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1
Lee, C. K. "Modelling and design of frequency selective surfaces for reflector antennas." Thesis, University of Kent, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376318.
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Forslund, Ola. "Scattering and propagation of electromagnetic waves in planar and curved periodic structures - applications to plane wave filters, plane wave absorbers and impedance surfaces." Doctoral thesis, KTH, Alfvén Laboratory, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3825.
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The subject of this thesis is scattering of electromagneticwaves from planar and curved periodic structures. The problemspresented are solved in the frequency domain.
Scattering from planar structures with two-dimensionalperiodic dependence of constitutive parameters is treated. Theconstitutive parameters are assumed to vary continuously orstepwise in a cross section of a periodically repeating cell.The variation along a longitudinal coordinate z is arbitrary. Ageneral skew lattice is assumed. In the numerical examples, lowloss and high loss dielectric materials are considered. Theproblem is solved by expanding the .elds and constitutiveparameters in quasi-periodic and periodic functionsrespectively, which are inserted into Maxwells equations.Through various inner products de.ned with respect to the cell,and elimination of the longitudinal vector components, a linearsystem of ordinary di.erential equations for the transversecomponents of the .elds is obtained. After introducing apropagator, which maps the .elds from one transverse plane toanother, the system is solved by backward integration.Conventional thin metallic FSS screens of patch or aperturetype are included by obtaining generalised transmission andre.ection matrices for these surfaces. The transmission andre.ection matrices are obtained by solving spectral domainintegral equations. Comparisons of the obtained results aremade with experimental results (in one particular case), andwith results obtained using a computer code based on afundamentally di.erent time domain approach.
Scattering from thin singly curved structures consisting ofdielectric materials periodic in one dimension is alsoconsidered. Both the thickness and the period are assumed to besmall. The .elds are expanded in an asymptotic power series inthe thickness of the structure, and a scaled wave equation issolved. A propagator mapping the tangential .elds from one sideto the other of the structure is derived. An impedance boundarycondition for the structure coated on a perfect electricconductor is obtained.
Keywords:electromagnetic scattering, periodicstructure, frequency selective structure, frequency selectivesurface, grating, coupled wave analysis, electromagneticbandgap, photonic bandgap, asymptotic boundary condition,impedance boundary condition, spectral domain method,homogenisation
3
Tharp, Jeffrey Scott. "DESIGN AND DEMONSTRATION OF MEANDERLINE RETARDERS AT INFRARED FREQUENCIES." Doctoral diss., University of Central Florida, 2007. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2813.
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Meanderline structures are widely used as engineered birefringent materials for waveplates and retarders at radiofrequencies, and have been previously demonstrated at frequencies up to 90 GHz in the millimeter-wave band. In this dissertation, we present results related to the modeling, fabrication, and experimental characterization of meanderlines across the range from 30 to 100 THz, in the long-wave and mid-wave infrared bands. Specific issues addressed in these new designs include spectral dispersion and angular dependence of the retardance, as well as axial ratio and throughput. The impact resulting from the infrared properties of the metals and dielectrics is explicitly included throughout. Several novel applications are identified, including integrated circular polarizers, reflective waveplates, and large-area polarization tags.Ph.D.
Optics and Photonics
Optics and Photonics
Optics PhD
4
Ullah, Irfan. "Measuring and filtering microwave radiations using frequency selective surface through energy saving glass." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2012. https://ro.ecu.edu.au/theses/480.
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This thesis presents the results of our investigation into the measurement and filtering of microwave radiation, and the subsequent development of a microwave reduction solution for modern building architecture utilising Energy Saving Glass (ESG), in conjunction with Frequency Selective (FSS) surfaces through which useful signals can be filtered. In the investigation, radiation power density levels arising from the three common microwave sources (radio base stations, mobile phones, and microwave ovens) were measured, and the results were compared with the standards provided by the Australian Radiation Protection and Nuclear Safety Agency. For the radio base stations, the relationship between radiation intensity levels and the important location parameters at the measurement point, e.g., line of sight, distance and elevation, are discussed in detail. Our results show that locations having the same elevation level as the RBS receive higher level of radiation, compared to those locations not at the same level. Power density of the radiation from microwave ovens was measured at various distances and angles. The results indicate that most of the radiation is emitted through the main door of the ovens, with the doors normally being assembled utilising simple float glass. ESG was found to have desirable radiation attenuating characteristics, and was identified as an effective replacement for float glass in microwave oven doors. In our investigation of the third potentially hazardous source of microwave radiation, the mobile handset, measurements were carried out in order to analyse power density levels during both call and idle times. Our results confirm that some handsets do not change power level, while others use higher power to communicate with the base station during a call. It is our recommendation that the manufacturers label each handset with the specific transmission power level in order to provide users with the relevant information. The conclusions drawn from our investigations lead us to recommend that ESG be used in buildings close to RBS, so that the levels of unnecessary radiation are reduced. However, useful signals would still be transmitted by utilising the dual bandpass FSS filters designed as part of this work. We designed two distinct models of bandpass FSS filters on hard coated ESG. The first filter that we designed will block microwave signals coming from weather radar, personal communication devices, power transmission lines and emergency service radios, while transmitting useful UMTS and Wi-Fi signals; minimising the radiation impact. Only 7.30% of the coating area of the glass was removed to enable transmission in the U850 and U2100 frequency bands. The second design requires the removal of 12.35% of the coating area to enable transmission in the U800, U850, U1900 and U2100 frequency bands. Simulation results for the two designs show stable frequency responses for both TE and TM polarisations at normal and oblique incident angles, with attenuation's below 10 dB within the passbands. Parametric studies on geometrical dimensions, substrate permittivity, and thickness help clarify the effects of these parameters upon the overall performance of FSS on hard coating ESG, and help the process of FSS design optimisation.
5
Kohlgraf, Dana C. "Design and testing of a frequency selective surface (FSS) based wide-band multiple antenna system." Connect to this title online, 2005. http://hdl.handle.net/1811/323.
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Thesis (Honors)--Ohio State University, 2005.Title from first page of PDF file. Document formattted into pages: contains ix, 54 p.; also includes graphics. Includes bibliographical references (p. 54). Available online via Ohio State University's Knowledge Bank.
6
Hill, Roger Alan. "The design of a dual band frequency selective surface and the effect of perturbing the elements and the interelement spacing." The Ohio State University, 1991. http://rave.ohiolink.edu/etdc/view?acc_num=osu1345127869.
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Niembro, Martin Alejandro. "Conception et développement de supports imprimables souples pour filtrage et adaptation des ondes électromagnétiques radiofréquences." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAT062.
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Les communications sans fil sont de plus en plus présentes dans notre quotidien, et avec elles, les ondes électromagnétiques qui leurs sont associées. Cela a créé un besoin de produits permettant de contrôler la portée du réseau, pour des raisons de sécurité de données, d'augmentation de débit en cas d'interférences avec d'autres réseaux, ou bien pour des raisons sanitaires. A l'inverse, dans d'autres cas, l'amélioration de la transmission de ces ondes est recherchée. Par exemple, dans les bâtiments de nouvelle construction ou rénovées, l'installation de vitrages à isolation renforcée permet d'avoir des bâtiments plus performantes au niveau thermique. Malheureusement, ces vitrages bloquent également les radiofréquences, dont notamment les signaux de téléphonie mobile. L'objectif de la thèse est la conception et le développement de structures filtrantes imprimées sur substrat souple. Dans un premier temps, des solutions de filtrage sélectif coupe bande sont proposées afin d'empêcher autant que possible la transmission d'ondes électromagnétiques, par exemple celles du WiFi entre les pièces d'un bâtiment. Dans un deuxième temps, une solution permettant d'améliorer la transmission des ondes électromagnétiques au travers des vitrages thermiques est proposée. Outre ces études, un système de caractérisation permettant de caractériser finement ces structures FSS a été développé lors de ces travaux de thèseNowadays wireless communication systems are more and more present in our lives, and with them, electromagnetic waves associated to them. A need of products capable to control the range of the network has appeared, for data security reasons, for data rate increase in case of network interferences or for health reasons. On the opposite, in other cases, improving the transmission of these waves is desired. For instance, in new construction or renovated buildings, energy saving windows allows having more efficient buildings thermal speaking. Unfortunately, those windows also block radiofrequencies, including mobile phone signals. The aim of this thesis is the design and development of filtering structures printed on flexible substrate. First, stop band selective filtering solutions are proposed in order to block as much as possible transmission waves, for instance, WiFi in between different rooms of the same building. Secondly, a solution to improve electromagnetic wave transmission through energy saving windows is proposed. In addition to these studies, a characterization system for testing these FSS structures has been developed during this thesis work
8
Van, den Berg Monique. "Thin linear-to-circular polarizers with enhanced bandwidth." Diss., University of Pretoria, 2018. http://hdl.handle.net/2263/64557.
