Dissertations / Theses on the topic 'Antenna models'
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Su, Tao. "Characterization of antenna radiation and receiving properties in complex environments based on physical models." Access restricted to users with UT Austin EID Full text (PDF) from UMI/Dissertation Abstracts International, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3023561.
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Shekhar, Hemabh. "Multi-antenna physical layer models for wireless network design." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/22681.
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Thesis (Ph. D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2008.Committee Chair: Ingram, Mary Ann; Committee Member: Andrew, Alfred; Committee Member: Copeland, John; Committee Member: Owen, Henry; Committee Member: Sivakumar, Raghupathy.
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Licul, Stanislav. "Ultra-Wideband Antenna Characterization and Modeling." Diss., Virginia Tech, 2004. http://hdl.handle.net/10919/29487.
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A new methodology is presented for characterizing an antenna system both in the time and frequency domain with one set of parameters using a singularity expansion method representation. A minimal set of parameter modeling antenna systems using the Matrix-Pencil method has been demonstrated. It has been shown that it is possible to obtain frequency-domain patterns from pole/residue models of antenna realized effective length. Thus, a pole/residue model of the antenna realized effective length presents a complete description in both the time and frequency domains. Once such a model is available, one can obtain the antenna pattern, directivity and gain in the frequency domain and the radiated transient waveform for an arbitrary excitation waveform and an arbitrary antenna orientation.Ph. D.
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Cracraft, Michael Andrew. "Mobile array designs with ANSERLIN antennas and efficient, wide-band PEEC models for interconnect and power distribution network analysis." Diss., Rolla, Mo. : University of Missouri-Rolla, 2007. http://scholarsmine.umr.edu/thesis/pdf/mcthesis20070623_09007dcc80374999.pdf.
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Thesis (Ph. D.)--University of Missouri--Rolla, 2007.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed November 16, 2007) Includes bibliographical references (p. 134-136).
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Bengtsson, Mats. "Antenna array signal processing for high rank data models." Doctoral thesis, KTH, Signaler, sensorer och system, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-2903.
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Grimm, Markus [Verfasser]. "Analytic on-body antenna and propagation models / Markus Grimm." Hannover : Gottfried Wilhelm Leibniz Universität Hannover, 2019. http://d-nb.info/1176105191/34.
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Glenn, Dickins, and glenn dickins@dolby com. "Applications of Continuous Spatial Models in Multiple Antenna Signal Processing." The Australian National University. Research School of Information Sciences and Engineering, 2008. http://thesis.anu.edu.au./public/adt-ANU20080702.222814.
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This thesis covers the investigation and application of continuous spatial models for multiple antenna signal processing. The use of antenna arrays for advanced sensing and communications systems has been facilitated by the rapid increase in the capabilities of digital signal processing systems. The wireless communications channel will vary across space as different signal paths from the same source combine and interfere. This creates a level of spatial diversity that can be exploited to improve the robustness and overall capacity of the wireless channel. Conventional approaches to using spatial diversity have centered on smart, adaptive antennas and spatial beam forming. Recently, the more general theory of multiple input, multiple output (MIMO) systems has been developed to utilise the independent spatial communication modes offered in a scattering environment.¶
Underlying any multiple antenna system is the basic physics of electromagnetic wave propagation. Whilst a MIMO system may present a set of discrete inputs and outputs, each antenna element must interact with the underlying continuous spatial field. Since an electromagnetic disturbance will propagate through space, the field at different positions in the space will be interrelated. In this way, each position in the field cannot assume an arbitrary independent value and the nature of wave propagation places a constraint on the allowable complexity of a wave-field over space. To take advantage of this underlying physical constraint, it is necessary to have a model that incorporates the continuous nature of the spatial wave-field. ¶This thesis investigates continuous spatial models for the wave-field. The wave equation constraint is introduced by considering a natural basis expansion for the space of physically valid wave-fields. This approach demonstrates that a wave-field over a finite spatial region has an effective finite dimensionality. The optimal basis for representing such a field is dependent on the shape of the region of interest and the angular power distribution of the incident field. By applying the continuous spatial model to the problem of direction of arrival estimation, it is shown that the spatial region occupied by the receiver places a fundamental limit on the number and accuracy with which sources can be resolved. Continuous spatial models also provide a parsimonious representation for modelling the spatial communications channel independent of specific antenna array configurations. The continuous spatial model is also applied to consider limits to the problem of wireless source direction and range localisation.
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Herring, Keith 1981. "Propagation models for multiple-antenna systems : methodology, measurements and statistics." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/43027.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2008.Includes bibliographical references (leaves 219-223).
The trend in wireless communications is towards utilization of multiple antenna systems. While techniques such as beam-forming and spatial diversity have been implemented for some time, the emergence of Multiple-Input Multiple-Output (MIMO) communications has increased commercial interest and development in multiple-antenna technology. Given this trend it has become increasingly important that we understand the propagation characteristics of the environments where this new technology will be deployed. In particular the development of low-cost, high-performance system architectures and protocols is largely dependent on the accuracy of available channel models for approximating realized propagation behavior. The first contribution of this thesis is a methodology for the modeling of wireless propagation in multiple antenna systems. Specifically we consider the problem of propagation modeling from the perspective of the protocol designer and system engineer. By defining the wireless channel as the complex narrow-band channel response h e C between two devices, we characterize the important degrees of freedom associated with the channel by modeling it as a function of its path-loss, multipath/frequency, time stability, spatial, and polarization characteristics. We then motivate this model by presenting a general set of design decisions that depend on these parameters such as network density, channel allocation, and channel-state information (CSI) update rate. Lastly we provide a parametrization of the environment into measurable factors that can be used to predict channel behavior including link-length, Line-Of-Sight (LOS), link topology (e.g. air-to-ground), building density, and other physical parameters. The second contribution of this thesis is the experimental analysis and development of this modeling space.
(cont) Specifically we have gathered a large database of real wireless channel data from a diverse set of propagation environments. A mobile channel-data collection system was built for obtaining the required data which includes an eight-channel software receiver and a collection of WiFi channel sounders. The software receiver synchronously samples the 20-MHz band centered at 2.4 GHz from eight configurable antennas. Measurements have been carried out for both air-to-ground and ground-to-ground links for distances ranging from tens of meters to several kilometers throughout the city of Cambridge, MA. Here we have developed a collection of models for predicting channel behavior, including a model for estimating the path-loss coefficient a in street environments that utilizes two physical parameters: P1 = percentage of building gaps averaged over each side of the street, P2= percentage of the street length that has a building gap on at least one side of the street. Results show a linear increase in a of 0.53 and 0.32 per 10% increase in P1 and P2, respectively, with RMS errors of 0.47 and 0.27 a for a's between 2 and 5. Experiments indicate a 10dB performance advantage in estimating path-loss with this multi-factor model over the optimal linear estimator (upper-bound empirical model) for link lengths as short as 100 meters. In contrast, air-to-ground links have been shown to exhibit log-normal fading with an average attenuation of a ; 2 and standard deviation of 8dB. Additionally we provide exhaustive evidence that the small-scale fading behavior (frequency domain) of both Non-Line-Of-Sight (NLOS) air-to-ground and ground-to-ground links as short as tens of meters is Rayleigh distributed. More specifically, fading distributions across a diverse set of environments and link lengths have been shown to have Rician K-factors smaller than 1, suggesting robust performance of the Rayleigh model.
(cont) A model is also presented that defines a stochastic distribution for the delay-spread of the channel as a function of the link-length (do), multipath component (MPC) decay-rate ( ... attenuation per unit delay ... ), and MPC arrival-rate (q = MPCs per unit delay ... periments support the use of this model over a spectrum of link-lengths (50m-700m) and indicate a dense arrival-rate (q) (on the order of 1 MPC) in ground-to-ground links. In this range the frequency structure of the channel is insensitive to q, which reduces the modeling complexity to a single unknown parameter, P. We provide estimators for 3 over a variety of environment types that have been shown to closely replicate the fade width distribution in these environments. The observed time-coherence length (tc) of MPCs tend to be either less than 300ms (high-frequency) or 5 seconds and longer (low-frequency), resulting in a Rician-like distribution for fading in the time domain. We show that the time characteristics of the channel are accurately modeled as the superposition of two independent circularly symmetric complex gaussian random variables corresponding to the channel response due to a set of stable and unstable MPCs. We observe the S-factor, defined as the ratio of average power in stable to unstable MPCs (distinct from the Rician K-factor), which ranges between 0-30dB depending on environment and link length, and can be estimated with an rms error of 3dB in both ground-to-ground and air-to-ground link regimes. Experiments show improved performance of this model over the Rician fading model which has been shown to underestimate high fade events (tails) in the time domain, corresponding to cases where the stable MPCs destructively combine to form a null. Additionally, the Kronecker MIMO channel model is shown to predict channel capacity (of a 7x7 system) with an rms error of 1.7 ... (at 20dB SNR) over a diverse set of observed outdoor environments.
(cont) Experiments indicate a 3dB performance advantage in this prediction when applied to environments that are not dominated by single-bounce propagation paths (Single-bounce: 2.1 ... rms, Multi-bounce: 1 ... rms).
by Keith T. Herring.
Ph.D.
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Sherkat, Navid. "Approximation of Antenna Patterns With Gaussian Beams in Wave Propagation Models." Thesis, Linnéuniversitetet, Institutionen för datavetenskap, fysik och matematik, DFM, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-14437.
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The topic of antenna pattern synthesis, in the context of beam shaping, is considered. One approach to this problem is to use the method of point matching. This method can be used to approximate antenna patterns with a set of uniformly spaced sources with suitable directivities. One specifies a desired antenna pattern and approximates it with a combination of beams. This approach results in a linear system of equations that can be solved for a set of beam coefficients. With suitable shifts between the matching points and between the source points, a good agreement between the assumed and the reproduced antenna patterns can be obtained along an observation line. This antenna modelling could be used in the program NERO to compute the field at the receiver antenna for a realistic 2D communication link. It is verified that the final result is not affected by the details of the antenna modelling.
