. The first mentioned probabilistic approach consists in computing the failure probability of an electronic device or system according to a given criteria and in determining the relative importance of each considered random parameter. The methods chosen for this purpose are adaptations to the EMC framework of methods developed in the structural mechanics community for uncertainty propagation studies. The failure probabilities computation is performed using two type of methods: the ones based on an approximation of the limit state function associated to the failure criteria, and the Monte Carlo methods based on the simulation of the model’s random variables and the statistical estimation of the target failure probabilities. In the case of the sensitivity analysis, a local approach and a global approach are retained. All these methods are firstly applied to academic EMC problems in order to illustrate their interest in the EMC field. Next, they are applied to transmission lines problems and antennas problems closer to reality. In the prospective analysis, more advanced resolution methods are proposed. They are based on spectral approaches requiring the polynomial chaos expansions and the Karhunen-Loève expansions of random processes and random fields considered in the models. Although the first numerical tests of these methods have been hopeful, they are not presented here because of lack of time for a complete analysis
Fuscaldo, Walter. "Advanced radiating systems based on leaky waves and nondiffracting waves." Thesis, Rennes 1, 2017. http://www.theses.fr/2017REN1S015/document.
Повний текст джерелаIn recent years, microwave, millimeter-wave, and THz applications such as medical and security imaging, wireless power transfer, and near-field focusing, just to mention but a few, have gained much attention in the area of ICT due to their potentially high social impact. On one hand, the need of highly-directive THz sensors with tunable radiating features in the far-field region has recently boosted the research activity in the design of flexible, low-cost and low-profile devices. On the other hand, it is of paramount importance to focus energy in the near-field region, and thus the generation of limited-diffraction waves in the microwave and millimeter-wave regime is a topic of recent increasing interest. In this context, leaky-wave theory is an elegant and extremely useful formalism which allows for describing in a common fashion guiding and radiating phenomena in both the near field and the far field, spanning frequencies from microwaves to optics passing through THz. In this PhD thesis we aim to exploit the intrinsic versatility of the leakywave approach to design advanced radiating systems for controlling the far-field radiating features at THz frequencies and for focusing electromagnetic radiation in the near field at millimeter waves. Specifically, the use of relatively new materials such as graphene and liquid crystals has been considered for the design of leaky-wave based radiators, achieving very promising results in terms of reconfigurability, efficiency, and radiating capabilities. In this context, an original theoretical analysis has provided new general formulas for the evaluation of the radiating features (e.g., half-power beamwidth, sidelobe level, etc.) of leaky-wave antennas. Indeed, the current formulations are based on several simplifying hypotheses which do not allow for an accurate evaluation of the beamwidth in different situations. In addition to the intriguing reconfigurable capabilities offered by leaky waves in far-field applications, interesting focusing capabilities can be obtained in the near field. In particular, it is shown that leaky waves can profitably be used to generate limited-diffraction Bessel beams by means of narrow-band radiators in the microwave range. Also, the use of higherorder leaky-wave modes allows for achieving almost the same performance in the millimeter-wave range, where previous designs were subjected to severe fabrication issues. Even more interestingly, the limited-diffractive character of Bessel beams can also be used to generate limited-diffraction pulses as superpositions of monochromatic Bessel beams over a considerable fractional bandwidth. In this context, a novel theoretical framework has been developed to understand the practical limitations to efficiently generate limited-diffraction, limited-dispersion pulses, such as X-waves, in the microwave/millimeter-wave range. As a result of this investigation, a class of wideband radiators has been thoroughly analyzed, showing promising capabilities for the generation of both zeroth-order and higher-order Xwaves. The latter may pave the way for the first localized transmission of orbital angular momentum in the microwave range
Zemba, Michael J. "Site Characterization of Phase Instability via Interferometer Measurement." University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1383565461.
Повний текст джерелаPanahandeh, Ali. "Multi-polarized sensing for cognitive radio." Doctoral thesis, Universite Libre de Bruxelles, 2012. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209586.
Повний текст джерелаFirst the depolarization occurring in the wireless channel is studied for two cognitive radio scenarios. This is done through an extensive measurement campaign in two outdoor-to-indoor and indoor-to-indoor scenarios where the parameters characterizing the radiowaves polarization are characterized at three different spatial scales: small-scale variation, large-scale variation and distance variation.
Second, a new approach is proposed in modeling of multi-polarized channels. The polarization of received fields is characterized from an electromagnetic point of view by modeling the polarization ellipse. Theoretical formulations are proposed in order to obtain the parameters characterizing the polarization ellipse based on the signals received on three cross-polarized antennas. A system-based statistical model of the time-dynamics of polarization is proposed based on an indoor-to-indoor measurement campaign. The analytical formulations needed in order to project the polarization ellipse onto a polarized multi-antenna system are given and it is shown how the model can be generated.