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Circular polarization is valuable for many electromagnetic radiation applications such as wireless and satellite communication, radars, RFID, global positioning systems, etc. Many efforts have been made to manipulate and control polarization by using linear-to-linear or linear-to-circular transmission or reflection polarization converters. Most of the existing linear-to-circular single-layer polarizers have been found to be narrowband. Some attempts have been made to improve the bandwidth of these polarizers including using multiple layered structures at the expense of a bulkier device. There was, however, still a requirement for thin single-layer linear-to-circular polarizers with enhanced bandwidth. The purpose of this research was to design two thin single-layer linear-to-circular polarizers, one for transmission and the other for reflection, with enhanced bandwidth.
A thin single-layer linear-to-circular transmission polarizer with a 3 dB axial ratio bandwidth of 34% is presented. The bandwidth of this polarizer is significantly better than that of previously published polarizers of the same type. The unit cell of the polarizer consists of an I-shaped strip and a perpendicular linear strip printed on the one side of a thin dielectric substrate and two additional capacitive coupling strips printed on the other side of the substrate. Experimental results were found to agree well with the simulated results.
A thin single-layer reflective linear-to-circular polarizer with a 3 dB axial ratio bandwidth of 57% is also presented. The unit cell of the polarizer consists of an I-shaped strip and a perpendicular linear strip printed on the one side of a substrate and a ground plane on the other side of the substrate. Experimental results for this polarizer were also found to agree well with the simulated results.Dissertation (MEng)--University of Pretoria, 2018.
Electrical, Electronic and Computer Engineering
MEng
Unrestricted
9
Cure, David. "Reconfigurable Low Profile Antennas Using Tunable High Impedance Surfaces." Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4659.
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This dissertation shows a detailed investigation on reconfigurable low profile antennas using tunable high impedance surfaces (HIS). The specific class of HIS used in this dissertation is called a frequency selective surface (FSS). This type of periodic structure is fabricated to create artificial magnetic conductors (AMCs) that exhibit properties similar to perfect magnetic conductors (PMCs). The antennas are intended for radiometric sensing applications in the biomedical field. For the particular sensing application of interest in this dissertation, the performance of the antenna sub-system is the most critical aspect of the radiometer design where characteristics such as small size, light weight, conformability, simple integration, adjustment in response to adverse environmental loading, and the ability to block external radio frequency interference to maximize the detection sensitivity are desirable.
The antenna designs in this dissertation are based on broadband dipole antennas over a tunable FSS to extend the usable frequency range. The main features of these antennas are the use of an FSS that does not include via connections to ground, their low profile and potentially conformal nature, high front-to-back radiation pattern ratio, and the ability to dynamically adjust the center frequency. The reduction of interlayer wiring on the tunable FSS minimizes the fabrication complexity and facilitates the use of flexible substrates.
This dissertation aims to advance the state of the art in low profile tunable planar antennas. It shows a qualitative comparison between antennas backed with different unit cell geometries. It demonstrates the feasibility to use either semiconductor or ferroelectric thin film varactor-based tunable FSS to allow adjustment in the antenna frequency in response to environment loading in the near-field. Additionally, it illustrates how the coupling between antenna and HIS, and the impact of the varactor losses affect the antenna performance and it shows solutions to compensate these adverse effects. Novel hybrid manufacturing approaches to achieve flexibility on electrically thick antennas that could be transitioned to thin-film microelectronics are also presented.
The semiconductor and ferroelectric varactor-based tunable low profile antennas demonstrated tunability from 2.2 GHz to 2.65 GHz with instantaneous bandwidths greater than 50 MHz within the tuning range. The antennas had maximum thicknesses of λ/45 at the central frequency and front to back-lobe radiation ratios of approximately 15dB. They also showed impedance match improvement in the presence of a Human Core Model (HCM) phantom at close proximity distances of the order of 10-20 mm. In addition, the use of thin film ferroelectric Barium Strontium Titanate (BST) varactors in the FSS layer enabled an antenna that had smaller size, lower cost and less weight compared to the commercially available options.
The challenging problems of fabricating robust flexible antennas are also addressed and novel solutions are proposed. Two different types of flexible antennas were designed and built. A series of flexible microstrip antennas with slotted grounds which demonstrated to be robust and have 42% less mass than typically used technologies (e.g., microstrip antennas fabricated on Rogers® RT6010, RT/duroid® 5880, etc.); and flexible ferroelectric based tunable low profile antennas that showed tunability from 2.42 GHz to 2.66 GHz using overlapping metallic plates instead of a continuous ground plane. The bending test results demonstrated that, by placing cuts on the ground plane or using overlapping metallic layers that resemble fish scales, it was possible to create highly conductive surfaces that were extremely flexible even when attached to other solid materials. These new approaches were used to overcome limitations commonly encountered in the design of antennas that are intended for use on non-flat surfaces.
The material presented in this dissertation represents the first investigation of reconfigurable low profile antennas using tunable high impedance surfaces where the desired electromagnetic performance as well as additional relevant features such as robustness, low weight, low cost and low complexity were demonstrated.
10
隆彦, 吉田, and Takahiko Yoshida. "Frequency selective surfaceを利用した電磁波吸収体の設計と応用に関する研究." Thesis, https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB13071688/?lang=0, 2018. https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB13071688/?lang=0.
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García-Verdugo, Zuil Ana, and Martín Amanda Herrero. "Additive manufacturing and radio frequency filters : A case study on 3D-printing processes, postprocessing and silver coating methods." Thesis, KTH, Industriell produktion, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-280572.
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Additive manufacturing (AM) is an attractive way to shorten development time, reduce product weight and allow the manufacturing of more complex products than by conventional manufacturing processes. The problem arises when the previous traditional manufacturing requirements need to be fulfilled by AM as well as the volume production capability. This investigation is done together with Ericsson to evaluate the possibilities of the different AM technologies, post-processing methods and silver coating processes to guarantee the specifications of radiofrequency (RF) filters. Here, minimal RF signal insertion losses are targeted. Since insertion losses are dependent on surface roughness, surface smoothness is sought as well. Ericsson simulation software uses correction factors to account for surface roughness, however there are some inconsistencies between the simulated and actual surface roughness that is allowed in the parts. In AM parts, surface roughness is not easy to control since it depends on parameters related to feedstock, process and machine properties. Commonly, most AM components do not comply with requirements of lower surface roughness values. Therefore, parts need to be smoothened before silver plated; this step is necessary to ensure the electrical conductivity in this specific application. These finishing processes add costs to the final product and increase time to market. Firstly, a comprehensive study was carried out to better understand the landscape of AM technologies, postprocessing and silver coating methods. Secondly, the different processes are assessed with the help of selection matrices, considering the products requirements. The components to print are two RF filters with different shapes and dimensions but similar requirements. The CAD design is modified depending on each AM process and directly affects the results. Afterwards, the design of an experimental plan is carried out; the number of samples of each part comparing AM technologies, feedstock, different suppliers (3D printing and post-processing) is obtained. Due to budget and time restrictions, the parts were printed using Multi Jet Fusion and Selective Laser Melting processes. After printing, tolerances and surface roughness were measured. This thesis results in the selection of suitable AM technologies and post-processing methods for RF filters. For MJF printed cavities at 0˚, 30˚ and 90˚ orientation, the best results for this application are obtained at 30˚ providing a good balance between sharp detail and smooth surfaces. In the case of SLM, waveguides are printed at 0˚ and 30˚. 30˚ waveguides present lower surface roughness values than the 0˚ ones as inner support material is needed at 0˚ orientation. SLM cavities were printed at 30˚ in seek of asymmetry between faces, resulting in higher surface roughness in the downfacing face.