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Papou, Uladzislau. "Conformal and reconfigurable sparse metasurfaces : advanced analytical models and antenna applications." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASC027.
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Cette thèse de doctorat traite des métasurfaces constituées de diffuseurs sub-longueur d’onde conçus pour contrôler les fronts d’ondes électromagnétiques. Elle introduit des modèles analytiques et numériques inédits qui résolvent le problème de diffusion inverse en tenant compte des interactions entre éléments de la métasurface. Le manuscrit se concentre plus particulièrement sur des réseaux, périodiques ou non, de fils structurés, permettant la réalisation d’antennes reconfigurables électroniquement. Le manuscrit est divisé en deux grandes parties, l’une sur des arrangements périodiques de fils appelés métaréseaux et l’autre sur des métasurfaces éparses sans caractère périodique. Dans les deux cas, des réalisations expérimentales dans le domaine microondes viennent appuyer les développements théoriques. Dans la première partie, les conditions théoriques conduisant à un contrôle total des ordres de diffraction rayonnés par des métaréseaux, dont la période est composée de plusieurs fils structurés individuellement, sont établies et l’importance du contrôle du champ proche est alors soulignée. Par ailleurs, une expression analytique des paramètres effectifs des fils, s’appuyant sur une simulation numérique, a également été établie. Il devient ainsi possible d’exploiter des géométries quelconques pour des métaréseaux fonctionnant dans les domaines allant des microondes à l’optique. Dans la deuxième partie de la thèse, le modèle analytique des métaréseaux, réservé aux distributions périodiques planes, est généralisé aux distributions non périodiques de fils disposés sur des surfaces quelconques en s’appuyant sur le calcul de la fonction de Green. Ce concept est appliqué à des métasurfaces éparses intervenant dans une cavité Fabry-Perot ou dans une antenne semi-cylindrique. Enfin, la démarche est utilisée pour concevoir une métasurface éparse plane reconfigurable. Un prototype a été réalisé et utilisé pour démontrer expérimentalement le contrôle dynamique de l’onde, en champ lointain et en champ proche, via des applications telles que le dépointage de faisceau, la création de faisceaux multiples ou encore la focalisation au-delà de la limite de diffractionThis PhD thesis deals with electromagnetic metasurfaces for wavefront manipulation represented by arrays of scatterers engineered at subwavelength scale. The manuscript develops novel analytical and numerical models that allow one to solve the inverse scattering problem by taking into account all interactions between elements of a metasurface. Specifically, the manuscript focuses on sparse arrays, periodic or not, of structured wires for the application to electronically reconfigurable antennas. The manuscript is divided into two main parts, one on periodic arrangements of wires called metagratings and one on sparse metasurfaces when there is no periodicity imposed. Each part is endorsed by experiments performed at microwave frequencies. In the first part, theoretical conditions for arbitrary control of the diffraction patterns with metagratings, whose period is composed of multiple individually-engineered wires, are established and importance of the near-field regulation is highlighted. Moreover, an analytical retrieval technique is developed and allows one to consider, with the help of full-wave simulations, arbitrarily structured wires for metagratings operating from microwave to optical domains. In the second part of the thesis, the analytical model of metagratings is generalized, from planar periodic, to arbitrarily-shaped non-periodic distributions of wires by means of numerical calculation of a Green’s function. The concept is applied to design sparse metasurfaces in Fabry-Perot cavity and semi-cylindrical antenna configurations. Finally, the approach is applied to design a reconfigurable planar sparse metasurface. A fabricated sample is exploited to experimentally demonstrate dynamic control of the far-field radiation pattern and the near-field intensity distribution. As such beam-steering, multi-beam manipulation and subdiffraction focusing are shown
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Lyberopoulos, George L. "Numerical models of new HF shipboard communication antenna systems for improved survivability." Thesis, Monterey, California: U.S. Naval Postgraduate School, 1986. http://hdl.handle.net/10945/22007.
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Takamizawa, Koichiro. "Analysis of Highly Coupled Wideband Antenna Arrays Using Scattering Parameter Network Models." Diss., Virginia Tech, 2002. http://hdl.handle.net/10919/11099.
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Wideband phased arrays require very tight element spacing to permit wide angle scanning of the main beam over the wide bandwidth. The consequence of tight spacing is very high mutual coupling among the elements in the array. Previous efforts by Virginia Tech Antenna Group has shown that the strong coupling can be utilized in arrays to obtain broadband frequency response while maintaining a small element spacing. However, mutual coupling between elements in a tightly coupled array can sometimes dramatically change the operating frequency, bandwidth, and radiation pattern from that of the single isolated element. Thus, there are some fundamental questions that remain regarding the effective operation of highly coupled arrays for beam forming, beam scanning, and aperture reconfiguration. Existing antenna pattern analysis techniques including the active element pattern method are inadequate for the application in highly coupled arrays.
This dissertation focuses on the development of a new antenna array analysis technique. The presented method is based on the scattering parameter network descriptions of the array elements, associated feed network and the active element patterns. The developed model is general. It can be applied to an array of any size and configuration. The model can be utilized to determine directivity, gain and realized gain of arrays as well as their radiation efficiency and impedance mismatch. Using the network model, the relationship between radiation pattern characteristics and the input impedance characteristics of the array antennas becomes clear. Three types of source impedance matching conditions for array antennas are investigated using the model. A numerically simulated array of strip dipole array is used to investigate the effects of various impedance matching methods on the radiation pattern and impedance bandwidth. An application of network analysis is presented on an experimental investigation of $3\times 3$ Foursquare array test bed to further verify the concepts.Ph. D.
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Choi, Il Yong. "Design of survivable shipboard HF mast antenna models using the numerical electromagnetics code." Thesis, Monterey, California: U.S. Naval Postgraduate School, 1987. http://hdl.handle.net/10945/22739.
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He, Xin, and 何鑫. "Probabilistic quality-of-service constrained robust transceiver designin multiple antenna systems." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B48199527.
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In downlink multi-user multiple-input multiple-output (MU-MIMO)
systems, different users, even multiple data streams serving one user,
might require different quality-of-services (QoS). The transceiver should
allocate resources to different users aiming at satisfying their QoS
requirements. In order to design the optimal transceiver, channel
state information is necessary. In practice, channel state information
has to to be estimated, and estimation error is unavoidable. Therefore,
robust transceiver design, which takes the channel estimation
uncertainty into consideration, is important. For the previous robust
transceiver designs, bounded estimation errors or Gaussian estimation
errors were assumed. However, if there exists unknown distributed interference,
the distribution of the channel estimation error cannot be
modeled accurately a priori. Therefore, in this thesis, we investigate
the robust transceiver design problem in downlink MU-MIMO system
under probabilistic QoS constraints with arbitrary distributed channel
estimation error.
To tackle the probabilistic QoS constraints under arbitrary distributed
channel estimation error, the transceiver design problem is expressed
in terms of worst-case probabilistic constraints. Two methods are
then proposed to solve the worst-case problem. Firstly, the Chebyshev
inequality based method is proposed. After the worst-case probabilistic
constraint is approximated by the Chebyshev inequality, an
iteration between two convex subproblems is proposed to solve the
approximated problem. The convergence of the iterative method is
proved, the implementation issues and the computational complexity
are discussed.
Secondly, in order to solve the worst-case probabilistic constraint more
accurately, a novel duality method is proposed. After a series of reformulations
based on duality and S-Lemma, the worst-case statistically
constrained problem is transformed into a deterministic finite
constrained problem, with strong duality guaranteed. The resulting
problem is then solved by a convergence-guaranteed iteration between
two subproblems. Although one of the subproblems is still nonconvex,
it can be solved by a tight semidefinite relaxation (SDR).
Simulation results show that, compared to the non-robust method, the
QoS requirement is satisfied by both proposed algorithms. Furthermore,
among the two proposed methods, the duality method shows a
superior performance in transmit power, while the Chebyshev method
demonstrates a lower computational complexity.published_or_final_version
Electrical and Electronic Engineering
Master
Master of Philosophy
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Sonkki, M. (Marko). "Wideband and multi-element antennas for mobile applications." Doctoral thesis, Oulun yliopisto, 2013. http://urn.fi/urn:isbn:9789526201085.