Third, the impact of polarization on the spectrum sensing performances of energy detection method is presented and its importance is highlighted. The performance of spectrum sensing with multi-polarized antennas is compared with unipolar single and multi-antenna systems. This analysis is based on an analytical formulation applied to the results obtained from the multi-polarized measurement campaign. The detection probability as a function of distance between the primary transmitter and the secondary terminal and the inter-antenna correlation effect on the spectrum sensing performance are studied.
An important limitation of energy detector is its dependence on the knowledge of the noise variance. An uncertainty on the estimation of the noise variance considerably affects the performance of energy detector. This limitation is resolved by proposing new multi-polarized spectrum sensing methods which do not require any knowledge neither on the primary signal nor on the noise variance. These methods, referred to as “Blind spectrum sensing methods”, are based on the use of three cross-polarized antennas at the secondary terminal. Based on an analytical formulation and the results obtained from the measurement campaign, the performances of the proposed methods are compared with each-other and with the energy detection method. The effect of antenna orientation on the spectrum sensing performance of the proposed methods and the energy detection method is studied using the proposed elliptical polarization model.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished
Narrainen, Jessen. "Perforance evaluation of vehicle radiofrequency communication systems : contribution to the modelling approach." Thesis, Rennes, INSA, 2017. http://www.theses.fr/2017ISAR0007/document.
Повний текст джерелаThe general framework of this Ph.D. thesis deals with Vehicle to Vehicle (V2V) communications. This communication is principally dedicated to reinforce security through exchange of information between vehicles in case of unexpected events. The development of V2V solutions requires the understanding and merging of a number of techniques from several communication technology areas. Indeed, the performance of these systems are related to three main blocks: the implementation of the modems, the antenna configuration and the fast varying electromagnetic environment surrounding the transmitter and the receiver. The purpose of this PhD thesis is precisely to elaborate a design strategy to investigate all the different blocks constituting the communication chain. The ultimate goal is to optimize antenna selection and location on board the vehicle. In the first place, we proposed a geometry-based stochastic channel modelling approach to develop virtual dynamic scenarios. It was shown that the most common propagation environments such as rural, highway or urban-like propagation channels are reached through adjustment or numbers and location of simple metallic plates. Using this method, we are able to emulate the characteristics, such as the delay spread, angles of arrival distribution and the Doppler spectrum, of these typical driving scenarios. Moreover, we dealt with antenna integration problems in the second part of this work. A study on the simplification of numerical models of vehicles was carried out. Furthermore in this section, we investigated the limit of validity of representing the integrated antenna on board vehicle solely by its radiation pattern. We deduced from this study that the interactions with the elements present in the near-field is no longer valid. Thus, a strategy to alleviate the degree of error was found upon consideration of the near-field scatter in the a-priori simulation of the antenna integrated on the vehicle. In the third part of this thesis, we evaluated the performance of different antenna configurations in terms of packet error rate after the embodiment of the PHY layer of the LEEE 802.11p standard. Simulation results, for each antenna configurations, was given for several combinations of PHY layer parameters such as data rate and packet length. The last part of this manuscript is dedicated to the presentation of a measurement campaign that was carried out in a rural driving environment. Results obtained from these functional tests were confronted with simulation results to demonstrate the strength of the latter. We found that the expected trends in communication performance in terms of PER are globally predictable from our model though we obtained surprising results in some cases, needing further investigation
Donzelli, Valderez de Almeida. "Polarização elíptica: influência no desempenho de cobertura da TV digital." Universidade Presbiteriana Mackenzie, 2011. http://tede.mackenzie.br/jspui/handle/tede/2748.
Повний текст джерелаCoordenação de Aperfeiçoamento de Pessoal de Nível Superior
The technology environment in the broadcast area using analog technology was defined and did not offer a great research interest, in specific topics related to development of the transmitting antenna for broadcast television. With the implementation of the transmission system employing digital technology, which adds as main news the possibility of mobility and portability of the receiving system, the interest in studies and researches returned, showing one of the main themes to be developed using circular polarization or elliptical compared with horizontal polarization, that was most used by broadcasters. Given this new scenario and the need for evaluation by a scientific methodology of the radiating system in the transmission station performance, goals were established that define the scope for this research: to analyze the influence of the radiating system depending on the desired coverage area and the reception possibilities internal fixed , external fixed, portable and mobile, considering the diversity specific propagation environment of the region studied due to topographical and environmental condition. The criteria to be used will be the theoretical propagation prediction and field survey of the signals received which will provide data for the analysis of variables that influence the behavior of the transmission system, considering the location and technical characteristics of the main transmission station installation and different polarization of the radiating system configurations in horizontal, vertical and elliptical.