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Euler, Mattias. "Transpolarizing frequency selective surfaces." Thesis, Queen's University Belfast, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.534744.
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Chang, Teck Keng. "Active frequency selective surfaces." Thesis, University of Kent, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.281659.
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Cox, Gavin J. "Techniques for pattern control of a dielectric rod antenna suitable for use in mobile communications." Thesis, Loughborough University, 2002. https://dspace.lboro.ac.uk/2134/12693.
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This thesis describes the development of antennas suitable for mobile coinmunication systems based on a dielectric rod antenna fed from circular waveguide. Pattern control of the antenna is implemented using a combination of Frequency Selective Surface (FSS) elements and metallic endcaps placed on the antenna Both linear and circular polarised feeds have been made for these antennas to ensure they are suitable for a wide range of applications. The suitability of the dominant and next, higher order, waveguide mode were investigated and conclusions drawn as to their suitability for this type of antenna. The antennas were extensively modelled using a commercial TLM based solver and the results of these simulations were compared to the comprehensive set of antenna pattern measurements and S-parameter measurements obtained for the prototype antennas.
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Yildirim, Egemen. "Development Of Multi-layered Circuit Analog Radar Absorbing Structures." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614314/index.pdf.
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A fast and efficient method for the design of multi-layered circuit analog absorbing structures is developed. The method is based on optimization of specular reflection coefficient of a multi-layered absorbing structure comprising of lossy FSS layers by using Genetic Algorithm and circuit equivalent models of FSS layers. With the introduced method, two illustrative absorbing structures are designed with -15 dB reflectivity for normal incidence case in the frequency bands of 10-31 GHz and 5-46 GHz, respectively. To the author&rsquos knowledge, designed absorbers are superior in terms of frequency bandwidth to similar studies conducted so far in the literature. For broadband scattering characterization of periodic structures, numerical codes are developed. The introduced method is improved with the employment of developed FDTD codes to the proposed method. By taking the limitations regarding production facilities into consideration, a five-layered circuit analog absorber is designed and manufactured. It is shown that the manufactured structure is capable of 15 dB reflectivity minimization in a frequency band of 3.2-12 GHz for normal incidence case with an overall thickness of 14.2 mm.
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Brito, Davi Bibiano. "Metamaterial inspired improved antennas and circuits." Universidade Federal do Rio Grande do Norte, 2010. http://repositorio.ufrn.br:8080/jspui/handle/123456789/15152.
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Metamaterials exhibiting negative refraction have attracted a great amount of attention in recent years mostly due to their exquisite electromagnetic properties. These materials are artificial structures that exhibit characteristics not found in nature. It is possible to obtain a metamaterial by combining artificial structures periodically. We investigated the unique properties of Split Ring Resonators, High impedance Surfaces and Frequency Selective Surfaces and composite metamaterials. We have successfully demonstrated the practical use of these structures in antennas and circuits. We experimentally confirmed that composite metamaterial can improve the performance of the structures considered in this thesis, at the frequencies where electromagnetic band gap transmission takes place
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Höhn, Tomáš. "Modelování kmitočtově selektivních povrchů v programu COMSOL Multiphysics." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2008. http://www.nusl.cz/ntk/nusl-217463.
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Metoda konečných prvků implementovaná v programu COMSOL Multiphysics je využívána k analýze tzv. free-standing kmitočtově selektivních povrchů ve 3D. Tyto modely jsou následně doplněny o periodické okrajové podmínky. Dále jsou free-standing povrchy doplněny o vrstvy dielektrika a je zkoumán jejich vliv na modul činitele odrazu. V analytické části jsou vyhodnoceny vlivy počtu elementů diskretizační mřížky na přesnost výsledku a délku výpočtů. Výsledky jsou srovnávány vzhledem k výsledkům uvedeným v literatuře [5]. V závěrečné části práce je vysvětlen postup při generování m-file pro obdélníkový element a použití globálního optimalizačního algoritmu PSO, který automaticky upravuje rozměry vodivého motivu tak, aby bylo dosaženo průběhu modulu činitele odrazu podle požadovaného průběhu.
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Sanz, Fernandez Juan Jose. "Frequency selective surfaces for Terahertz applications." Thesis, University of Edinburgh, 2012. http://hdl.handle.net/1842/7648.
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This thesis presents both theoretical and experimental investigations of the performance and capabilities of frequency selective surfaces (FSS) applied at THz frequencies. The aim is to explore and extend the use of FSS, traditionally limited to microwave frequencies, towards the THz regime of the spectrum, where interesting applications such as imaging, sensing and communications exist. The contribution of this work lies in three main areas within the scope of THz FSS, namely, performance, prototyping and applications. Unlike microwave FSS where extensive research has been performed to evaluate the performance of different FSS designs, particular problems arise at THz frequencies, significantly, the ohmic losses. While a few notable studies can be found on the issue of ohmic losses, part of this thesis investigates, for the first time, the power dissipation due to the presence of both ohmic and dielectric losses, in relation to the power stored in the vicinity of the FSS, the currents induced in the elements of the array and the array’s terminal impedance. By doing so, a better understanding of the performance of THz FSS has been given in terms of their quality factor, allowing for design guidelines previously unavailable. In order to demonstrate multiband operation experimentally, a novel fabrication process has been designed and developed to manufacture capacitive or dipole-based THz FSS on a dielectric layer. Dry deep-reactive ion etching has been employed in order to avoid the use of wet etching to provide better control of etch characteristics. Various FSS operating around 15THz have been demonstrated experimentally. In addition, THz FSS have been investigated theoretically in the realm of three different applications, namely, multiband operation, sensing capability and reconfigurability. Multiband characteristics using single-screen FSS have been achieved by perturbed dipole FSS exhibiting up to four resonances due to the excitation of even and odd current modes. After studying the near-fields in perturbed FSS, it has been found that this type of FSS represent a very attractive candidate for sensing applications due to the revealed near-field enhancement phenomena related to the excitation of the odd mode, where currents flow in opposite directions. Finally, a novel tunability approach to reach frequency reconfigurability by varying the near-field coupling between two closely spaced layers in a dual-layer configuration has been proposed. A MEMS movable four-arm membrane has been suggested to vary the distance between the two layers mechanically, leading to the frequency tuning effect. This approach has been shown to be particularly suitable for THz frequencies, and has been applied to demonstrate theoretically tunable FSS and other periodic structures, such as artificial magnetic conductors and dielectric gratings.
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Silva, Segundo Francisco Carlos Gurgel da. "An?lise e projeto de superf?cies seletivas em frequ?ncia multibanda e/ou banda larga." Universidade Federal do Rio Grande do Norte, 2014. http://repositorio.ufrn.br:8080/jspui/handle/123456789/15508.