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Abstract This dissertation presents wideband and multi-element antennas for mobile applications. It is divided into the following main parts: modal theory, wideband antennas, multi-element antennas, and wideband multi-element antennas. The radiating fields are first studied in terms of spherical scalar and vector modes, and it is shown how these modes correlate with the characteristic current modes on a planar mobile ground plane. The theory part shows how it is possible to excite the same modes on a conventional sphere and a rectangular planar mobile ground plane. The theory refers to the novel wideband antenna structures presented in this dissertation, in terms of current and radiating modes. After studying the modes, the dissertation shows how to excite a radiating antenna mode within a wide frequency bandwidth. To gain this, two main approaches are taken. First, a quasi-complementary antenna (QCA) structure with an electric conductor and magnetic slot is presented, and its characteristics are studied. A QCA UWB antenna, and a QCA element excited with a monopole or a dipole, is presented. The QCA structure compensates for the imaginary part of the input impedance on wide frequency bandwidth, when, at the same time, the fundamental mode is excited to ensure good radiating properties. The second approach uses a symmetrical feeding with two antenna elements to gain a wide frequency bandwidth, the relative -6 dB impedance bandwidth between 37.5–80%. When a field is symmetrically coupled to the conducting ground plane, the excitation avoids the awakening of higher order modes which might disturb the performance of the antenna. It is also shown, by using multiple feeding elements, that the excitation of orthogonal higher order modes on a small radiating ground plane is possible. As the modes are orthogonal to each other, they present a very low correlation. By using this kind of approach, radiation pattern diversity can be obtained in mobile applications within a small volume. On the other hand, when combining two QCA elements to a one multi-element antenna structure, a wideband diversity antenna with an 87.5% relative -6 dB impedance bandwidth, and a wideband MIMO antenna with a 95.0% relative -6 dB impedance bandwidth, are presented with excellent radiation and correlation properties. Also mutual coupling is need to be counted when multi-element antennas are designed. When designing an efficient radiator, it is important to consider an antenna feeding in terms of wideband impedance matching and wideband baluns, not to spoil the antenna performance. The efficient antenna structures and feeding mechanisms are obtained by using commercial 3D electromagnetic simulators to find the desired wideband antenna characteristics. Prototype antennas are measured in most of the presented structures to show their functionality in real. In general, the dissertation presents wideband antenna structures with radiating antenna modes excited on a planar conducting ground plane. The idea is to find structures and feeding mechanisms to excite the fundamental mode, or a certain radiating antenna mode, at a wide frequency bandwidth, by avoiding the excitation of higher order modes which might disturb the antenna performance. It is also shown that, by using multiple feeding elements, it is possible to excite higher order modes on a small antennaTiivistelmä Väitöskirjassa esitetään uusia laajakaistaisia ja monielementtiantenneja matkaviestimiin. Väitöskirja koostuu neljästä pääalueesta: pintavirtojen muototeoria, laajakaistaiset antennit, monielementtiantennit sekä laajakaistaiset monielementtiantennit. Teoriaosassa säteilykenttiä on aluksi tutkittu pallon pinnalla sekä skalaaripotentiaaleina että pintavirtavektoreina, jonka jälkeen niitä on verrattu mobiilin laitteen maatason ominaispintavirtojen synnyttämiin säteilykenttiin. Teoriaosassa osoitetaan, että pallon pinnalla sekä tasomaisella suorakaiteen muotoisella pinnalla on mahdollista herättää samat säteilykentät. Myöhemmin väitöskirjassa esitettävien uudenlaisten antennirakenteiden ominaisuuksia verrataan teoriaosassa esitettyihin pintavirtoihin ja säteilykenttiin. Teoriaosuuden jälkeen osoitetaan miten säteilevä sähkömagneettinen kenttä saadaan herätettyä laajalla taajuusalueella. Tähän on otettu kaksi eri lähestymistapaa, joista ensimmäisessä esitellään ja tutkitaan kvasikomplementaarista antennirakennetta (QCA). Kvasikomplementaarisessa antennirakenteessa sisääntuloimpedanssin imaginaariosa kompensoidaan yhdistämällä sähköinen johde ja magneettinen rako samaan antenniin. Samanaikaisesti perusmuoto herätetään laajalla taajuusalueella, jolla varmistetaan antennin hyvät säteilyominaisuudet koko toimintataajuusalueella. Toisessa lähestymistavassa käytetään kahta symmetrisesti asetettua antennielementtiä, joita syötetään symmetrisesti samalla amplitudilla ja vaiheella. Kun sähkömagneettinen kenttä herätetään symmetrisesti, korkeamman kertaluvun muotojen herättäminen voidaan välttää laajalla taajuusalueella. Symmetrisesti syötetyillä antennirakenteilla saavutettu -6 dB suhteellinen impedanssikaistanleveys on 37.5–80 %. Useita syöttöelementtejä käytettäessä voidaan mobiilin laitteen maatasossa herättää yhdellä pistetaajuudella monta toisistaan riippumatonta säteilykenttää. Koska herätetyt kentät ovat toisistaan riippumattomia, on niiden välinen korrelaatio myös pieni. Kyseisellä rakenteella on mahdollista toteuttaa säteilykuviodiversiteetti erittäin pienessä tilassa, kuten matkapuhelimessa. Toisaalta, kun yhdistetään kaksi QCA-elementtiä yhdeksi monielementtiratkaisuksi, voidaan toteuttaa laajakaistainen diversiteettiantenni, jonka suhteellinen -6 dB impedanssikaistanleveys on 87.5 %. Vastaavasti kahdella laajakaistaisella QCA-elementillä toteutetulla MIMO-ratkaisulla päästään 95 % suhteelliseen -6 dB impedanssikaistanleveyteen. Molemmilla ratkaisuilla on erittäin hyvät säteilyominaisuudet sekä alhainen korrelaatio ja pieni keskinäiskytkentä antennielementtien välillä. Suunniteltaessa toimivaa laajakaistaista antennirakennetta, on tärkeää ottaa huomioon antennisyötön impedanssisovitus, jotta antennin suorituskyky ei heikkenisi. Lisäksi balansoidussa rakenteissa tulee olla laajakaistainen baluni, jolla vältetään säteilykuvion vääristyminen. Väitöskirjan syöttöratkaisuissa on käytetty kaupallisia sähkömagneettisia simulaattoreita, joilla antennirakenne voidaan mallintaa kolmiulotteisesti, ja joilla laajakaistainen syöttö saadaan optimoitua haluttuun antenniin. Suurin osa esitellyistä antennirakenteista on simulointien lisäksi myös mitattu, jolloin niiden toimivuus käytännössä pystytään todentamaan rakentamalla prototyyppiantenni. Yleisesti väitöskirjassa esitellään tasomaisia antenniratkaisuja johtavassa maatasossa, joissa säteilevät pintavirrat herätetään mahdollisimman laajalla taajuusalueella. Ideana on löytää laajakaistaisia antenni- ja syöttörakenteita, joilla saadaan herätettyä perusmuoto tai jokin muu haluttu muoto. Ajatuksena on välttää korkeamman kertaluvun muotojen herättäminen, jotka voivat pilata antennin suorituskyvyn. Väitöskirjassa osoitetaan myös, että pienikokoisella antennilla on mahdollista herättää korkeamman kertaluvun muotoja pistetaajuudella käyttämällä useita heräte-elementtejä
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Hebelka, Vladimír. "Antény pro bezdrátové sítě pracující v blízkosti lidského těla." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2015. http://www.nusl.cz/ntk/nusl-234369.
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Disertační práce je zaměřena na vytvoření návrhu antény operující v blízkosti lidského těla. Kritické parametry zahrnují impedanční přizpůsobení, polarizační vlastnosti a vyzařovací charakteristiky. Základní výzkum je proveden na zjednodušených modelech lidského těla, kde jsou striktně definovány materiálové vlastnosti. Pro pokročilejší analýzu jsou využity detailnější modely. Simulace jsou konfrontovány s měřením na reálných vzorcích. V práci zahrnujeme interakci mezi anténou a lidským tělem.
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Jan, Naeem A. "Anomalous Nature Of Metamaterial Inclusion and Compact Metamaterial-Inspired Antennas Model For Wireless Communication Systems. A Study of Anomalous Comportment of Small Metamaterial Inclusions and their Effects when Placed in the Vicinity of Antennas, and Investigation of Different Aspects of Metamaterial-Inspired Small Antenna Models." Thesis, University of Bradford, 2017. http://hdl.handle.net/10454/16003.
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Metamaterials are humanly engineered artificial electromagnetic materials which produce electromagnetic properties that are unusual, yet can be observed readily in nature. These unconventional properties are not a result of the material composition but rather of the structure formed. The objective of this thesis is to investigate and design smaller and wideband metamaterial-inspired antennas for personal communication applications, especially for WiMAX, lower band and higher band WLAN applications. These antennas have been simulated using HFSS Structure Simulator and CST Microwave Studio software. The first design to be analysed is a low-profile metamaterial-inspired CPW-Fed monopole antenna for WLAN applications. The antenna is based on a simple strip loaded with a rectangular patch incorporating a zigzag E-shape metamaterial-inspired unit cell to enable miniaturization effect. Secondly, a physically compact, CSRR loaded monopole antenna with DGS has been proposed for WiMAX/WLAN operations. The introduction of CSRR induces frequency at lower WLAN 2.45 GHz band while the DGS has provided bandwidth enhancement in WiMAX and upper WLAN frequency bands, keeping the radiation pattern stable. The next class of antenna is a compact cloud-shaped monopole antenna consisting of a staircase-shaped DGS has been proposed for UWB operation ranges from 3.1 GHz to 10.6 GHz. The novel shaped antenna along with carefully designed DGS has resulted in a positive gain throughout the operational bandwidth. Finally, a quad-band, CPW-Fed metamaterial-inspired antenna with CRLH-TL and EBG is designed for multi-band: Satellite, LTE, WiMAX and WLAN.
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Elghannai, Ezdeen Ahmed. "NOVEL METHOD TO CONTROL ANTENNA CURRENTS BASED ON THEORY OF CHARACTERISTIC MODES." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1471871173.
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Pirkl, Ryan J. "Measurement-based investigations of radio wave propagation: an exposé on building corner diffraction." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/33961.
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Predicting performance metrics for the next-generation of multi-mode and multi-antenna wireless communication systems demands site-specific knowledge of the wireless channel's underlying radio wave propagation mechanisms. This thesis describes the first measurement system capable of characterizing individual propagation mechanisms in situ. The measurement system merges a high-resolution spatio-temporal wireless channel sounder with a new field reconstruction technique to provide complete knowledge of the wireless channel's impulse response throughout a 2-dimensional region. This wealth of data may be combined with space-time filtering techniques to isolate and characterize individual propagation mechanisms. The utility of the spatio-temporal measurement system is demonstrated through a measurement-based investigation of diffraction around building corners. These measurements are combined with space-time filtering techniques and a new linear wedge diffraction model to extract the first semi-mpirical diffraction coefficient. Specific contributions of this thesis are:
* The first ultra-wideband single-input multiple-output (SIMO) channel sounder based upon the sliding correlator architecture.
* A quasi 2-dimensional field reconstruction technique based upon a conjoint cylindrical wave expansion of coherent perimeter measurements.
* A wireless channel ``filming' technique that records the time-domain evolution of the wireless channel throughout a 2-dimensional region.
* High-resolution measurements of the space-time wireless channel near a right-angled brick building corner.
* The application of space-time filtering techniques to isolate the edge diffraction problem from the overall wireless channel.
* An approximate uniform geometrical theory of diffraction (UTD)-style linear model describing diffraction by an impedance wedge.
* The first-ever semi-empirical diffraction coefficient extracted from in situ measurement data.
