Dissertations / Theses on the topic 'Multimode Antenna'

International Telemetering Conference Proceedings / October 26-29, 1992 / Town and Country Hotel and Convention Center, San Diego, California<br>The GPS Satellite System provides precise determination of time, space, and position of aerospace (airborne) vehicles during flight and flight test situations. The cost of "GPS" equipment has been decreasing dramatically -- a phenomenon similar to that which was experienced with "hand held" calculators 20 years or so ago. By the use of a multigain (and beam) antenna and GPS, a very low cost single axis system can be utilized for reception of telemetry and at the same time to provide accurate position, velocity, and acceleration information concerning the airborne vehicle.

This thesis describes original work on the broadband and multiband matching of microstrip patch antennas. Microstrip patch antennas suffer from many constraints on their performance. One major restriction is their narrow impedance bandwidth. An effective method to resolve this is adding more resonators to the antenna structure to achieve multi-resonance and hence wider bandwidth. Structures such as circular, square and triangular patch antennas may support two orthogonal resonant modes or polarisations. This allows excitation of an additional resonance beside the fundamental. With the correct coupling between the resonant modes, the impedance bandwidth can be significantly increased. The equivalent circuit of such structures is similar to those used in microwave filter design. Using techniques normally employed in filter synthesis, the equivalent circuits can be generated, and aid in finding the couplings and dimensions of the specified antenna requirement. The bandwidth of circular microstrip patch antennas is significantly increased by exciting two modes on a single circular microstrip antenna, and four modes using two stacked circular microstrip patches. In this work, the designs are also extended into multimode antennas achieving multi-frequency operation.

Les réseaux réflecteurs sont une alternative prometteuse aux antennes à réflecteurs pour la réalisation de diagrammes de rayonnement directifs ou de couvertures formées, notamment dans le spatial ou dans l'aéronautique. Constitués d'un grand nombre de cellules unitaires dont il faut optimiser la géométrie individuellement, ils restent toutefois difficiles à concevoir. Cette thèse traite de la synthèse des antennes réseau à réflecteur. Aujourd'hui les méthodes utilisées pour les concevoir exploitent, pour la majorité, les logiciels de simulation électromagnétique. Elles sont très coûteuses en temps de calcul et requièrent au final des hypothèses simplificatrices. L'objectif de cette thèse est de répondre à la question suivante : est-il possible de synthétiser de manière purement·analytique un réseau réflecteur? Nous avons répondu à cette question en exploitant la méthode de modélisation multimodale. Elle consiste à représenter la cellule unitaire sous la forme d'un circuit équivalent. Ses propriétés remarquables permettent de prédire analytiquement la phase en réflexion en fonction des dimensions de la cellule unitaire. Un réflecteur composé de cellules unitaires à motif 1 D de;type ruban métallique a tout d'abord été étudié et évalué dans le cadre de la synthèse analytique d'une structure simple. Cette étude a permis de valider la méthode de modélisation en vue de son utilisation dans la synthèse analytique de réseaux réflecteurs. Trois réseaux réflecteurs composés de cellules unitaires 2D de types patch et grille ont ensuite·été synthétisés sur la base de trois spécifications différentes, ceci afin de tester la synthèse analytique dans des configurations de plus en plus contraignantes. Finalement il s'est révélé que la méthode de modélisation multimodale et prometteuse mais que sa précision doit encore être améliorée pour permettre une synthèse complète de réseau réflecteur<br>Reflectarrays antennas are a promising alternative to reflector antennas in order to produce focused and contoured beams especially for aeronautics and space applications. A reflectarray antenna is made up of ah array of unit cell that provide a pre-adjusted phasing to form the desired beam.The synthesis of a reflectarray consists in fixing the geometrical dimensions of each unit cell to generate the desired phase law. This thesis focuses on the synthesis of reflectarray. The current methods are mostly based on full­wave analysis and so they are time consuming.The purpose of this thesis is to answer at the following question: a reflectarray can be fully analytically synthesized? We answer it by using the multimodal method. The unit cell is then represented by an equivalent circuit. Using its remarkable properties, the reflected phase can be analytically predicted according to the geometrical dimensions of the unit cell. We used it firstly to synthesize a reflector where the unit cell is composed or a metallic strip. This study has validated this method in order to synthesize reflectarray, Then three reflectarrays have been synthesized based on three specifications. Finally, the multimodal method is promising but the precision has to be improving in order to fully synthesize a reflectarray