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Frequency selective surfaces (Frequency Selective Surface - FSS) are often used in various applications in telecommunications. Some of these applications may require that these structures have response with multiple resonance bands. Other applications require that the FSS response have large frequency range, to meet the necessary requirements. FSS to design with these features there are numerous techniques cited in the scientific literature. Thus, the purpose of this paper is to examine some common techniques such as: Overlap of FSS; Elements combined; Elements Elements convolucionados and fractals. And designing multiband FSS and / or broadband selecting simple ways in terms of construction and occupy the smallest possible space, aiming at practical applications. Given these requirements, three projects FSS were performed: a technology applied to IEEE 802.11 a/b/g/n and two projects for application in UWB. In project development, commercial software Ansoft DesignerTM and experimental results were satisfactory was used
Superf?cies seletivas em frequ?ncia (Frequency Selective Surface - FSS) s?o usadas frequentemente em diversas aplica??es em telecomunica??es. Algumas dessas aplica??es podem exigir que essas estruturas tenham resposta com m?ltiplas bandas de resson?ncia. Outras aplica??es exigem que as FSS tenham resposta em faixa larga de frequ?ncia, para atender aos requisitos necess?rios. Para projetar uma FSS com essas caracter?sticas existem in?meras t?cnicas citadas na literatura cient?fica. Assim, o prop?sito deste trabalho ? analisar algumas t?cnicas utilizadas tais como: Sobreposi??o de FSS; Elementos combinados; Elementos convolucionados e Elementos fractais. E projetar FSS multibanda e/ou banda larga selecionando maneiras simples em termos de constru??o e que ocupem o menor espa?o poss?vel, visando aplica??es pr?ticas. Tendo em vista estes requisitos, foram realizados tr?s projetos de FSS: um aplicado a tecnologia IEEE 802.11 a/b/g/n e dois projetos para aplica??o em UWB. No desenvolvimento dos projetos, foi utilizado o software comercial Ansoft DesignerTM e os resultados experimentais se mostraram satisfat?rios
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Oliveira, Phelipe Sena. "Desenvolvimento de uma nova t?cnica para otimiza??o de circuitos planares inspirada no comportamento social das aranhas." PROGRAMA DE P?S-GRADUA??O EM ENGENHARIA EL?TRICA E DE COMPUTA??O, 2017. https://repositorio.ufrn.br/jspui/handle/123456789/24644.
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Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico (CNPq)
As novas configura??es de dispositivos e circuitos de micro-ondas resulta em aumento de complexidade nos processos de desenvolvimento, particularmente nos casos de s?ntese. Antenas e superf?cies seletivas de frequ?ncia (Frequency Selective Surface - FSS) s?o estruturas muito importantes nos sistemas de comunica??es, que podem ser otimizadas pela atua??o dos algoritmos bioinspirados. Geralmente, para que os algoritmos bioinspirados auxiliem na otimiza??o dessas estruturas ? necess?ria a implementa??o de t?cnicas de an?lise num?rica como o M?todo dos Momentos ou Elementos Finitos. Diante da dificuldade de modelagem das t?cnicas descritas, ? comum a utiliza??o de uma fun??o de estima??o, como as Redes Neurais Artificiais, para substituir a an?lise num?rica. Embora encontre solu??es desejadas, as estima??es s?o realizadas ap?s um processo de treinamento efetuado atrav?s de uma base de dados. Cada estrutura de antena ou FSS exige uma base de dados espec?fica. Este trabalho prop?e uma t?cnica de otimiza??o baseado na utiliza??o de um algoritmo bioinspirado e um framework que realiza a integra??o do algoritmo ao software comercial ANSYS HFSS. O prop?sito ? realizar as simula??es das poss?veis solu??es durante a execu??o do algoritmo bioinspirado, e com isso, evitar o uso de uma base de dados, e assim, tornar a t?cnica eficiente e flex?vel com rela??o ?s altera??es nas estruturas de antenas ou FSS. Outro objetivo original deste trabalho ? a utiliza??o do algoritmo Social Spider Optimization ? SSO para a solu??o de problemas na ?rea de eletromagnetismo aplicado. Para comprovar a efic?cia da t?cnica proposta alguns projetos de antena e FSS s?o otimizados atrav?s de varia??es em seus par?metros estruturais. Os resultados obtidos na otimiza??o dos projetos dos circuitos s?o comparados com outras t?cnicas, tendo sido observado uma boa concord?ncia.
The new settings for devices and microwaves circuits result in an increase of complexity in the processes of development, specially in regards to the process of synthesis. Antennas and Frequency Selective Surfaces (FSS) are primordial in communication systems. Alternatively, these structures may be optimized through the usage of bio-inspired algorithms. Generally, in order for the bio-inspired algorithms to assist in the optimization of FSS structures, it is necessary to implement several numerical analysis techniques, such as the method of moments or finite elements. Because of the difficulty to model such methods, it has been turned common the usage of a point estimation function, such as artificial neural networks, to substitute the numerical analysis. Although these procedures end up encountering desirable solutions, the estimations are done after a training process conducted through a database. Additionally, every FSS antenna demands a specific database. This work proposes an optimization technique that relies on the usage of a bio-inspired algorithm and a framework (that provides the integration between the algorithm and the commercial software ANSS HFSS). The purpose of the work is to do simulations of possible solutions during the execution of the bio-inspired algorithm; therefore, avoiding the usage of the database; and so, make the technique flexible and efficient in relation to altering the antennas? structures or FSS. Furthermore, another objective of this work is the usage of the algorithm, namely Social Spider Optimization - SSO in the search for solutions in the field of applied electromagnetism. In order to prove the efficiency of the proposed techniques, some FSS? and antennas? projects are optimized through the variation of their structural parameters. In conclusion, the results that were obtained through the procedures previously shown, are compared to other techniques, resulting in a satisfying agreement rate.
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Chia, Yan Wah. "Radiation from curved (conical) frequency selective surfaces." Thesis, Loughborough University, 1993. https://dspace.lboro.ac.uk/2134/7200.
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The thesis deals with the analysis of a microwave Frequency Selective Surface (FSS) on a conical dielectric radome illuminated by a feed hom located at the base. Two approaches have been adopted to solve this problem. The first approach is to calculate the element currents under the assumption that the surface is locally flat. Consequently, the element current at that locality can be determined by employing Floquet modal analysis. The local incidence has been modelled from the radiation pattern of the source or the aperture fields of the feed. Three types of feed model were used to account for the field illumination on the radome. The transmitted fields from the curved surface are obtained from the sum of the radiated fields due to the equivalent magnetic and electric current sources distributed in each local unit cell of the conical surface. This method treats the interaction of neighbouring FSS elements only. In the second approach the curvature is taken into account by dividing the each element into segments which conform to the curved surface. An integral formulation is used to take into account the interaction of all the elements. The current source in each FSS element from the formulation is solved using the method of moments (MOM) technique. A linear system of simultaneous equations is obtained from the MOM and has been solved using elimination method and an iterative method which employs conjugate gradients. The performance of both methods has been compared with regard to the speed of computations and the memory storage capability. New formulations using quasi static approximations have been derived to account for thin dielectric backing in the curved aperture FSS analysis. Computer models have been developed to predict the radiation performance of the curved(conical) FSS. Experiments were performed in an anechoic chamber where the FSS cone was mounted on a jig resting on a turntable. The measuring setup contained a sweep oscillator that supplied power to a transmitting feed placed at the base of the cone. Amplitude and phase values of the far field radiation pattern of the cone were measured with the aid of a vector network analyser. Cones with different dimensions and FSS element geometries were constructed and the measured transmission losses and radiation patterns compared with predictions.
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Lockyer, David S. "Reconfigurable and closely coupled frequency selective surfaces." Thesis, Loughborough University, 1999. https://dspace.lboro.ac.uk/2134/6828.