This thesis paves the way for several new avenues of research. The comprehensive measurement data provided by channel "filming" will enable researchers to develop and implement powerful space-time filtering techniques that facilitate measurement-based investigations of radio wave propagation. The measurement procedure described in this thesis may be adapted to extract realistic reflection and rough-surface scattering coefficients. Finally, exhaustive measurements of individual propagation mechanisms will enable the first semi-empirical propagation model that integrates empirical descriptions of propagation mechanisms into a UTD-style mechanistic framework.
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Jaafar, Hussein. "Antennes miniatures, large bande et superdirectives à charges optimisées par l'analyse des modes caractéristiques." Thesis, Rennes 1, 2018. http://www.theses.fr/2018REN1S031/document.
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L'évolution rapide dans les systèmes de communication sans fil nécessite plus de miniaturisation de divers composants électroniques en plus de l'élément majeur de la technologie sans fil : l'antenne. Dans ce cas, une antenne occupant un espace limité devrait être miniaturisée pour fonctionner aux bandes de communication souhaitées. Cependant, à mesure que la taille électrique de l'antenne diminue, ses performances se dégradent considérablement et sa bande passante, son efficacité et sa directivité sont limitées. Les techniques classiques de réduction de la taille avec chargement de matériau et mise en forme géométrique de l'antenne souffrent d'une bande passante étroite et d'une faible efficacité de rayonnement. D'autre part, les tentatives d'augmenter la directivité des petites antennes en utilisant des réseaux superdirectifs sont également associées à une faible efficacité de rayonnement bande passante très étroite. Pour pallier ces inconvénients, nous proposons de booster les performances des antennes compactes en utilisant des charges réactives embarquées. En plaçant correctement les charges (actives ou passives) à l'intérieur de l'antenne, il est possible de contrôler les courants pour améliorer de manière significative les performances de l'antenne en termes de bande passante et de directivité. Cependant, pour un succès des critères de chargement, il est obligatoire d'analyser les modes naturellement supportés par l'antenne étudiée. On les appelle les modes caractéristiques, qui fournissent des aperçus physiques profonds sur le comportement de l'antenne et ses modes de rayonnement. En combinant cette théorie avec l'algorithme d'optimisation, il devient possible de manipuler de manière optimale les courants à l'intérieur de l'antenne en utilisant des charges réactives pour obtenir des conceptions large bande, superdirectives et efficacesThe rapid evolution in the wireless communication systems requires more miniaturization of various electronic components in addition to the major element of the wireless technology: the antenna. In this case, an antenna occupying a limited space should be miniaturized in order to operate at the desired communication bands. However, as the electrical size of the antenna decreases, its performance degrades dramatically and it becomes limited in bandwidth, efficiency, and directivity. Classical size reduction techniques with material loading and geometry shaping of the antenna suffer from narrow bandwidth and low radiation efficiency. On the other hand, attempts to increase the directivity of small antennas using superdirective arrays are also associated with low radiation efficiency and very narrow bandwidth. To overcome these drawbacks, we propose boosting the performance of compact antennas using embedded reactive loads. By properly placing loads (active or passive) inside the antenna, it is possible to control the currents to significantly enhance the antenna performance in terms of bandwidth and directivity. Yet, for a successful loading criteria, it is mandatory to analyze the modes that are naturally supported by the antenna under study. These are called the characteristic modes, which provide deep physical insights about the behaviour of the antenna and its radiating modes. By combining this theory with and optimization algorithm, it becomes possible to optimally manipulate the currents inside the antenna using reactive loads to achieve wideband, superdirective and efficient designs
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Lambert, Kevin M. "An environmental model for calculating the antenna temperature of earth based microwave antennas /." The Ohio State University, 1987. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487327695622938.
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Presse, Anthony. "Conception d'antennes souples et de conducteurs magnétiques artificiels en bande UHF." Thesis, Rennes 1, 2015. http://www.theses.fr/2015REN1S087/document.
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L'invention de l'antenne fût à la base de la création des communications sans fil à l'orée du XXe siècle. A l'origine des objets métalliques destinés à transmettre et recevoir des ondes électromagnétiques, les antennes n'ont cessé de se complexifier pour satisfaire l'impressionnant développement des communications sans fil. C'est dans ce contexte qu'est né le concept d'antenne « wearable » il y a moins de deux décennies ouvrant un nouveau champ de recherche sur les antennes souples. C'est dans ce cadre que ce travail de thèse se consacre à la conception d’antennes souples en bande UHF.Une première étude a permis de concevoir une antenne Vivaldi antipodale [150 - 900 MHz] souple pour la Section Technique de l'Armée de Terre. Six de ces antennes sont destinées à être placées sous un ballon gonflé à l'hélium pour réceptionner des signaux RF.Une seconde étude est effectuée en collaboration avec la société Syrlinks et le CNES. L'objectif du projet est de concevoir des antennes souples pour le suivi de personnes avec le système ARGOS (401 et 466 MHz). La solution retenue est une PIFA planaire de largeur inférieure à lambda/3. Elle a l'avantage d'être fine et légère. Le matériau souple employé est un caoutchouc silicone sélectionné parmi plusieurs matériaux souples grâce à des caractérisations diélectriques. Cependant, le problème de cette antenne est qu'elle possède un rayonnement quasi-omnidirectionnel. Etant donné qu'il n'était pas envisageable d'utiliser un plan réflecteur métallique pour des raisons de dimensions, il a été décidé de concevoir un conducteur magnétique artificiel (CMA) souple. Toutefois, la conception de CMA dans le bas de la bande UHF se heurte à des difficultés de miniaturisation. Pour contourner ce problème, il a été développé deux concepts de CMA à cellules unitaires de faibles dimensions devant la longueur d'onde. La première solution utilise des capacités interdigitées et la seconde une structure double couche. Pour ces deux concepts, un modèle circuit est proposé et validé par des mesures expérimentales. Les mesures de l'association CMA - antenne montrent une bande passante suffisante pour des applications ARGOS et un rayonnement majoritairement dirigée dans la direction opposé à celle du CMAThe invention of antennas was the base of wireless communications appearance at the dawn of the twentieth century. Originally metal objects for transmitting and receiving electromagnetic waves, antennas have steadily become more complex to meet the impressive development of wireless communications. It is in this context that the concept of wearable antennas was born less than two decades ago opening a new field of research namely flexible antennas. It is in this framework that this thesis is dedicated to the design of flexible antennas for UHF band.A first study enabled the design of a flexible antipodal Vivaldi antenna [150-900 MHz] for Technical Section of the Army. Six of these antennas are intended to be placed under a balloon inflated with helium for receiving RF signals.A second study was conducted in collaboration with the company Syrlinks and CNES. The objective of the project is to design flexible antennas for tracking people with ARGOS system (401 and 466 MHz). The selected solution is a planar PIFA which width is smaller than lambda/3. This antenna has the advantage of being thin and light. The flexible material used is a silicone rubber and it was selected among several others due to some dielectric characterizations. However, the drawback of this antenna is that it has a quasi-omnidirectional radiation pattern. Since it was not possible to use a reflector metal plane due to size constraints, it was decided to design a flexible artificial magnetic conductor (AMC). However, the design of AMCs in the lower UHF band is challenged with the miniaturization difficulties. Two concepts of small size (compared to the wavelength) AMCs unit cells were developed to work around this problem. The first solution uses interdigitated capacitors and the second a double layer structure. For these two concepts, a circuit model is proposed and validated by experimental measurements. The measurement of the AMC associated antenna demonstrates a bandwidth sufficient for ARGOS applications and a radiation pattern mostly directed in the direction opposite to that of the AMC
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Surittikul, Nuttawit. "Pattern reconfigurable printed antennas and time domain method of characteristic modes for antenna analysis and design." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1143225860.
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Obeidat, Khaled Ahmad. "Design Methodology for Wideband Electrically Small Antennas (ESA) Based on the Theory of Characteristic Modes (CM)." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1274730653.
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Raines, Bryan Dennis. "Systematic Design of Multiple Antenna Systems Using Characteristic Modes." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1306951104.
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Smierzchalski, Maciej. "Characterization methods for metamaterials : directive antennas using space eigen-mades." Thesis, Rennes 1, 2014. http://www.theses.fr/2014REN1S126/document.