ITC/USA 2008 Conference Proceedings / The Forty-Fourth Annual International Telemetering Conference and Technical Exhibition / October 27-30, 2008 / Town and Country Resort & Convention Center, San Diego, California<br>Enclosed weapon bays on modern aircraft interfere with prelaunch, Flight Termination System verification during training test launches. Range safety personnel need to verify the functionality of the flight termination system prior to missile launch. The missile telemetry RF is highly attenuated when the aircraft missile bay doors are closed, limiting the range for which the aircraft can fly during training flights. Teletronics Technology Corporation and Lockheed Martin designed a system to provide telemetry data for these aircraft. The system re-radiates the telemetry from the missiles with the weapon bay doors closed. This paper describes the design considerations for this flexible system that accommodates multiple weapon systems in multiple weapon bay configurations.

Thesis (PhD) -- Stellenbosch University, 2001.<br>Some digitised pages may appear illegible due to the condition of the original hard copy.<br>ENGLISH ABSTRACT: A new technique for the design of multimode devices in overmoded waveguide is presented. The technique applies the principle of growth-based design and uses a conceptual functional block representation of the design structure to provide necessary flexibility to the design algorithms. Two growth based design strategies are proposed and evaluated. The first uses a generalized synthesis-oriented scanning technique, and the second uses an evolutionary strategy. The techniques provide reliable solutions to a variety of multimode design problems. In order to facilitate sufficiently fast numerical analysis, novel enhancements of the mode matching technique are developed and the use of surrogate models is investigated. In addition, to allow physical evaluation of the finished devices, original techniques of measuring multimode devices are formulated and utilised. Two practical problems are used to evaluate the performance of the design procedures. The first is the design of overmoded waveguide chokes for microwave heating facilities, and the second is the design of multimode horns for antenna and spatial power combining applications. Various examples of each type of problem are presented with measurements of manufactured solutions.<br>AFRIKAANSE OPSOMMING: ’n Nuwe tegniek vir die ontwerp van multimodusstelsels binne multimodus golfleier word voorgestel. Die tegniek maak gebruik van die beginsel van groei-georienteerde ontwerp en ontgin ’n konsepsuele funksionele module-voorstelling van die ontwerpstruktuur om die nodige buigsaamheid aan die ontwerpsalgoritmes te verleen. Twee groei-georienteerde ontwerpstrategiee word aangebied en geevalueer. Die eerste is gebasseer op ’n veralgemeende sintese-georienteerde skandeertegniek, en die tweede maak gebruik van ’n evolusie-strategie. Die tegniek verskaf betroubare oplossings vir ’n verskeidenheid van multimodusontwerpsprobleme. Ten einde ’n numeriese analise-tegniek daar te stel wat vinnig genoeg is, word oorspronklike verbeterings van die modal-pas metode ontwikkel en surrogaatmodelle is ook ondersoek. Verder, vir fisiese evaluasie, word oorspronklike meettegnieke vir multimodusstelsels geformuleer en gebruik. Twee praktiese probleme word gebruik om die ontwerpprosedures te evalueer. Die eerste is die ontwerp van multimodus golfleierdrywingsdempers vir mikrogolfverhitting, en die tweede is die ontwerp van multimodus horings vir antenna- en ruimtelike drywingskombineerdertoepasings. Verskeie voorbeelde van elke tipe probleem word gegee met metings van gei'mplementeerde oplossings.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010.