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The performance of a planar Frequency Selective Surface (FSS) cannot be changed or adapted once the manufacturing process has been completed. In practice, however, it would be advantageous to be able to do so, in order to increase flexibility of performance in multiband systems for example. This thesis examines a novel electromagnetict echniquet hat has beend eveloped,w hereby the frequencya nd/or the angular response of FSS's can be tuned in situ over a wide range of frequencies and/or steering angles. The technique employed is passive and relies upon the displacemento f closely separated( and therefore closely coupled) arrays with respect to each other. A global loading of the array results so that the reconfigurable FSS (RFSS) will produce a broadband and/or multibeam response without altering the individual array design. The experience and understanding gained during this work was subsequently used to produce FSS responses of extreme angular stability. In this case a static, double layer structure has been used to make use of the high coupling between the layers i.e. two FSS's printed on a single dielectric substrate to form a close coupled FSS (CCFSS). It was found that the coupling between the two layers was highly dependent on the relative displacement between arrays. This displacement is introduced statically during the manufacture of the FSS. The cases described use two identical layers. A further development of this concept makes use of complementary conducting and aperture elements giving rise to a complementary FSS (CFSS). The CFSS is also manufactured on a common dielectric and produces ultra stable resonant frequencies for both TE and TM oblique incidences. Theoretical verification of the measured results has been achieved, and the measured and predicted results agreed very closely. Modal analysis, using a novel coupled integral equation technique, has been used to predict the response of the RFSS and CFSS. The correlation between the predicted and measured transmission response of the RFSS was very good and it was discovered that operational stability of the bandwidths and band spacing ratios were significantly improved over conventional static FSS.
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Dickie, R. J. "Substrateless multilayer millimetre wave frequency selective surfaces." Thesis, Queen's University Belfast, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.411105.
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El-Sheikh, Abdel Nasser Ahmed. "Advances in the design of frequency selective surfaces." Thesis, University of Kent, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303156.
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Cross, Lee W. "Design of Microwave Front-End Narrowband Filter and Limiter Components." Thesis, The University of Toledo, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=3588122.
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This dissertation proposes three novel bandpass filter structures to protect systems exposed to damaging levels of electromagnetic (EM) radiation from intentional and unintentional high-power microwave (HPM) sources. This is of interest because many commercial microwave communications and sensor systems are unprotected from high power levels. Novel technologies to harden front-end components must maintain existing system performance and cost. The proposed concepts all use low-cost printed circuit board (PCB) fabrication to create compact solutions that support high integration.
The first proposed filter achieves size reduction of 46% using a technology that is suitable for low-loss, narrowband filters that can handle high power levels. This is accomplished by reducing a substrate-integrated waveguide (SIW) loaded evanescent-mode bandpass filter to a half-mode SIW (HMSIW) structure. Demonstrated third-order SIW and HMSIW filters have 1.7 GHz center frequency and 0.2 GHz bandwidth. Simulation and measurements of the filters utilizing combline resonators prove the underlying principles.
The second proposed device combines a traditional microstrip bent hairpin filter with encapsulated gas plasma elements to create a filter-limiter: a novel narrowband filter with integral HPM limiter behavior. An equivalent circuit model is presented for the ac coupled plasma-shell components used in this dissertation, and parameter values were extracted from measured results and EM simulation. The theory of operation of the proposed filter-limiter was experimentally validated and key predictions were demonstrated including two modes of operation in the on state: a constant output power mode and constant attenuation mode at high power. A third-order filter-limiter with center frequency of 870 MHz was demonstrated. It operates passively from incident microwave energy, and can be primed with an external voltage source to reduce both limiter turn-on threshold power and output power variation during limiting. Limiter functionality has minimal impact on filter size, weight, performance, and cost.
The third proposed device demonstrates a large-area, light-weight plasma device that interacts with propagating X-band (8-12 GHz) microwave energy. The structure acts as a switchable EM aperture that can be integrated into a radome structure that shields enclosed antenna(s) from incident energy. Active elements are plasma-shells that are electrically excited by frequency selective surfaces (FSS) that are transparent to the frequency band of interest. The result is equivalent to large-area free-space plasma confined in a discrete layer. A novel structure was designed with the aid of full-wave simulation and was fabricated as a 76.2 mm square array. Transmission performance was tested across different drive voltages and incidence angles. Switchable attenuation of 7 dB was measured across the passband when driven with 1400 Vpp at 1 MHz. Plasma electron density was estimated to be 3.6 × 10 12 cm-3 from theory and full-wave simulation. The proposed structure has potential for use on mobile platforms.
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Hossainzadeh, Bezminabady A. "Analysis and design of multilayer frequency selective surfaces." Thesis, Loughborough University, 1997. https://dspace.lboro.ac.uk/2134/12360.
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Structures that include more than one layer of Frequency Selective Surfaces (FSS) are an attractive feature in applications with stringent performance requirements. They provide extra flexibility with regard to the adjustment of the transmission responses which can in principle be insensitive to angle of incidence because of the increased bandwidth. This thesis deals with computer simulation and experimental assessment of a variety of multilayer FSS structures. The plane wave vector modal analysis technique is adapted for analysing the scattering from these multilayer FSS structures. The novelty in the plane wave modal analysis method lies in the fact that they can be applied to arbitrary lattice and element geometries. A novel super-resolution approach of analysing the scattering from FSS in cascade, with arbitrary lattice geometries of the two arrays is outlined. These type of structures exhibit multiresonant responses in a controlled manner. The problem of assigning different lattice geometries to the structure is addressed here by assigning the periodic fields adjacent to the arrays a common (or mutual) periodicity and by employing the convolution theorem to the modal (Floquet) sets that expands the tangential fields in each array. As a result, the spectral components of the Floquet mode coefficients from the various adjacent arrays are related to those of the common periodicity by means of a correlation function. This correlation function enables the spectral components of the Floquet mode sets expanding the tangential fields from any two adjacent arrays to be super-resolved from those of their common periodicity set. Once the convolution has been executed, application of electromagnetic boundary conditions are utilised, thus obtaining the coupled electric field integral equations. These integral equations relate the spectrums of the surface current densities to the various Floquet mode coefficients. The integral equations are in turn solved by the Method of Moment (MoM) technique for the unknown current coefficients from which the unknown transmission and reflection coefficients from the entire structure are obtained. A major assumption that is made in this technique for assigning a common periodicity lattice is that the ratio of lattice periodicities of any two adjacent arrays must be a rational number. The importance of the proposed technique lies in unlocking the complexities that exist when the scattered Aoquet modal coefficients from the arrays are related to the spectral components of the currents induced on the surfaces of the arrays, in the integral equation formulation. Furthermore, the proposed approach offers a computational advantage when applied to multilayer FSS structures, as it is invariant to the distance separating the arrays. A computer model based on this technique is developed for obtaining the prediction results. Various double layer FSS structures with arbitrary element types and lattice geometries of the arrays and with variable separation distances between the two layers are studied. The plane wave transmission coefficients of these multiresonant structures are computed with a v1ew to predict their radiation parameters. Extensive measurements are performed by using a purpose built experimental jig for mounting the structures, in an indoor anechoic chamber. The validity of the theoretical model is assessed by comparison with measurements from a variety of multilayer structures.
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Liu, Youcheng. "Analysis of frequency selective surfaces with ferrite substrates." Doctoral diss., University of Central Florida, 1996. http://digital.library.ucf.edu/cdm/ref/collection/RTD/id/362.
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University of Central Florida College of Engineering ThesisFrequency selective surfaces (FSS) have numerous applications in several microwave and optical systems. In this work, instead of traditional dielectric substrates, ferrite substrates are used under different dc bias conditions.
Ph.D.
Doctorate;
Department of Electrical and Computer Engineering
Engineering
Electrical and Computer Engineering
115
viii, 115 leaves, bound : ill. ; 28 cm.
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Barreto, Edwin Luize Ferreira. "Estudo de Superf?cies Seletivas de Frequ?ncia com o Uso de Intelig?ncia Computacional." Universidade Federal do Rio Grande do Norte, 2012. http://repositorio.ufrn.br:8080/jspui/handle/123456789/15463.