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Ce travail de thèse est composé de deux partie distinctes. La première partie est consacrée à l'étude et la modélisation des métamatériaux et tout particulièrement à leur caractérisation. Il s'agit donc de proposer des paramètres constitutifs équivalents (permittivité, perméabilité et couplage magnéto-électrique) qui permettent de remplacer les métamatériaux, composés à l'origine de réseaux périodiques de cellules discrètes, par des milieux homogènes et continus. Deux régimes sont considérés : sub-longueur d'onde et longueur d'onde. Dans le premier régime, les dimensions de la cellule de base, en particulier la période du réseau, sont très faibles devant la longueur d'onde. Le métamatériau est alors modélisé par un milieu bi-anisotrope continu. Pour le deuxième régime, les dimensions et la période sont comparables à la longueur d'onde. Les paramètres constitutifs sont alors définis au sens "local" qui prend en compte le caractère discret et périodique de la structure. Enfin, la caractérisation consiste à extraire les paramètres constitutifs à partir des coefficients de réflexion et de transmission d'une lame de métamatériau. Pour cela, nous appliquons la méthode d'inversion sous sa forme classique pour le régime "sub-longueur d'onde" et son extension aux structures périodiques pour le régime "longueur d'onde". L'une des contributions majeure de ce travail est l'application des incidences obliques (à l'interface air-métamatériau) pour extraire les paramètres constitutifs longitudinaux. La seconde partie de ce travail de thèse concerne le développement d'antennes directives à partir de sources rayonnantes à modes orthogonaux. Il est bien connu que la directivité est directement limitée par les dimensions de l'antenne ou par le nombre de sources dans un réseau. L'objectif est de mettre en œuvre une méthode alternative qui, tout au moins sur le plan conceptuel et théorique, ne relie pas la directivité à la taille de l'antenne. Nous utilisons donc la combinaison de modes rayonnants orthogonaux pour maximiser la directivité d'antennes tout en minimisant les dimensions du réseau et en limitant le couplage. Chaque source du réseau se doit rayonner un mode propre et unique qui, combiné avec une autre source, permet d'augmenter la directivité. Pour cette étude, le développement théorique des modes sphériques puis cylindriques est tout d'abord présenté afin de mettre en évidence le lien entre la directivité et les modes. En pratique, la mise en œuvre de modes sphériques a révélé des difficultés de conception, si bien que des solutions d'antennes basées sur l'anneau rayonnant sont proposées pour réaliser des sources à modes orthogonaux "cylindriques". Les topologies de structures rayonnantes directives proposées associant des antennes anneaux sont validées en simulation et par la conception puis la mesure de prototypesThe work presented in this thesis concerns two parts: characterisation methods for metamaterials and directive antennas using space eigen-modes. The first one describes the homogenisation methods of metamaterials to retrieve the constitutive parameters from scattering parameters of the metamaterial's slab. We investigated the metamaterials which present the most common properties of media: bi-isotropic metamaterials (chiral), anisotropic metamaterials (BC-SRR), uni-axial bi-anisotropic metamaterials (double omega medium) and bi-axial bi-anisotropic metamaterials (EC-SRR). The transverse and longitudinal constitutive parameters characterising the anisotropic and bi-anisotropic require to examine the media at normal and oblique incidences. In the analysis we considered to distinguish continuous media restricted to long wave limit and resonating particles lattice which are out of long wave limit. The application of continuous media approach to the resonating particle lattice with size not satisfying the long wave limit can leads to violation of causality and passivity laws. The main different between proposed two approaches is interpretation of boundary conditions (Maxwellian/non-Maxwellian) for the metamaterial slab. The inclusions of lattice we ascribe as electric and magnetic dipole moments to develop an homogeneous resonating particles lattice and to retrieve the constitutive parameters. We validated the proposed approaches and compared the retrieved constitutive parameters according to physical laws. We found that the application of Bloch admittance and equivalence to electric and magnetic dipole moments provides the physical constitutive parameters. The second part of the thesis refers to directive antenna using space eigen-modes. The directivity of the antennas is limited to the size of the antenna or number of elements in an array. In common with keeping small sizes of the array the space between radiation elements has to be minimised. The proposed directive antenna considers the radiation elements determine by the orthogonal modes, i.e. each radiator of the array corresponds to unique space eigen-mode. This allows to ensure small distance between the array elements without introduction of high mutual coupling between them. The original approach refers to superposition of spherical modes however it is not practical. Instead of spherical modes we propose superposition of cylindrical modes which are easy to be realised. For the constructive summation of cylindrical modes and maximisation of directivity in end-fire plane we determine amplitudes of the cylindrical modes excited by electric and/or magnetic vector potentials. The cylindrical modes we obtain by the annular ring antennas and miniaturised annular rings. The superposition of cylindrical modes is achieved with a stacked antenna of annular rings and a coplanar cylindrical annular rings antenna. The both antennas we realised and measured
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Liu, Lingjia. "On delay-sensitive communication over wireless systems." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-2725.
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Diallo, Alpha Ousmane. "Modélisation hyperfréquence de problèmes multi-échelles appliquée au cas des antennes à métamatériaux diélectriques." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066356/document.
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Ce travail de thèse s’intéresse à l’amélioration de la compacité des antennes destinées en priorité aux systèmes embarqués tout en respectant les exigences de performance et de compétitivité. L’approche explorée consiste à utiliser des matériaux artificiels fonctionnant en transmission et conçus en structurant la matière diélectrique à une échelle plus petite que la longueur d’onde (sub-longueur d’onde). Cette structuration permet en pratique d’opérer une variation de l’indice de réfraction effectif afin de réaliser des éléments diffractifs aptes à remplir une fonction hyperfréquence. Cependant, la particularité de ce type d’élément structuré est de mêler plusieurs échelles physiques engendrant une complexité dans leur étude. La plus grande dimension d’un composant structuré peut atteindre plusieurs dizaines de longueur d’onde, par exemple 20λ, alors que la taille minimale des structures sub-longueur d’onde peut être inférieure à une fraction de la longueur d’onde, tel que λ/20. Cet aspect multi-échelle allonge les temps de simulation des dispositifs antennaires intégrant ces éléments structurés, empêchant ainsi toute possibilité d’optimisation multi-paramètres dans des temps raisonnables. Afin de pouvoir exploiter pleinement le potentiel de ces matériaux structurés, un modèle numérique de calcul a été développé sur la base des chemins optiques. Ce modèle restitue des résultats sur le maximum de gain des antennes lentilles diffractives structurées avec une précision de 0,5 dB. Le temps de calcul du modèle est de l’ordre de la minute comparée à plus de 6 heures pour une simulation complète avec le logiciel de calcul électromagnétique CST. La rapidité et la précision de ce modèle ont été mises à profit pour optimiser la conception d’une lentille diffractive structurée. Pour illustrer la pertinence de cette approche structurée, ses performances ont été comparées à celles des antennes lentilles de Fresnel et à profil hyperbolique. Cette comparaison s’est faite dans des conditions d’encombrement identiques avec un rapport longueur sur diamètre L/D de 0,5. Le gain de la lentille structurée se révèle être plus élevé de 1,6 dB par rapport à celui de la lentille de Fresnel et de 2,7 dB par rapport à celui de la lentille hyperboliqueThis work focuses on the improvement of the antennas compactness used primarily for embedded systems while respecting the performance and competitiveness requirements. The approach explored consists in using artificial materials operating in transmission and designed by structuring the dielectric material on a scale smaller than the wavelength (sub-wavelength). This structuring makes it possible in practice to achieve a variation in the effective refractive index in order to produce diffractive elements capable of performing a microwave function. However, the particularity of this type of structured element is to mix several physical scales generating complexity in their study. The largest dimension of a structured component can reach several tens of wavelength, for example 20λ, while the minimum size of the sub-wavelength structures may be less than a fraction of the wavelength, as than λ / 20. This multi-scale aspect increases the simulation times of antenna devices integrating these structured elements, thus preventing any possibility of multi-parameter optimization in reasonable times. In order to exploit fully the potential of these structured materials, a numerical model of computation has been developed on the basis of optical paths. This model gives results on the maximum gain of structured diffractive lens antennas with an accuracy of 0.5 dB. The computation time of the model is of the order of the minute compared to more than 6 hours for a complete simulation with the electromagnetic calculation software CST Microwave Studio. The speed and precision of this model have been used to optimize the design of a structured diffractive lens. To illustrate the relevance of this structured approach, its performances were compared with those of Fresnel lens antenna and hyperbolic lens antenna. This comparison was carried out under identical footprint conditions with a length to diameter ratio L / D of 0.5. The gain of the structured lens was found to be 1.6 dB higher than the Fresnel lens and 2.7 dB higher than the hyperbolic lens
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Paiva, Jordan Silva de. "Modelagem tensorial para estimaÃÃo de parÃmetros em arranjos de antenas polarimÃtricas." Universidade Federal do CearÃ, 2014. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=11393.
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Nesta dissertaÃÃo sÃo propostos mÃtodos baseados em processamento tensorial de sinais para a estimaÃÃo de parÃmetros em arranjos de antenas vetoriais elÃtricas (Tripolo), considerando diferentes estruturas de arranjos (ULA, L-shape e UPA). Inicialmente, à utilizado um arranjo em L-shape,resultando em um modelo tensorial de terceira ordem (3-D) que, junto ao algoritmo de estimaÃÃo T-ALS (do inglÃs, Trilinear Alternating Least Squares), possibilita a identificaÃÃo cega de pelo menos o dobro de fontes estimadas pelos modelos tradicionais. Em seguida, sob transmissÃo supervisionada, à proposto um mÃtodo alternativo, utilizando a decomposiÃÃo SVD, o qual à comparado ao mÃtodo tensorial com uso do algoritmo T-ALS. Uma segunda abordagem à proposta utilizando-se uma estrutura de arranjo planar de antenas (UPA), a qual faz uso de um modelo tensorial de quarta ordem (4-D) junto ao algoritmo de estimaÃÃo Q-ALS (do inglÃs, Quadrilinear Alternating Least Squares). Neste caso, um mÃtodo alternativo à proposto usando a fatoraÃÃo do produto de Khatri-Rao e uma anÃlise comparativa destes mÃtodos à realizada. Considerando-se o caso supervisionado, à feito ainda um estudo comparativo dos algoritmos Q-ALS, T-ALS e SVD, e um novo algoritmo, chamado Nested-SVD à proposto. Por fim, foi realizada a modelagem computacional do tripolo elÃtrico com uso de software de simulaÃÃo de alta frequÃncia (HFSS), possibilitando a extraÃÃo do parÃmetro de ganho espacial dos arranjos L-shape e UPA. Em seguida, à feita a avaliaÃÃo do desempenho dos mÃtodos tensoriais propostos usando este parÃmetro em uma situaÃÃo mais realista, e comparado ao desempenho usando modelos idealizados de arranjos de antenas com ganho unitÃrio e omnidirecional.
O desempenho dos mÃtodos propostos à avaliado atravÃs de simulaÃÃes de Monte Carlo em diferentes cenÃrios e configuraÃÃes de arranjoIn this dissertation, we propose methods based on tensor signal processing for the parameter estimation in electric vector (Tripole) antenna arrays, considering different structures of arrays (ULA, L-shape and UPA). Initially, using a L-shape array, we develop a third order (3-D) tensor model for the received data. Based on this model, a trilinear alternating least squares (T-ALS) algorithm is used for the blind estimation of the sourceâs parameters. Then, under supervised transmission an alternative method is proposed by resorting to the SVD decomposition, which is compared to the T-ALS algorithm. A second approach is proposed, which is based on a uniform planar array antenna (UPA). In this case a fourth-order (4-D) tensor model is obtained, and the Q-ALS (Quadrilinear Alternating Least Squares) algorithm is used for parameter estimation. An alternative method is also proposed, which exploits the factorization of the Khatri-Rao product. Considering the supervised case, a new algorithm called Nested-SVD is proposed and a comparative study with Q-ALS, T-ALS and SVD algorithms is carried out. The performance of the proposed methods is evaluated through Monte Carlo simulations in different scenarios and array settings. Finally, computational modeling of electric tripole using the high frequency simulation software (HFSS) was performed, enabling the extraction of the L-shape and UPA spatial array gain. Then, the performance of the proposed tensor methods is evaluated in a more realistic scenario, and compared to idealized omnidirectional and unitary gain antenna array models
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Elmegri, Fauzi O. M. "Model and design of small compact dielectric resonator and printed antennas for wireless communications applications : model and simulation of dialectric resonator (DR) and printed antennas for wireless applications : investigations of dual band and wideband responses including antenna radiation performance and antenna design optimization using parametric studies." Thesis, University of Bradford, 2015. http://hdl.handle.net/10454/14742.