O cenário tecnológico na área de transmissão empregando tecnologia analógica estava bem segmentado e não oferecia um ambiente de grande interesse em pesquisas específicas para desenvolvimentos de temas relacionados a antena de transmissão para televisão aberta. Com a implantação do sistema de transmissão empregando a tecnologia digital, que agrega como principal novidade a possibilidade de mobilidade e portabilidade do sistema de recepção , o interesse nos estudos e pesquisas retomou, apresentando como um dos principais temas a serem desenvolvidos a utilização de polarização circular ou elíptica comparada com a polarização horizontal, que era a mais utilizada pela emissoras. Tendo em vista este novo cenário e a necessidade de avaliação por meio de uma metodologia científica do comportamento do sistema irradiante de transmissão no resultado no desempenho da estação transmissora, foram estabelecidas as metas que definem o escopo para este trabalho: analisar a influência do tipo de sistema irradiante em função da área de cobertura desejada e das possibilidades de recepção fixa interna, fixa externa, portátil e móvel, frente às diversidades específicas do ambiente de propagação da região estudada devido às condições topográficas e ambientais. Os critérios a serem empregados serão os teóricos de predição de propagação e prático de levantamento de campo dos sinais recebidos os quais irão fornecer dados para a análise das variáveis que influenciam no comportamento do sistema de transmissão, considerando o local e as características técnicas de instalação da estação de transmissão principal e variando a polarização do sistema irradiante nas configurações horizontal, vertical e elíptica.
Chiu, Cheng-Wei, and 邱振瑋. "A Study on Antennas and Wave Propagation for Packaging RFID." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/06174501738167458200.
Повний текст джерела國立臺灣科技大學
電機工程系
93
This thesis studies the antenna and wave propagation properties of the radio frequency identification (RFID) for packaging objects. A finite difference time domain software package XFDTD and a finite element software package HFSS are applied in this study. Particularly, a tag antenna for Alien RFID IC is designed and some parameters to control the properties of the tag antenna are evaluated. Also, measurements of the properties and the readable distance of the tag antenna are performed in NTUST Antenna Far-field Anechoic Chamber to verify the performance of the tag antenna design. On the other hand, contains in packages will influence tag antenna and wave propagation properties significantly. Although different antenna designs may be employed for specific applications, wave propagation through stacked packages is usually a difficult problem. Thus, the efficiency of the packaging RFID system may be affected. To solve this problem, a practical method for the antenna design and wave propagation in stacked packages has been studied. Patent applications are submitted for the results developed in this study.
Chun, Chen Yen, and 陳彥君. "Broadband Antennas Design and Applications - Propagation Property with Various Mediums." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/11811079450004683975.
Повний текст джерела大葉大學
電信工程學系碩士班
94
For recognizing the EM characteristics of mediums, the simulation is developed in this thesis. Using the simulated results of S parameters, the dielectric constant and loss tangent of medium can be calculated by EM formulas. Generally, the transmitting antennas in test ranges are consist of various narrow band antennas for wide band applications. The drawback are higher cost for purchasing the probe antennas, time consuming for changing and uncertainty of the antenna patterns; therefore, a novel transmitter antenna constructed with low directivity wideband horn and wideband balun will be developed in this thesis and applied for the Near-field antenna measurement system. The operating frequency from 1 GHz to 18 GHz, low directivity and symmetry antenna pattern are achieved. Meanwhile, a ultra-wideband bow-tie receiving antenna is designed and applied in the water from 3GHz to 12.5 GHz. Both S-parameters and radiation patterns are measured by the network analyzer and impulse time domain antenna measurement system respectively. The EM wave propagation for various media is analyzed
Jiang, Hong Sheng, and 江宏昇. "Simulation and measurement for indoor propagation using diversity monopole antennas." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/40644828691505988502.
Повний текст джерелаMerola, Christopher S. "Resonant Antennas Based on Coupled Transmission-Line Metamaterials." 2011. https://scholarworks.umass.edu/theses/629.
Повний текст джерелаGutierrez, Felix active 2013. "Millimeter-wave and sub-terahertz on-chip antennas, arrays, propagation, and radiation pattern measurements." 2013. http://hdl.handle.net/2152/23109.
Повний текст джерелаtext
Hailu, Daniel. "Hybrid Spectral Ray Tracing Method for Multi-scale Millimeter-wave and Photonic Propagation Problems." Thesis, 2011. http://hdl.handle.net/10012/6355.
Повний текст джерелаZuniga, Barahona Christian David. "Channel modeling of an antenna plasma-plume system." Thesis, 2005. http://hdl.handle.net/2152/2382.
Повний текст джерелаWong, Alex H. C. "Antenna Selection and Deployment Strategies for Indoor Wireless Communication Systems." 2007. http://hdl.handle.net/2292/432.