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Previous issue date: 2012-07-20Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior
The main objective of this work is to optimize the performance of frequency selective surfaces (FSS) composed of crossed dipole conducting patches. The optimization process is performed by determining proper values for the width of the crossed dipoles and for the FSS array periodicity, while the length of the crossed dipoles is kept constant. Particularly, the objective is to determine values that provide wide bandwidth using a search algorithm with representation in bioinspired real numbers. Typically FSS structures composed of patch elements are used for band rejection filtering applications. The FSS structures primarily act like filters depending on the type of element chosen. The region of the electromagnetic spectrum chosen for this study is the one that goes from 7 GHz to 12 GHz, which includes mostly the X-band. This frequency band was chosen to allow the use of two X-band horn antennas, in the FSS measurement setup. The design of the FSS using the developed genetic algorithm allowed increasing the structure bandwidth
Este trabalho tem como objetivo principal efetuar a otimiza??o do desempenho de estruturas de superf?cies seletivas de frequ?ncia FSS (Frequency Selective Surface), com patches condutores na forma de dipolos em cruz. A otimiza??o foi realizada atrav?s da identifica??o de valores ?timos para a largura do dipolo e a periodicidade do arranjo, considerando o valor do comprimento do dipolo fixo. Especificamente, objetiva-se determinar valores que permitam aumentar a largura de banda, utilizando um algoritmo de busca bioinspirado com representa??o em n?meros reais. As aplica??es t?picas de estruturas de FSS com patches condutores utilizam frequ?ncias selecionadas atrav?s das faixas de rejei??o. As estruturas de FSS funcionam basicamente como filtros dependendo do tipo de elemento escolhido. A regi?o do espectro eletromagn?tico escolhida para este estudo foi a faixa de 7 GHz a 12 GHz, que inclui basicamente a banda X. Essa regi?o do espectro eletromagn?tico foi escolhida para possibilitar a medi??o do dispositivo com a utiliza??o de antenas de abertura do tipo corneta, que operam na banda X. O projeto da FSS com a utiliza??o do algoritmo gen?tico GA (Genetic Algorithm) permitiu aumentar a largura de banda da estrutura
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Papantonis, Dimitrios Papantonis. "Tightly-Coupled Arrays with Reconfigurable Bandwidth." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1503046689468305.
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Chen, Wei Zhang Ruifeng. "Time- frequency- selective channel estimation of ofdm systems /." Philadelphia, Pa. : Drexel University, 2005. http://dspace.library.drexel.edu/handle/1860/616.
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Taylor, P. S. "Frequency selective surfaces and applications to the built environment." Thesis, University of Kent, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.590061.
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The research carried out and detailed in this thesis presents several techniques applied to frequency selective surfaces (FSS) with an emphasis on propagation control in the built environment. Issues are explored such as interference reduction and frequency reuse, security applications or propagation enhancement by reducing the effects of multi path and the wireless black spots or nulls that it produces. A band-stop active FSS (AFSS) has been designed operating in the WLAN band of 2.45GHz. The structure consists of annular ring. elements with PIN diodes as the semiconductor switches. The surface is two-state, being reflective with the diodes forward biased and transparent when zero biased. The design is single sided and includes an efficient distribution method of the de biasing by employing RP chokes. A prototype surface is constructed and its transmission response measured for a range of angles of electromagnetic wave incidence. A dual-band passive band-stop FSS is designed operating in the WLAN bands of 2.45GHz and 5GHz. The annular ring design introduces "traps" to FSS, where a trap is a parallel tuned circuit and behaves as a frequency selective switch, presenting a low or high impedance state depending upon the band of operation. Similarly the technique is applied to an annular slot design where the parallel tuned circuit is replaced with a series tuned circuit. For both designs prototype surfaces were constructed and evaluated for dual-band operation, with transmission response measurements carried out over a range of angles of electromagnetic wave incidence. A new AFSS structure known as the "phase plate" is introduced. A phase plate is a AFSS backed by a solid rear reflective surface spaced some distance away and modulated at a rate to modify wireless coverage nulls in enclosed environments, improving signal distribution in that space. A 2.45GHz experimental phase plate is constructed and evaluated, both by static phase shift measurements and observing its operation in a multi path environment with the successful filling of a wireless null. To demonstrate its performance a just discernible signal in the noise floor of the measurement receiver is brought some 20dB above it.
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Vardaxoglou, J. C. "Computer simulation of scattering from plane frequency selective surfaces." Thesis, University of Kent, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.354581.
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Trevithick, Jacob D. "Millimeter Wave Radar Object Detection Through Frequency Selective Surfaces." DigitalCommons@CalPoly, 2019. https://digitalcommons.calpoly.edu/theses/2077.
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Millimeter wave (mmWave) radar systems are a leading technology in autonomous vehicle object sensing. The radar’s ability to detect surrounding objects is critical to its performance. One method of increasing object detection performance is to enhance object visibility. Frequency selective reflectors can increase object visibility. This work examines the performance of a mmWave 77 GHz radar system developed by Texas Instruments in conjunction with frequency selective surfaces. Two bandpass frequency selective surfaces are designed and fabricated using a loaded cross aperture configuration to analyze their application to object detection. The chosen design frequencies are 8 GHz and 79 GHz. The frequency selective surfaces are designed and simulated in 3-D electromagnetic simulation software, High Frequency Structure Simulator (HFSS). The frequency selective surfaces are fabricated on 127μm thick FR4 dielectric. The 8 GHz frequency selective surface demonstrates bandpass center frequency at 8.12 GHz. The 8 GHz and 79 GHz frequency selective surface reflection characteristics are compared to a copper sheets with the same physical cross section as each respective design. Although different testing methodology is used for each design, both frequency selective surfaces demonstrate bandpass characteristics at their respective design frequencies.
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LANQUETIN, JEAN-PHILIPPE. "Analyse rigoureuse de surfaces selectives en frequence." Nice, 1991. http://www.theses.fr/1991NICE4514.
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Le but de cette these est l'analyse rigoureuse de la diffraction par un obstacle conducteur plan periodique, pour l'etude de ses proprietes en fonction de la frequence du rayonnement incident. Le champ electromagnetique diffracte est developpe en modes de floquet (harmoniques d'espace). La condition aux limites conduit a une equation fonctionnelle. Pour sa resolution, un programme base sur la methode des gradients conjugues a ete developpe. Ce logiciel permet l'etude des harmoniques d'espace d'ordres superieurs et fournit la courbe de reponse en frequence de l'obstacle
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Seman, F. Che. "Performance enhancement of Salisbury screen absorbers using frequency selective surfaces." Thesis, Queen's University Belfast, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.546026.
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Monacelli, Brian. "SPECTRAL SIGNATURE MODIFICATION BY APPLICATION OF INFRARED FREQUENCY-SELECTIVE SURFACES." Doctoral diss., University of Central Florida, 2005. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3534.
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It is desirable to modify the spectral signature of a surface, particularly in the infrared (IR) region of the electromagnetic spectrum. To alter the surface signature in the IR, two methods are investigated: thin film application and antenna array application. The former approach is a common and straightforward incorporation of optically-thin film coatings on the surface designated for signature modification. The latter technique requires the complex design of a periodic array of passive microantenna elements to cover the surface in order to modify its signature. This technology is known as frequency selective surface (FSS) technology and is established in the millimeter-wave spectral regime, but is a challenging technology to scale for IR application. Incorporation of thin films and FSS antenna elements on a surface permits the signature of a surface to be changed in a deterministic manner. In the seminal application of this work, both technologies are integrated to comprise a circuit-analog absorbing IR FSS. The design and modeling of surface treatments are accomplished using commercially-available electromagnetic simulation software. Fabrication of microstructured antenna arrays is accomplished via microlithographic technology, particularly using an industrial direct-write electron-beam lithography system. Comprehensive measurement methods are utilized to study the patterned surfaces, including infrared spectral radiometry and Fourier-transform infrared spectrometry. These systems allow for direct and complementary spectral signature measurements--the radiometer measures the absorption or emission of the surface, and the spectrometer measures its transmission and reflection. For the circuit-analog absorbing square-loop IR FSS, the spectral modulation in emission is measured to be greater than 85% at resonance. Other desirable modifications of surface signature are also explored; these include the ability to filter radiation based on its polarization orientation and the ability to dynamically tune the surface signature. An array of spiral FSS elements allows for circular polarization conditioning. Three techniques for tuning the IR FSS signature via voltage application are explored, including the incorporation of a pn junction substrate, a piezoelectric substrate and a liquid crystal superstrate. These studies will ignite future explorations of IR FSS technology, enabling various unique applications.Ph.D.