<br>ENGLISH ABSTRACT: The aggressive space mapping algorithm is used in this project for the optimisation of electromagnetic structures. This technique combines the use of fast, less accurate models with more time-consuming, high precision models in the optimisation of a design. MATLAB’s technical computing environment possesses powerful tools for optimisation as well as the graphical representation and mathematical post-processing of data. A software interface, which uses Visual Basic for Applications, is created between MATLAB and the electromagnetic solvers, CST Microwave Studio and μWave Wizard, that are used for the fine and coarse model calculations. The interface enables the direct interchange of data, which allows MATLAB to control the optimisation for the automation of the design process. The optimisation of a microwave coaxial resonator with input coupling is used to demonstrate the design environment. An accurate equivalent circuit model is available to describe the problem. The space mapping optimisation of this structure works well, with a significant improvement in the efficiency of the optimisation when compared to standard optimisation techniques. Multimode horn antennas are of interest for use as feeds in radio-astronomy telescope systems. The design of a stepped circular horn antenna in the space mapping design environment is presented. The horn’s radiation pattern is optimised for low cross-polarisation. This structure is much more complex to model than the resonator example. The generalised scattering matrix representation is used in the coarse model description. The far-fields are calculated from the aperture fields by means of the Fast Fourier Transform. Various tests confirm that the optimisation is steered in the right direction as long as the coarse model response follows the trend of the fine model response over the optimisation space. The presented design environment is a powerful tool for the automation of the design of electromagnetic structures.<br>AFRIKAANSE OPSOMMING: Die aggressiewe ruimte-afbeelding algoritme word in hierdie projek gebruik vir die optimering van elektromagnetiese strukture. Hierdie tegniek kombineer die gebruik van vinnige, minder akkurate modelle tesame met tydrowende hoë presisie modelle tydens die optimering van ’n ontwerp. MATLAB se tegniese verwerkingsomgewing beskik oor kragtige gereedskap vir optimering sowel as die grafiese voorstelling en wiskundige verwerking van data. ’n Sagteware koppelvlak, wat Visual Basic for Applications benut, word geskep tussen MATLAB en die elektromagnetiese oplossers, CST Microwave Studio en μWave Wizard, wat vir die fyn en growwe model berekeninge gebruik word. Hierdie koppelvlak maak die direkte uitruiling van data moontlik, wat MATLAB in staat stel om die optimering te beheer ten einde die ontwerpsproses te outomatiseer. Die optimering van ’n mikrogolf koaksiale resoneerder met intree koppeling word gebruik om die ontwerpsomgewing te demonstreer. ’n Akkurate ekwivalente stroombaanmodel is beskikbaar om die probleem mee te beskryf. Die ruimte-afbeelding optimering van hierdie struktuur werk goed en toon ’n aansienlike verbetering in die doeltreffendheid van die optimering wanneer dit met standaard optimeringstegnieke vergelyk word. Multimodus horingantennes is van belang in radio-astronomie, waar dit as voere vir teleskope gebruik word. Die ontwerp van ’n trapvormige, sirkelvormige horingantenne in die ruimte-afbeelding ontwerpsomgewing word aangebied. Die stralingspatroon van die horing word optimeer vir lae kruispolarisasie. Hierdie struktuur is heelwat meer ingewikkeld om te modelleer as die resoneerder voorbeeld. Die veralgemeende strooimatriks voorstelling word gebruik in die growwe model beskrywing. Die ver-velde word bereken vanaf die velde in die bek van die antenne, deur gebruik te maak van die Vinnige Fourier Transform. Verskeie toetse bevestig dat die optimering in die regte rigting gestuur word, solank as wat die growwe model se gedrag dié van die fyn model oor die optimeringsgebied navolg. Die ontwerpsomgewing wat hier aangebied word, is ’n kragtige stuk gereedskap vir die outomatisering van die ontwerp van elektromagnetiese strukture.