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Dielectric resonator antenna (DRA) technologies are applicable to a wide variety of mobile wireless communication systems. The principal energy loss mechanism for this type of antenna is the dielectric loss, and then using modern ceramic materials, this may be very low. These antennas are typically of small size, with a high radiation efficiency, often above 95%; they deliver wide bandwidths, and possess a high power handling capability. The principal objectives of this thesis are to investigate and design DRA for low profile personal and nomadic communications applications for a wide variety of spectrum requirements: including DCS, PCS, UMTS, WLAN, UWB applications. X-band and part of Ku band applications are also considered. General and specific techniques for bandwidth expansion, diversity performance and balanced operation have been investigated through detailed simulation models, and physical prototyping. The first major design to be realized is a new broadband DRA operating from 1.15GHz to 6GHz, which has the potential to cover most of the existing mobile service bands. This antenna design employs a printed crescent shaped monopole, and a defected cylindrical DRA. The broad impedance bandwidth of this antenna is achieved by loading the crescent shaped radiator of the monopole with a ceramic material with a permittivity of 81. The antenna volume is 57.0 37.5 5.8 mm3, which in conjunction with the general performance parameters makes this antenna a potential candidate for mobile handset applications. The next class of antenna to be discussed is a novel offset slot-fed broadband DRA assembly. The optimised structure consists of two asymmetrically located cylindrical DRA, with a rectangular slot feed mechanism. Initially, designed for the frequency range from 9GHz to 12GHz, it was found that further spectral improvements were possible, leading to coverage from 8.5GHz to 17GHz. Finally, a new low cost dual-segmented S-slot coupled dielectric resonator antenna design is proposed for wideband applications in the X-band region, covering 7.66GHz to 11.2GHz bandwidth. The effective antenna volume is 30.0 x 25.0 x 0.8 mm3. The DR segments may be located on the same side, or on opposite sides, of the substrate. The end of these configurations results in an improved diversity performance.
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Elmegri, Fauzi. "Model and design of small compact dielectric resonator and printed antennas for wireless communications applications. Model and simulation of dialectric resonator (DR) and printed antennas for wireless applications; investigations of dual band and wideband responses including antenna radiation performance and antenna design optimization using parametric studies." Thesis, University of Bradford, 2015. http://hdl.handle.net/10454/14742.
Full textAbstract:
Dielectric resonator antenna (DRA) technologies are applicable to a wide variety of
mobile wireless communication systems. The principal energy loss mechanism for this
type of antenna is the dielectric loss, and then using modern ceramic materials, this
may be very low. These antennas are typically of small size, with a high radiation
efficiency, often above 95%; they deliver wide bandwidths, and possess a high power
handling capability.
The principal objectives of this thesis are to investigate and design DRA for low profile
personal and nomadic communications applications for a wide variety of spectrum
requirements: including DCS, PCS, UMTS, WLAN, UWB applications. X-band and part
of Ku band applications are also considered. General and specific techniques for
bandwidth expansion, diversity performance and balanced operation have been
investigated through detailed simulation models, and physical prototyping.
The first major design to be realized is a new broadband DRA operating from 1.15GHz
to 6GHz, which has the potential to cover most of the existing mobile service bands.
This antenna design employs a printed crescent shaped monopole, and a defected
cylindrical DRA. The broad impedance bandwidth of this antenna is achieved by
loading the crescent shaped radiator of the monopole with a ceramic material with a
permittivity of 81. The antenna volume is 57.0 37.5 5.8 mm3, which in conjunction
with the general performance parameters makes this antenna a potential candidate for
mobile handset applications.
The next class of antenna to be discussed is a novel offset slot-fed broadband DRA
assembly. The optimised structure consists of two asymmetrically located cylindrical
DRA, with a rectangular slot feed mechanism. Initially, designed for the frequency
range from 9GHz to 12GHz, it was found that further spectral improvements were
possible, leading to coverage from 8.5GHz to 17GHz.
Finally, a new low cost dual-segmented S-slot coupled dielectric resonator antenna
design is proposed for wideband applications in the X-band region, covering 7.66GHz
to 11.2GHz bandwidth. The effective antenna volume is 30.0 x 25.0 x 0.8 mm3. The DR
segments may be located on the same side, or on opposite sides, of the substrate. The
end of these configurations results in an improved diversity performance.General Secretariat of Education and Scientific Research Libya
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Nuckols, John Eric. "Implementation of Geometrically Based Single-Bounce Models for Simulation of Angle-of-Arrival of Multipath Delay Components in the Wireless Channel Simulation Tools, SMRCIM and SIRCIM." Thesis, Virginia Tech, 1999. http://hdl.handle.net/10919/35989.
Full textAbstract:
As the demand for wireless communication systems has exploded over the past few years, many researchers have taken on the challenge to model wireless channels more accurately. These models are very useful for enhancing the design of all aspects of wireless communications. Smart antennas and systems used in position location are among the most popular new studies that require signal information such as the amplitude, phase, and angle-of-arrival (AOA) of multipath delay spreads. For proper and efficient implementation of future systems, emerging wireless systems must be able to exploit processing of spatial information. The goal of the work presented in this thesis is to further improve two channel modeling tools, SMRCIM and
SIRCIM, by implementing new geometrical models that provide users with angle-of-arrival information as well as amplitude and phase data for wideband wireless communication channels. The new angle-of-arrival models are explained and pseudo code is provided to demonstrate the software implementation of the models. Likewise, the channel models are explained and the usage and results of the simulation tools are described. The SMRCIM and SIRCIM tools are currently being used by researchers throughout the world.
[Vita removed March 5, 2012. GMc]
Master of Science
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Ulrich, Gary A. "Computer model for a towed submarine communication antenna." Thesis, Springfield, Va. : Available from National Technical Information Service, 1999. http://handle.dtic.mil/100.2/ADA372223.
Full textAbstract:
Thesis (Degree of Naval Engineer and M.S. in Mechanical Engineering) Massachusetts Institute of Technology, June 1999."June 1999". Includes bibliographical references (leaves 97-98). Also available online.
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Ulrich, Gary A. (Gary Alan) 1962. "Computer model for a towed submarine communication antenna." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/9551.
Full textAbstract:
Thesis (Nav.E.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1999.Includes bibliographical references (leaves 97-98).
A finite difference computer model is developed to simulate the exposure statistics of a radio frequency buoyant antenna as it is towed in a random seaway. The model allows the user to prescribe antenna properties (length, diameter, density, etc.), sea conditions ( significant wave height, development of sea), and tow speed. The model then simulates the antenna-sea interaction for the desired duration to collect statistics relating to antenna performance. The model provides design engineers with a tool to predict antenna performance trends, and conduct design tradeoff studies. The antenna envisioned is a submarine floating antenna which would enable communications at speed and depth, greatly enhancing the stealth and survivability of the US Navy's submarine force.
by Gary A. Ulrich.
S.M.
Nav.E.
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Patwari, Neal. "Measured and Modeled Time and Angle Dispersion Characteristics of the 1.8 GHz Peer-to-Peer Radio Channel." Thesis, Virginia Tech, 1999. http://hdl.handle.net/10919/32201.
Full textAbstract:
In an extensive outdoor propagation study, low antenna heights of
1.7 m are used at both the transmitter and the receiver to measure
over 3500 wideband power-delay profiles (PDPs) of the channel for
a peer-to-peer communications system. Rural and urban areas are
studied in 22 different transmitter-receiver links. The results
are used to characterize the narrowband path loss, mean delay,
root-mean-square (RMS) delay spread, and timing jitter of the
peer-to-peer wideband channel. Small-scale fading characteristics are
measured in detail by measuring and analyzing 160 PDPs within each
local area. This thesis shows the measurement setup for the
calculation of fading rate variance and angular spread and reports
the first known attempt to calculate angular spread from track
power measurements. New analysis presented in this thesis shows
the effect of measurement error in the calculation of angular
spread. The expected characteristics of angular spread are
derived using two different angle-of-arrival (AOA) models from the
literature. Measurement results show initial validation of
Durgin's angular spread theory. A new measurement-based algorithm
for simulating wideband fading processes is developed and
implemented. This simulation technique shows promise in the
simulation of high-bit rate peer-to-peer radio communication
systems.Master of Science
36
Diallo, Kadidiatou. "Antennes miniatures basses fréquences, reconfigurables pour le LTE." Thesis, Université Côte d'Azur, 2021. http://www.theses.fr/2021COAZ4010.