Other
Optics and Photonics
Optics
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Cahill, B. M. "Substrate integrated ferrite phase shifters and active frequency selective surfaces." Thesis, University of Kent, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.250325.
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Hussein, M. N. "Submillimeter, millimeter and microwave frequency selective surfaces, design and development." Thesis, University of Liverpool, 2018. http://livrepository.liverpool.ac.uk/3018441/.
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This dissertation presents new approaches to design and development of submillimeter, millimeter, and microwave frequency-selective surfaces (FSSs) having extensive applications in wireless communications and radar systems. The theory of the surfaces is introduced in Chapter 3 where a new approach to miniaturise the size of an FSS array element is presented by interconnecting array elements in one direction in a two-layer FSS structure. The top layer acts as an enhanced inductor while the bottom layer acts as a capacitor. The interconnection between adjacent array elements changes the equivalent circuit and produces a strong cross-layer capacitance, which lowers the resonant frequency significantly. The dimensions of the miniaturised FSS element are much smaller than the wavelength at the resonant frequency (periodicity << λ). Chapter 4 introduces a new methodology to design the FSS by maximizing the value of the capacitance between adjacent layers. The proposed structure offers three distinctive advantages: Firstly, the strong cross-layer capacitance makes the FSS element very compact. Secondly, for the proposed structure, the lower the profile, the stronger the cross-layer capacitance, and the lower the resonant frequency. This is unique to the proposed structure since the resonant frequency is usually higher for a lower profile than for traditional structures. Thirdly and most importantly, any external dielectric material attached to the FSS will not significantly affect the performance of the FSS due to this strong cross-layer capacitance. Chapter 5 introduces novel methodologies to design dual band spatial filters by using FSS periodic arrays composed of a bandpass and a bandstop element. The fabrication of the dual band filters is significantly simplified by using a single metal layer on a dielectric substrate. Chapter 6 introduces a new schematic to design a miniaturised high order bandpass FSSs (N ≥ 1), where N is the order of the FSS filter, with high performance with a flat in-band frequency response and fast roll-off is introduced. Two miniaturised resonant surfaces coupled by a non-resonant inductive layer are used to build the proposed FSSs. An FSS operating at around 3.8 GHz is designed to verify the method. The element size is smaller than 0.076λ×0.076λ for the proposed structure. This is significantly smaller than the element size of second-order FSSs designed using conventional approaches. The overall thickness is less than λ/24. The method could be particularly useful for the design of FSSs at lower frequencies with longer wavelengths. Thus, a novel approach for designing extreme low profile high-order bandpass frequency selective surfaces is introduced in this chapter. The structure is built in such way to obtain bandpass response by the coupling between the third harmonic responses of the resonators instead of the fundamentals. By parametric study of the proposed structure, one can make the coupling between the third harmonics weak with a thinner substrate, and then a flat in-band response can be achieved. The overall thickness can be reduced to λ/75. Chapter 7 demonstrates FSSs with sharp transition edges and almost flat bandpass for submillimetre wave and terahertz applications. The proposed structure exhibits a low insertion loss in the desired band. The structure is realised by combining bandstop and bandpass FSS structures on the same plane. By cascading more than one layer of surfaces, separated by dielectric slabs, the response with the desired flat passband characteristics can be achieved. The structure is polarisation independent and exhibits low insertion loss at the passband around 170 GHz. Finally, Chapter 8 demonstrates an extremely small-size high impedance surface (HIS) array element. A trade-off between a miniaturised element size and a lowered thickness of the grounded substrate is made to design an extremely low profile HIS. Additionally, we propose a way to modify existing classical RFID tag designs to enable them to operate well when they are attached to dielectric materials. Compared with using an HIS, the antenna bandwidth after being loaded with the proposed FSS is increased by approximately 100%.
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Orr, Robert Mervyn. "Application of frequency selective surfaces in circular polarization antenna technologies." Thesis, Queen's University Belfast, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.675421.
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The objective of the work in this thesis is to design lightweight, low profile, circular polarization (CP) antenna technologies which have potential for use in satellite communication systems. A new class of CP Fabry-Perot (FP) cavity antenna which may be used as a replacement for bulky CP horn antennas is developed. A double-sided partially reflective surface (PRS) is employed in the design. The resulting class of antennas are appealing as they allow a specified gain in CP to be achieved while maintaining the simplicity of a single cavity structure and a linearly polarized (LP) primary feed. An example demonstrator antenna with a gain of approximately 21 dB at 15 GHz is designed using the full-wave electromagnetic simulation tool, CST Microwave Studio (MWS). A prototype is produced and measured in order to validate the simulation results. Frequency selective surfaces (FSS) are employed as quasi-optical diplexers in satellite communication systems to facilitate multiband reflector antenna operation therefore allowing multiple feed antennas to share the same aperture. In this thesis quasi-optical diplexers suitable for CP dual frequency band operation are considered. A new class of polarizing surface is developed which in a given frequency band reflects incident linearly polarized waves with circular polarization (CP) while at other frequencies it is transparent allowing incident waves to be transmitted. In addition, a new type of CP FSS which conserves a CP signal upon reflection and transmission is designed. The axial ratio in the reflection and transmission bands is reported for both structures. Numerical EM simulation supported as necessary with analytical analysis is used throughout.
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Kiani, Ghaffer I. (Ghaffer Iqbal). "Passive, active and absorbing frequency selective surfaces for wireless communication applications." Australia : Macquarie University, 2008. http://hdl.handle.net/1959.14/76611.
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"March, 2009".Thesis (PhD)--Macquarie University, Faculty of Science, Dept. of Physics & Engineering, 2008.
Bibliography: p. 145-158.
Introduction -- Frequency selective surfaces -- Absorb/transmit frequency selective surface absorber -- Switchable frequency selective surface for wireless applications -- Energy-saving glass characterisation -- Frequency selective surface solution for energy-saving glass -- Conclusion.
This thesis presents three topics related to frequency selective surfaces (FSSs), namely bsorb/transmit FSSs, active FSSs and passive bandpass FSSs for energy-saving glass used in modern buildings. These three FSSs are unique in their design and functionalities. The absorb/transmit FSS is a novel dual-layer frequency selective surface for 5 GHz WLAN applications. This FSS can stop propagation of specific bands by absorbing as opposed to re ecting, while passing other useful signals. This is in contrast to the conventional Salisbury and Jaumann absorbers, which provide good absorption in the desired band while the out-of-band frequencies are attenuated. The second topic is a single-layer bandpass active FSS that can be switched between ON and OFF states to control the transmission in 2.45 GHz WLAN applications. Previously, researchers have focused on the bandstop and dual-layer versions of the active FSS. This is in contrast to the design presented in this thesis which is single-layer and provides extra advantage in a practical WLAN environment. Also the dc biasing techniques that were used for the active FSS design are easier to implement and provide good frequency stability for different angles of incidence and polarisations in both ON and OFF states. The last topic is on the use of a bandpass FSS in energy-saving glass panels used in building design. The manufacturers of these glass panels apply a very thin metal-oxide coating on one side of the glass panels to provide extra infrared (heat) attenuation. However, due to the presence of the coating, these energy-saving glass panels also attenuate communication signals such as GSM 900, GSM 1800/1900, UMTS and 3G mobile signals etc. This creates a major communication problem when buildings are constructed with windows of this glass. In this thesis, a solution to this problem is presented by designing and etching a cross-dipole bandpass FSS on the coated side of the glass to pass the useful signals while keeping infrared attenuation at an acceptable level. One of the advantages of this FSS design is that measured material values of the metal-oxide coating are used for simulations, which have not been done previously.