CAPES<br>Neste trabalho são apresentados os resultados experimentais para medidas simultâneas de índice de refração e da temperatura, com a utilização de uma rede de Bragg gravada em fibra multimodo corroída (EMFBGs). Foram trabalhados com os três modos de propagação restantes após a corrosão da fibra, utilizando as variações dos comprimentos de onda de Bragg destes modos para encontrar o índice de refração e/ou a temperatura. Durante os procedimentos experimentais foram observadas as influências que a variação do índice de refração tem sobre a sensibilidade térmica, bem como as que a variação de temperatura causa na sensibilidade da rede ao índice de refração. A resposta do dispositivo as variações desses parâmetros foram aproximadas por superfícies planas e as sensibilidades cruzadas foram utilizadas para corrigir a aproximação. Os resultados mostram que é possível determinar os valores de índice de refração em uma faixa de 1,33 até 1,46 com um erro da ordem de 10-3.<br>In this work the experimental results are presented applying simultaneous refractive index and temperature measures, with an Etched Multimode Fiber Bragg Grating (EMFBGs). After the fiber corrosion, the three remaining propagation modes were used to the work, utilizing variations of the Bragg wavelengths of those modes to find the refractive index and/or temperature. During the experimental procedures the influences of the refractive index variation has on the thermal sensitivity were observed, as well as what the temperature variation causes in the sensitivity of the network to the index of refraction. The device response to the variations of those parameters were approximated by flat surfaces and the cross-sensitivities were used to correct the approximation. The results show that it is possible to determine the refractive index values in a range of 1.33 to 1.45 with an error of the order of 10-3.

CAPES<br>Neste trabalho são apresentados os resultados numéricos e experimentais de refratômetros baseados em redes de Bragg produzidos em fibras óticas multimodo. O desempenho dessas redes é comparado com o desempenho de redes tradicionais gravadas em fibras óticas monomodo. Para que as redes apresentem sensibilidade ao índice de refração elas são submetidas à corrosão química e após esse processo a fibra ótica monomodo apresentou um diâmetro de (18,08 ± 0,01) m, enquanto que a fibra ótica multimodo apresentou um diâmetro de (17,10 ± 0,10) m. Os resultados deste estudo mostraram que as redes de Bragg gravadas em fibras óticas multimodo apresentaram maior sensibilidade ao índice de refração externo, bem como maior faixa dinâmica, em relação às redes gravadas em fibras óticas monomodo. Determinou-se experimentalmente uma sensibilidade de 41,9 nm/UIR para a rede gravada em fibra multimodo, contra uma sensibilidade de 1,3 nm/UIR para a rede gravada em fibra monomodo, sendo que tais sensibilidades foram obtidas para um índice de refração de 1,4656. O uso de fibras óticas multimodo conferiu maior sensibilidade ao sistema, além de ter proporcionado aumento da robustez mecânica em função dos maiores diâmetros empregados, quando comparados às fibras óticas monomodo com sensibilidade similares. Os dispositivos estudados foram aplicados na determinação da concentração de óleo vegetal na mistura óleo-biodiesel, que é um dos parâmetros de qualidade do processo de produção e distribuição do combustível. Os resultados obtidos mostram que utilizando o modo 1 é possível obter uma resolução de 2,11% v/v quando a concentração de óleo se aproxima de 0,00% e 0,28% v/v para 70% v/v de concentração de óleo. Caso a análise seja realizada utilizando o modo 2 a resolução obtida é de 1,37% v/v quando a concentração de óleo se aproxima de 0,00% e 0,13% v/v para 60,51% v/v de concentração de óleo.<br>In this work are reported the experimental and numerical results of a refractometer based on fiber Bragg gratings produced on multimode optical fibers. The performance of the gratings inscribed in multimode optical fibers is compared with the gratings inscribed in single mode optical fibers. In order to become sensitive to the external refractive index, the gratings were subdued to a chemical etching process, after which the single mode fiber presented a (18.08 ± 0.01) m diameter while the multimode fiber presented a (17.10 ± 0.10) m diameter. The results of this study showed that the gratings inscribed in multimode optical fibers presented a higher sensitivity to the external refractive index, and a broader dynamic range as well, when compared with the gratings inscribed in single mode optical fibers. Experimental results showed a 41.9 nm/RIU sensitivity for gratings inscribed in multimode optical fibers and a 1.3 nm/RIU sensitivity for gratings inscribed in single mode optical fibers, being both fibers exposed to a 1.4656 external refractive index. Multimode optical fibers provided an increase in the system sensitivity, and a mechanical robustness improvement as well, due to the higher optical fibers diameters employed when compared with single mode optical fibers with similar sensitivities. The devices were used to determine the vegetal oil concentration of oil-biodiesel blends, which stands as a quality parameter for the fuel production and distribution. The results showed that the mode 1 allowed a resolution of 2.11% v/v for 0.00 % of oil concentration and 0.28 % v/v when oil concentration was 70.00% v/v. Analysis performed with mode 2 showed a resolution of 1.37% v/v for 0.00 % of oil concentration and 0.13 % v/v when oil concentration was 60.51% v/v.