Повний текст джерела(7478276), Vladlen Alexandrovich Podolsky. "INVESTIGATION OF PLASMAS SUSTAINED BY HIGH REPETITION RATE SHORT PULSES WITH APPLICATIONS TO LOW NOISE PLASMA ANTENNAS." Thesis, 2019.
Знайти повний текст джерелаIn the past two decades, great interest in weakly ionized plasmas sustained by high voltage nanosecond pulsed plasmas at high repetition rates has emerged. For such plasmas, the electron number density does not significantly decay between pulses, unlike the electron temperature. Such conditions are favorable to reconfigurable plasma antennas where the low electron temperature may enable the reduction of the Johnson–Nyquist thermal noise if an antenna is operated in the plasma afterglow. Moreover, it may be possible to sustain such conditions with RF pulses. Doing so could enable a plasma antenna that transmits the driving frequency when the pulse is applied and receives other frequencies with low thermal noise between pulses.
To study nanosecond pulsed plasmas, experiments were performed in a parallel-plate electrode configuration in argon and nitrogen gas at a pressure of several Torr and repetition frequencies of 30-75 kHz. To measure the time-resolved electron number density in the afterglow of each pulse, a custom 58.1 GHz homodyne microwave interferometer was constructed. The voltage and current measurements were made using a back current shunt (BCS). Initial analysis of the measured electron density in both plasmas indicated that the electron thermalization was much faster than the electron decay. In the nitrogen plasma, dissociative recombination with cluster ions was the dominant electron loss mechanism. However, the dissociative recombination rates of the electrons in the argon plasma suggested the presence of molecular impurities, such as water vapor. Therefore, to better understand the recombination mechanisms in argon plasma with trace amounts (0.1% or less by volume) of water vapor under the experimental conditions, a 0-D kinetic model was developed and fit to the experimental data. The influence of trace amounts of water on the electron temperature and density decay was studied by solving electron energy and continuity equations. It was found that in pure argon, Ar+ ions dominate while the electrons are very slow to thermalize and recombine. Including trace amounts of water impurities drastically reduces the time for electrons to thermalize and increases their rate of recombination.
In addition to large quasi-steady electron number densities and low electron temperature in the plasma afterglow, plasmas sustained by nanosecond pulses use a lower power budget than those sustained by RF or DC supplies. The efficiency of the power budget can be characterized by measuring the ionization cost per electron, defined as the ratio of the energy deposited in a pulse to the total number of electrons created. This was experimentally determined in air and argon plasmas at 2-10 Torr sustained by 1-7 kV nanosecond pulses at repetition frequencies of 0.1-30 kHz. The number of electrons were determined from the measured electron density through microwave interferometry and assuming a plasma volume equivalent to the volume between electrodes. The energy deposited was calculated from voltage and current measurements using both a BCS as well as high frequency resistive voltage divider and fast current transformer (FCT). It was found that the ionization cost in all conditions was within a factor of three of Stoletov’s point (the theoretical minimum ionization cost) and two orders of magnitude less than RF plasma.
Having shown that it is possible to
generate high electron density, low electron temperature plasmas with
nanosecond pulses, it was necessary to now create a plasma antenna prototype.
Initially, commercial fluorescent light bulbs were used and ignited using
surface wave excitation at various RF frequencies and powers. The S11
of the antenna response was measured by a VNA through a novel coupling circuit,
while the deposited power was measured using a bi-directional coupler. Next, a
custom plasma antenna was created in which the pressure and gas composition
could be varied. In addition to the S11 and deposited power, the
antenna gain, and the electron number density were also measured for a pure
argon plasma antenna at pressures of 0.3-1 Torr. Varying the applied power shifts
the antenna resonance frequency while increasing the excitation frequency
caused an increase in measured electron density for the same deposited power.
Initial tests using direct electrode excitation of a twin-tube integrated
compact fluorescent light bulb with nanosecond pulses have successfully been
achieved. Future efforts include designing the proper circuitry to time-gate
out the large pulse voltage to facilitate safe antenna measurements in the
plasma afterglow.
Hussain, Intikhab. "Channel modelling and analysis of Wits mock-mine with different antenna parameters." Thesis, 2017. http://hdl.handle.net/10539/23519.
Повний текст джерелаIn the mining industry, communications systems are important for ensuring personnel safety and optimizing the mining processes underground. Achieving robust and reliable through-the-air (TTA) communication systems has always been a challenge in the underground mining environment due to harsh and dynamic conditions. TTA requires radio channel characterization for efficient designing and deploying of the communications systems. The literature covers the statistical radio propagation of a room and pillar coal mine, a longwall coal mine, CANMET Gold mine, Camborne School of Mines hard rock mine tunnel, MUZ Coal mine, an iron-ore mine and a lead-zinc mine with linearly polarized antennas at different frequencies. [Abbreviated Abstract. Open document to view full version]
MT 2017