Mode of access: World Wide Web.
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Loui, Hung. "Modal analysis and design of compound gratings and frequency selective surfaces." Diss., Connect to online resource, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3219048.
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Pryor, Jonothan B. "Oh ohmic losses in frequency selective surfaces at near-infrared wavelengths." The Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=osu1068663394.
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Pryor, Jonothan B. "On ohmic losses in frequency selective surfaces at near-infrared wavelengths." Columbus, Ohio : Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1068663394.
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Thesis (Ph. D.)--Ohio State University, 2003.Title from first page of PDF file. Document formatted into pages; contains xxiii, 152 p.; also includes graphics (some col.). Includes abstract and vita. Advisor: Benedikt Munk, Dept. of Electrical Engineering. Includes bibliographical references (p. 250-252).
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Kiani, Ghaffer I. "Passive, active and absorbing frequency selective surfaces for wireless communication applications." Phd thesis, Australia : Macquarie University, 2008. http://hdl.handle.net/1959.14/76611.
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Irci, Erdinc. "Low-Profile Wideband Antennas Based on Tightly Coupled Dipole and Patch Elements." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1316456337.
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Kipp, Robert. "Mixed potential integral equation solutions for layered media structures : high frequency interconnects and frequency selective surfaces /." Thesis, Connect to this title online; UW restricted, 1993. http://hdl.handle.net/1773/5974.
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KOLECK, THIERRY. "Modelisation de surfaces selectives en frequence de dimensions finies." Paris 11, 1998. http://www.theses.fr/1998PA112120.
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Une surface selective en frequence (ssf) est constituee d'un ecran metallique periodique et d'une structure dielectrique multicouche. Son caractere selectif non seulement en frequence, mais aussi en incidence ou en polarisation a permis de trouver un grand nombre d'application (reflecteur dichroique, radomes, polariseur) de nombreux travaux sur la modelisation de ssf ont considere la surface comme infinie. L'application du theoreme de floquet permet alors une simplification du probleme. Cette these presente des travaux permettant de prendre en compte l'aspect fini de la ssf. Dans un premier temps, l'etude se limite au cas plan. La premiere approche, basee sur la methode de galerkin spectrale permet d'aborder le probleme de maniere exacte. Tous les couplages entre motifs sont calcules. La periodicite de la ssf implique que le systeme matriciel resultant de la methode de moments est une matrice de toeplitz par blocs a 2 niveaux. L'exploitation de cette propriete de la matrice permet de reduire considerablement l'espace memoire necessaire. Cependant, les limitations sur les dimensions de la ssf sont rapidement atteinte. La deuxieme approche presentee permet de s'affranchir des limites sur la dimension de la ssf etudiee. L'approximation de la surface finie par une surface infinie eclairee localement est utilisee. La synthese de l'illumination locale est realisee par un spectre d'ondes planes. L'eclairement par une source quelconque est aussi traite. Le probleme de la courbure de la ssf finie est ensuite abordee. Le probleme est alors exprime dans un systeme de coordonnees cylindriques. La resolution fait appel a la methode de galerkin spectrale.
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Mateo, Segura Carolina. "Near-field analysis of frequency selective surfaces and application in directive antennas." Thesis, Heriot-Watt University, 2010. http://hdl.handle.net/10399/2397.
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A near-field characterisation of two dimensional metallo-dielectric frequency selective surfaces either in a single or double layer configuration is presented in this thesis. Motivated by the current attention of the electromagnetic properties of near-fields, an in-house periodic MoM-based computational tool is developed for the efficient and rigorous estimation of the near-fields in frequency selective surfaces (FSS) illuminated by a plane wave. For this purpose a thorough convergence study related to the calculation of the near fields is initially presented. The near-field estimation allows us to calculate the power stored in an FSS at resonance which, in turn, can be used in the calculation of the loaded quality factor of the FSS. Based on the characterisation of various topologies, new techniques for the analysis of highly-directive and broadband leaky wave antennas are proposed. An initial design based on a perturbed FSS results in a structure with multiband response and near-fields enhanced by more than 70 fold, which can be relevant to sensor applications. Subsequently, the near-field technique is used in combination with reciprocity for the extraction of the radiation patterns in Fabry-Perot cavity antennas formed between a FSS and a metamaterial ground plane. In combination with traditional array theory the complex dispersion characteristics of high-gain sub-wavelength 2-D Fabry-Perot leaky-wave antennas (LWA) consisting of two periodic metallodielectric arrays over a ground plane are extracted. This yields a fast and rigorous tool for the characterisation of this type of antennas. Design guidelines are given throughout to synthesize a highly-directive antenna and a broadband leakywave antenna. This thesis was fully funded by the Joint Research Institute for Integrated Systems in Edinburgh, Scotland.
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Stylianou, Andreas. "Iterative computation of scattering from finite and multi-layer frequency selective surfaces." Thesis, Loughborough University, 1992. https://dspace.lboro.ac.uk/2134/25625.
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Analysing Frequency Selective Surfaces (FSS) often requires solving integral equations that may have asymmetric and singularity behaved kernels. These singularities together with the array geometry can introduce significant complexities to the solution of the problem. The thesis deals with the solution of such equations using a spectral iterative method. The analysis is based on minimising an error criterion, which is defined as the difference between the scattered and impressed waves. Computer models have been developed as a means of predicting the radiation performance of single and multiple layer FSS. The research involves two separate but related studies. The first study is concerned with finite arrays of conducting elements. The effect of the dielectric substrate and size of the arrays to the scattered field is examined. In the second study the iterative scheme is modified accordingly in order to solve a set of integral equations for a multilayer array where each layer is assumed to be of infinite extent. The analysis takes into account the interlayer coupling and the dielectric substrates/superstrates adjacent to the array elements. The results obtained from both studies are compared with the method of moments solution as well as with experimental results.
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Davenport, Christopher James. "Periodic frequency selective surfaces for reduction of specular scatter in indoor applications." Thesis, University of Sheffield, 2015. http://etheses.whiterose.ac.uk/9606/.
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This thesis investigates the use of a variety of passive frequency selective surfaces for specular scatter reduction. Motivation from this work stems from the increased interest in controlling propagation in indoor environments. Influencing the propagation environment using both passive and active structures is of current research interest due to the increased use of wireless devices inside building structures. This thesis aims to develop surfaces suitable for installation on corridor walls to work alongside existing solutions. An initial literature review of frequency selective surfaces; particularly for use inside buildings to create smart environments, suggests reducing the propagation down corridors could be beneficial in decreasing co-channel interference although no solutions have been offered. Development of the initial comb frequency selective surface (CR-FSS) enabled measurement systems and simulation models to be constructed and compared. Due to the various limitations of the CR-FSS, design modifications and evolutions are investigated to overcome issues with poor angular performance, polarisation dependant performance, and experimental manufacture. The initial challenge was to create a rotationally symmetrical surface which could reduce specular scatter from additional angles of incidence in the elevation plane. A pin reflection FSS (PR-FSS) was created, however investigation of the structure showed that it was ineffectual for TE polarisation. In a multipath environment this could be an issue which effects performance. Investigation of additional variations of the CR-FSS such as the slanted comb FSS (SC-FSS) and crenelated CR-FSS complete the analysis. A validation of a frequency selective comb structures is conducted with in-building multipath simulations. Statistical plots show that a comb structure can be used to significantly improve the signal-to-interference ratio (SIR) of co-channel transmitters at 2.4 GHz by reducing propagation down a corridor.