碩士<br>義守大學<br>電子工程學系<br>106<br>When the smartphone uses glass casing, the modern technology needs a combination of metal-rimmed and a glass casing. If the metal-rimmed can be part of the antenna, how to design and fabricate it will be an important issue for the antenna designer. 　　This paper proposes multimode antenna for metal-rimmed smartphone applications. Without metal-rimmed the size is 60*110 mm2 and the ground clearance is 40*5 mm2 .The size is 64*114*5 mm3 when the metal-rimmed is included. The operating frequency includes the LTE 900, 1800, 2100, 2600 MHz, and Wi-Fi 2400 MHz. 　　This paper is divided into three major parts: the first is an inverted L-shaped antenna, the rectangular and the C-type ground plane to cooperate with each other, which is with the advantage of not only generating the frequency, but also reducing the clearance area. The second is using three patches to create a coupling loop that excites the desired frequency. The third is to implement a metal rimmed antenna.

碩士<br>國立臺北科技大學<br>電腦與通訊研究所<br>97<br>A novel broadband antenna miniaturization is presented in this thesis. The antenna is proposed for operating at whole world DTV reception band (470 MHz ~ 860 MHz). This antenna used the 50 Ω microstip line to feed, In microstip line’s ground plane slotting let microstip line return current path increase to radiation effect. To achieve broadband structure, the proposed antenna is composed of seven resonances path in the ground plane. To achieve compact structure, the proposed antenna is use signal line and ground plane coupling induce the capacitance effect. The impedance matching and bandwidth for the presented antenna are mainly affected by sheet metal on signal line. The antenna can get omnidirectional radiation pattern in the whole frequency band. The measurement result is agree with simulation. In order to enhance receiver receiving performance for this antenna in DTV signal receptions, the LNA is used to increase the receiving signal power intensity. Finally, the LNA be fabricated and integrated in the ground plane to prove the receiver signal power intensity by practical measurement. The designed antenna with overall size of only 20 × 20 × 0.8 mm3, and combined the LNA overall size of only 20 × 30 × 0.8 mm3.

碩士<br>國立交通大學<br>電控工程研究所<br>98<br>In this thesis, we proposed reduced-complexity algorithms to select appropriate transmit antennas for MIMO system with zero-forcing receiver. Two criteria for selecting antennas are derived: achievable data rate maximization and average symbol error rate minimization. In addition, bit allocation is also applied to improve the performance. The computational complexity can be reduced by simplifying search strategy and matrix inversion. The computational complexity analysis and simulation results are given to see that the advantages of the proposed algorithm.