Full textAbstract:
Cette thèse porte sur l’étude, la conception et l’optimisation d’antennes miniatures, multi-bandes et agiles en fréquence, destinées à des applications IoT et mobiles dans les bandes LTE et 5G sub-6 GHz. Ces antennes sont réalisées sur des plans de masse de dimensions 120x60 mm². D’abord la conception d’une antenne PIFA bi-bande, couvrant les bandes ISM 868 MHz et 915 MHz est effectuée. Ensuite, nous avons proposé la conception et l’optimisation d’un système multi-antennaires multistandards à deux accès, fonctionnant sur les fréquences basses de la bande LTE (700 à 900 MHz) et couvrant en même temps la bande LTE 2600 et une partie de la bande 5G [3,4 - 3,8 GHz]. Ce système antennaire est constitué de deux antennes PIFAs associées à des éléments parasites également de type PIFA, permettant l’élargissement de leurs bandes passantes dans certaines bandes de fréquences. L’une des antennes fonctionne sur trois bandes de fréquences, elle est agile en fréquence sur sa bande basse. L’autre antenne opère quant à elle sur deux bandes fréquences (la bande LTE 2600 et la bande 5G 3600). L’agilité en fréquence de l’antenne reconfigurable est obtenue au moyen d’une diode varactor polarisée directement sur le port d’alimentation de l’antenne à l’aide d’un circuit LC parallèle, connecté sur sa ligne d’alimentation. Enfin, grâce à l’étude des modes caractéristiques du plan de masse, les positions des différentes antennes du système MIMO sont choisies de manière à ce qu’elles soient naturellement isolées sans l’emploi des méthodes de découplage classiques. Le système final couvre la bande LTE [700 - 900 MHz], reconfigurable en fréquence, la bande LTE 2600 et une partie de la bande 5G [3,4 - 3,8 GHz]. Les mesures ont montré une bonne isolation des antennes (|S21| -20 dB) dans les deux bandes où le système fonctionne en mode MIMO. Les efficacités mesurées dans la bande reconfigurable ne sont pas très élevées, cependant, elles restent correctes pour l’application viséeThis thesis focuses on the study, design and optimization of miniature multiband and frequency reconfigurable antennas for IoT and mobile applications in LTE and 5G frequency bands. Ground planes of dimensions 120*60 mm² were used. First the design of a dual-band PIFA antenna operating in the ISM 868 MHz and 915 MHz bands is carried out. Then, we proposed the design and optimization of a two-port multi-antenna system, operating on the low frequency LTE band (from 700 MHz to 900 MHz) and covering at the same time the LTE 2600 band and part of the 5G middle band. This antenna system consists of two PIFAs antennas associated with parasitic elements that used to expand their bandwidths in certain frequency bands. One of the antennas operates on three frequency bands and it is frequency tunable on the low band. The other antenna operates only on two frequency bands, the LTE 2600 band (from 2500 MHz to 2700 MHZ) and 5G middle band (from 3.4 GHz to 3.8 GHz). The frequency agility of the reconfigurable antenna is achieved by using a varactor diode which is directly biased on antenna feeding port. Finally, thanks to the study of the characteristic modes of the ground plane, the positions of the MIMO system antennas are chosen so that they are naturally isolated without the use of conventional decoupling methods. The final system covers the LTE [700 - 900 MHz] band, reconfigurable in frequency, the LTE 2600 band and part of the 5G middle band. The measurements showed good port isolation (|S21| -20 dB) in the two bands where the system operates in MIMO mode. The efficiencies measured in the reconfigurable band are not very high, however, they remain correct for the intended application
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Cardia, Daniel Vitor Faria. "Determinação de modelos simplificados de fontes equivalentes de campos elétricos e magnéticos aplicáveis à análise de compatibilidade eletromagnética de sistemas embarcados." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/3/3143/tde-12032018-083256/.
Full textAbstract:
Neste trabalho apresentar-se-á um método para a determinação de modelos simplificados de fontes equivalentes de campos elétricos e magnéticos aplicáveis à análise de compatibilidade eletromagnética de sistemas embarcados. Esses modelos são obtidos a partir de medições laboratoriais, com técnicas de cálculos analíticos, numéricos e híbridos. Destacam-se, o fato da utilização do método de medição através de antenas de grandes loops (ou, laços, em português), na determinação de fontes equivalentes de emissão radiada e a aplicação destas na avaliação dos campos eletromagnéticos radiados. A contribuição deste trabalho é a obtenção dessas fontes equivalentes de emissão radiada, que possibilitam a avaliação da contribuição dos campos elétricos e magnéticos em ambientes eletromagnéticos. E também contribui com a aplicação de uma metodologia para a obtenção dos campos elétricos a partir dos campos magnéticos previamente determinados. Em particular, este trabalho pode ser considerado como decorrente da evolução da Dissertação de Mestrado [1].It will be shown in this work a method for simplified models determination of equivalent sources for electric and magnetic fields, applicable to embedded systems electromagnetic compatibility analysis. These models are obtained by laboratory tests with analytical calculation techniques associated to numerical and hybrid calculations. This work highlights the application of measurement method by Large Loop Antennas (LLAs) for the creation of radiated emission equivalent sources and the application of a corresponding method for obtaining radiated electromagnetic fields. The contribution of this work is the acquisition of these equivalent sources of radiated emission, which allows the evaluation of the magnetic and electric field contribution in electromagnetic environments. And it also contributes with the application of a methodology to obtain the electric fields from previously determined magnetic fields. In special, this work may be considered as an evolution of the Master\'s Thesis [1]
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Potgieter, Brendon Ryan. "Experimental modal analysis and model validation of antenna structures." Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/5423.
Full textAbstract:
Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2010.ENGLISH ABSTRACT: Numerical design optimisation is a powerful tool that can be used by engi- neers during any stage of the design process. Structural design optimisation is a specialised usage of numerical design optimisation that has been adapted to cater speci cally for structural design problems. A speci c application of structural design optimisation that will be discussed in the following report is experimental data matching. Data obtained from tests on a physical structure will be matched with data from a numerical model of that same structure. The data of interest will be the dynamic characteristics of an antenna structure, focusing on the mode shapes and modal frequencies. The structure used was a scaled, simpli ed model of the Karoo Array Telescope-7 (KAT-7) antenna structure. Experimental data matching is traditionally a di cult and time-consuming task. This report illustrates how optimisation can assist an engineer in the process of correlating a nite element model with vibration test data.
AFRIKAANSE OPSOMMING: Numeriese ontwerp-optimisering is 'n kragtige ingenieurshulpmiddel wat ty- dens enige stadium in die ontwerpsproses ingespan kan word. Strukturele ontwerp-optimisering is 'n gespesialiseerde gebruik van numeriese ontwerp- optimisering wat aangepas is om spesi ek van diens te wees by die oplos van strukturele ontwerpsprobleme. 'n Spesi eke toepassing van strukturele ontwerp-optimisering wat in hierdie verslag bespreek sal word, is eksperi- mentele datakorrelasie. Data afkomstig van toetse op 'n siese struktuur sal gekorreleer word met data afkomstig van 'n numeriese model van die selfde struktuur. Die data van belang is die dinamiese eienskappe van 'n anten- nastruktuur, spesi ek die modusvorme en modale frekwensies. Die betrokke struktuur wat gebruik is, is 'n vereenvoudigde skaalmodel van die Karoo Array Telescope-7 (KAT-7) antennastruktuur. Eksperimentele datakorrelasie is, tradisioneel gesproke, 'n moeilike en tydro- wende taak. Hierdie verslag sal illustreer op watter wyse optimisering 'n inge- nieur van hulp kan wees in die proses om 'n eindige elementmodel met vibrasietoetsdata te korreleer.
39
Laird, Daniel T. "Logistics Regression Model on Antenna Control Unit Autotracking Mode." International Foundation for Telemetering, 2015. http://hdl.handle.net/10150/596414.
Full textAbstract:
ITC/USA 2015 Conference Proceedings / The Fifty-First Annual International Telemetering Conference and Technical Exhibition / October 26-29, 2015 / Bally's Hotel & Convention Center, Las Vegas, NVOver the past several years DoD imposed constraints on test deliverables, requiring objective measures of test results, i.e., statistically defensible test and evaluation (SDT&E) methods and results. These constraints force testers to employ statistical hypotheses, analyses and modeling to assess test results objectively, i.e., based on statistical metrics, analytical methods, probability of confidence complemented by, rather than solely on expertise, which is too subjective. In this and companion papers we discuss methods of objectifying testing. We employ an earth coordinate model and statistical modeling of telemetry (TM) tracking antenna employing time-space position information (TSPI) and derived statistical measures for tracking-error and auto-tracking mode. Test data were statistically analyzed via analysis of covariance (ANCOVA) which revealed that the antenna control unit (ACU) under test (AUT) does not track statistically identically, nor as practically or efficiently in C-band while receiving data carriers in both S- and C-bands. The conclusions of this paper add support to that hypothesis. In this third of three papers we use data from a range test, but make no reference to the systems under test as the purpose of this paper is to present an example of tools useful for employing a SDT&E methodology.
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Juyal, Prateek. "Directive microstrip disc radiators based on TM1m modes." IEEE TAP, 2016. http://hdl.handle.net/1993/32074.
Full textAbstract:
Fundamental TM11 mode of circular microstrip antennas has a limitation of low broadside gain. This thesis explores and investigates the possibility of designing high gain circular microstrip antennas by using higher zeros of the first order mode, or the TM1m modes. Deficiencies in the existing methods of gain enhancement, motivates the need to look for new methods. This is done by first investigating the radiation characteristics of TM1m modes, and then providing techniques for sidelobe suppression in their radiation patterns. Several approaches are proposed and corresponding to each developed technique, an example of high gain antenna is designed, fabricated and experimentally evaluated.
First, through the radiation characteristics of a magnetic loop over an infinite ground plane, we explain the occurrence of high sidelobes in the E-plane radiation patterns of the TM1m modes. By noting the peak directivity and sidelobe variation with loop size, we propose, investigate and demonstrate the use of high permittivity substrates to reduce the sidelobes in the TM12 mode. Second, to remove the dependence of the radiation characteristics on high permittivity substrates, another technique to suppress the high sidelobes of TM12 mode, is presented. It is found that introducing a narrow nonresonant rectangular slot at the patch center, sidelobes of the TM12 mode can be effectively suppressed. Sidelobe level (SLL) suppression is demonstrated by both simulation and measurement, using various configurations.
Third, it is proposed that linearly superimposing the radiation fields of either odd or even zeros of the first order mode, can achieve both high gain and low sidelobes. To show this, stacked antenna configurations of TM11 and TM13 modes are thoroughly investigated and SLL suppression is demonstrated. Finally, to leverage further advantage of the linear superposition of modes, a single layer annular slot loaded antenna configuration is proposed.
The proposed new configurations are based on higher order TM1m modes, which, for excitation, requires electrically large conducting discs. This property offers one more advantage at high frequencies, where antenna size becomes too small for the fundamental mode to fabricate and feed. The proposed electrically large antennas eliminate these problems, and become more practical to fabricate.February 2017
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Strojny, Brandan Thomas. "EXCITATION AND ANALYSIS OF CHARACTERISTIC MODES ON COMPLEX ANTENNA STRUCTURES." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1301006813.
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Heyssler, Matthias. "Probing the standard model and beyond at high-energy colliders." Thesis, Durham University, 1998. http://etheses.dur.ac.uk/4873/.
Full textAbstract:
The thesis covers the following topics: Assuming a partonic structure of the Pomeron we give predictions for diffractive heavy flavour production at the Tevatron and the LHC and diffractive Higgs production at the LHC in leading-order approximation. For the latter the dominant background processes are also considered. We obtain results on single as well as double diffractive cross sections assuming a Donnachie-Landshoff-type Pomeron flux factor. Measurements of the single inclusive jet cross section at the Tevatron by the CDF Collaboration maybe suggest a modified picture of QCD in the large E(_T) range. A parameter fit of a neutral heavy vector boson Z(^1) to the CDF data, in leading order perturbation theory, is performed, and the question of how the corresponding single inclusive jet cross-sections and the dijet angular distributions at the LHC are affected by this additional Z' is discussed. We test a model, motivated by the former R(_b) and R(_c) "crisis", which contains extra vector fermions. We suggest an alternative indirect test of the possible existence of new heavy quark flavours at the LEP2 collider, which turns out to give the clearest signal. We calculate qq cross sections within this framework, including one loop corrections. Hadronic antenna patterns can provide a valuable diagnostic tool for probing the origin of the reported excess of high x, Q(^2) events at HERA. We present quantitative predictions for the distributions of soft particles and jets in standard deep inelastic scattering eq → eq events and in events corresponding to the production of a narrow colour-triplet scalar resonance. We also study the patterns corresponding to Higgs production and decay in high- energy hadron-hadron collisions. In particular, the signal gg → H → bb and background gg → bb processes are shown to have very different radiation patterns, and this may provide a useful additional method for distinguishing Higgs signal events from the QCD background. The process eq → eq + γ exhibits radiation zeros, i.e. configurations of the final-state particles for which the scattering amplitude vanishes. We study these zeros for both e(^+)u and e(^+)d scattering. The latter exhibits a new type of zero which to our knowledge has not previously been identified. The observability of radiation zeros at HERA is discussed. In the framework of this new type of zero we also study the process e(^+)e(^-) → qqγ. We calculate the positions of these zeros for u-quark and d-quark production and assess the feasibifity of identifying the zeros in experiments at high energies. The radiation zeros are shown to occur also for massive quarks, and we discuss how the bbγ final state may offer a particularly clean environment in which to observe them.
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Theodossopoulos, Konstantinos. "Rectilinear slot model of an inclined slot radiator in rectangular waveguide." Thesis, Heriot-Watt University, 2000. http://hdl.handle.net/10399/577.
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Ho, Chung-Man Peter. "Antenna effects on indoor wireless channels and a deterministic wide-band propagation model for in-building personal communication systems." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-01102009-063157/.
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Murray, Kevin Paul. "The design of antenna systems on complex structures using characteristic modes." Thesis, University of Liverpool, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385200.
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Костановський, Валерій Вікторович, and Valery V. Kostanovskyi. "Методологія підвищення ефективності технічного обслуговування активних фазованих антенних решіток радіолокаційних станцій." Thesis, Національний авіаційний університет, 2021. https://er.nau.edu.ua/handle/NAU/48988.
Full textAbstract:
Робота присвячена розвитку методології підвищення ефективності
технічного обслуговування активних фазованих антенних решіток (АФАР)
радіолокаційних станцій. У даній роботі розроблені та удосконалені
математичні моделі надійності і підвищення ефективності експлуатації
активних фазованих антенних решіток за критеріями технічного
використання і економічної ефективності.
В роботі удосконалені математичні моделей надійності електровиробів,
що описують раптові і поступові відмови. Розроблені та досліджені моделі
надійності необслугованих АФАР зі k – рівневою структурною схемою
надійності при раптових і поступових відмовах модулів антенних решіток.
Облік поступових відмов модулів антенних решіток дозволяє підвищити
надійність АФАР від 30 % до 80 %. Розроблені математичні моделі
надійності обслуговуваних АФАР. Удосконалені методи визначення
потрібної кількісті запасних модулів антенних решіток для забезпечення
технічного обслуговування АФАР.
Розроблені та досліджені моделі оптимального технічного
обслуговування РЛС з АФАР, застосування яких дозволяє знизити від 15 %
до 35 % наведених експлуатаційних витрат на етапі гарантійного
обслуговування. Визначені стратегії технічного обслуговування і
експлуатації АФАР РЛС з наробітку і фактичному стану, розроблені моделі
і методи для реалізації цих стратегій на етапі післягарантійного
обслуговування.The work is devoted to the development of the methodology for improving the efficiency of maintenance of active phased array antennas (APAA) of radar stations. In this paper, mathematical models of reliability and efficiency of operation of active phased array antennas according to the criteria of technical use and economic efficiency are developed and improved. Mathematical models of reliability of electrical products describing sudden and gradual failures are improved in the work. Reliability models of maintenance – free APAA with k – level structural scheme of reliability at sudden and gradual failures of antenna array modules are developed and investigated. Accounting for gradual failures of antenna array modules can increase the reliability of APAA from 30 % to 80 %. Mathematical models of reliability of serviced APAA are developed. Improved methods for determining the required number of spare antenna array modules to provide APAA maintenance. Developed and researched models of optimal maintenance of radars with APAA, the use of which allows to reduce from 15 % to 35 % of the operating costs at the stage of warranty service. Strategies for maintenance and operation of APAA radar based on operating time and actual condition are determined, models and methods for implementation of these strategies at the stage of post-warranty service are developed.
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Sung-hoon, Jang, Han Sung-hee, and Kim Heung-bum. "Auto-tracking antenna pattern effects on multipath channel model at test range." International Foundation for Telemetering, 2001. http://hdl.handle.net/10150/607672.
Full textAbstract:
International Telemetering Conference Proceedings / October 22-25, 2001 / Riviera Hotel and Convention Center, Las Vegas, NevadaTelemetry propagation channel is modeled to predict PCM/FM telemetry receiving signal level at APG(Anheung Proving Ground), ADD(Agency for Defense Development). Channel model is composed of direct wave and reflected wave in sea surface, so-called 2-ray model. Our 2-ray model includes transmitting antenna radiation pattern, auto-tracking antenna radiation pattern, sea surface reflection coefficient and phase depending on incident angle. Vertical and horizontal polarized receiving signal strength is obtained from pre-calculated flight trajectory of transmitter. Calculated results are compared with measured data in real flight test. 2-ray channel model can predict almost identical receiving signal level and calculate starting point of multi-path fading effect. Using these results, receiving system can be moved to more proper position before flight test.
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Kim, Kangwook. "Numerical and experimental investigation of impulse-radiating antennas for use in sensing applications." Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/14944.
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Afacan, Gonenc. "The Electrical Characteristics Of Antennas In Their Operational Environment." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/2/12609119/index.pdf.
Full textAbstract:
This thesis investigates the variations of electrical properties of linear antennas mounted on certain platforms, depending on the physical properties of that platform. In this respect, related basic antenna simulations, electromagnetic simulations from primitive to complex models of airframes, and scale model measurements were used.
Firstly, electrical properties of monopoles at known environment were examined and basic analyses were performed via an electromagnetic simulation tool, named CST Microwave Studio®. In addition, important aspects of simulation tool were investigated. Then, an F-4 aircraft model was used to observe the electrical characteristics of antennas mounted on it. Using 3D model of F-4 aircraft, realistic antenna placement points were assigned and monopoles were attached to those points. Alternatively, a simplified F-4 model was also used and for two different models, identical simulations were done, followed by accuracy and performance analysis between the results obtained from simplified and exact models. As the outcome of these simulations, certain parameters like impedance, antenna-to-antenna coupling and radiation pattern values were examined. Additionally, change in antennas&rsquo
electrical characteristics due to their position over the airframe was investigated. In addition, a 1:10 down-scaled and copper-plated F-4 aircraft model was obtained and equipped with identical antennas. By using the measurements done on this scale model, antenna-to-antenna coupling results of MWS®
were verified by measurements. Finally, advantages and disadvantages of using electromagnetic simulation tools and scale model measurements for such antenna studies were discussed.
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Padmosutoyo, Slamet Suharsa. "NEC, NECGS, and MININEC numerical models of LF top-hat monopole antennas." Thesis, Monterey, California. Naval Postgraduate School, 1989. http://hdl.handle.net/10945/26100.
Full textAbstract:
The US Navy needs to increase the power handling capability of its current VLF and LF top-hat monopole antennas. This is most efficiently studied via numerical analysis of candidate antennas. Previous computer models based on the Numerical Electromagnetics Code (NEC-3) were shown to be unacceptable. The reasons for the inaccuracies were discovered to be NEC's inability to accurately model the effects of step changes of radius on adjacent portions of the structure. This thesis investigates two additional numerical models. The first uses the MININEC SYSTEM which has been shown to be accurate for stepped-radius antennas, and the second approximates a top-hat monopole antennas by a wire-cage structure. The latter employs NECGS, a special version of NEC-3 which efficiently uses radial symmetry. The performance parameters of interest which were calculated are static capacitance, resonant frequency, effective height, and radiation resistance. The results of these new models are compared to scale- model measurements and to the numerical results of the earlier NEC-3 study. The MININEC SYSTEM product acceptable values but is limited in the number of unknowns used to describe the model. NECGS results indicate that an acceptable wire-cage equivalency to a top-hat monopole may not exist