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Rahman, Md Khalilur, and Chuanhui Xia. "Antenna diversity with opportunistic combining." Thesis, Linköpings universitet, Fysik och elektroteknik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-91332.
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In modern telecommunication technologies, the requirement for signal reliability is higher and higher but fading is the main challenge for signal reliability. Different types of techniques have been studied to mitigate this fading but MIMO (Multiple Input Multiple Output) has been studied extensively in wireless communication systems to overcome small-scale fading, which is an efficient way to improve signal-to-noise and bit error rates. In this thesis, all works were operated at 2.45 GHz. Planar-Inverted F antenna (PIFA) is used for mobile phone due to its low profile and high gain. In this thesis, two PIFAs are used for antenna diversity. All the simulation of the antennas was performed in High Frequency Structure Simulator (HFSS). Advanced Design system (ADS) is used for Wilkinson combiner design and simulation and overall layout design for PCB fabrication. Phase shifters are used to change the phase of each input signals. All measurements have been done in both reverberation chamber and office environment and the two results are different. Office environment measurements have been done in PCB lab at Linköping University and reverberation measurements have been done at SP Technical Research Institute of Sweden. Finally a conclusion was drawn about the performance of this thesis.
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Brown, Timothy W. C. "Antenna diversity for mobile terminals." Thesis, University of Surrey, 2002. http://epubs.surrey.ac.uk/2125/.
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Bui, Do Hanh Ngan. "Antennes souples imprimables pour la récupération de champs électromagnétiques ambiants." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAT062/document.
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L’Internet-of-Things désigne un développement en plein essor d’objets interconnectés et qui sont susceptibles de modifier nombre de services au sein de l’industrie comme pour la personne. Les développements actuels buttent sur plusieurs verrous dont celui de l’autonomie énergétique des objets ou encore des procédés de fabrication économiquement acceptables et respectueux de la planète. Dans ce contexte, la récupération d'énergie est une thématique largement répandue faisant appel à des sources très variées (mécanique, thermique, électromagnétique...). Cette thèse est notamment orientée vers la récupération d'énergie électromagnétique ambiante. Le second point caractéristique de cette thèse est de s'intéresser à des substrats souples et si possible recyclables. Le défi consiste à récupérer l’énergie provenant d’un champ électromagnétique ambiant extrêmement faible : ceci concerne l’antenne, qui doit par ailleurs répondre à une exigence de flexibilité pour son intégration future à un objet souple et déformable, et l’électronique de traitement de l’énergie.Le travail de thèse est articulé autour de trois phases principales :Dans la première phase, il s’agissait de l’étude des structures d’antennes compatibles en fréquence et en puissance reçue avec l’application de récupération d’énergie et une réalisation physique sur base souple (papier, tissu...). Cette phase a permis de présenter les différentes approches pour combiner les sources RF.Dans la deuxième phase, il s’agit de l’étude sur le rôle de circuits redresseurs dans le système de récupérer d’énergie. Les méthodes d'extraction des paramètres sont discutées en dissociant chaque élément et leurs rôles. De nombreuses mesures ont été réalisées afin de comparer différents modèles de la diode utilisée pour le redressement, en tenant compte également de l'impact réel du processus de fabrication et du processus de mesure.Une troisième phase permet l’optimisation de l’ensemble antenne et électronique (rectenna) pour divers scenarii et le suivi de la variabilité pour maintenir les pertes du système a minima. La réalisation de démonstrateurs pertinents, testés et caractérisés est présentéeInternet-of-Things means a growing development of interconnected objects that are likely to change many services within the industry as well as for the individual. Several barriers, including the energy autonomy of objects or production processes that are economically acceptable and respectful of the planet, hamper current developments. In this context, energy recovery is a widespread theme using a wide range of sources (mechanical, thermal, electromagnetic, etc.). This thesis is oriented towards the recovery of ambient electromagnetic energy. The second characteristic point of this thesis is to focus on flexible and, if possible, recyclable substrates. The challenge is to recover energy from an extremely low ambient electromagnetic field: this concerns the antenna, which must also meet a requirement for flexibility for its future integration with a flexible and deformable object, and the electronics of energy processing.The work of this thesis conducted in three phases.In the first phase, it was the study of the antenna structures compatible with frequency and power received with the energy harvesting application and a physical realization on flexible base (paper, textile, etc.). This phase allowed presenting the different approaches to combining the RF sources.In the second phase, the study on the role of rectifying circuit in the system of recovering wireless energy was presented. Methods for extracting parameters were discussed by separating each element and its roles. Numerous measurements have been conducted to compare different models of the diode, taking into account also the actual impact of the manufacturing process and the measurement process.A third phase allows the optimization of the antenna and electronic assembly (rectenna) for various scenarios and the monitoring of variability to keep the losses of the system at minima. The production of relevant demonstrators, test and characterization were presented
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Zhang, Shuai. "Investigating and Enhancing Performance of Multiple Antenna Systems in Compact MIMO/Diversity Terminals." Doctoral thesis, KTH, Elektroteknisk teori och konstruktion, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-116402.
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Today, owners of small communicating device are interested in transmitting or receiving various multimedia data. By increasing the number of antennas at the transmitter and/or the receiver side of the wireless link, the diversity/Multiple-Input Multiple-Output (MIMO) techniques can increase wireless channel capacity without the need for additional power or spectrum in rich scattering environments. However, due to the limited space of small mobile devices, the correlation coefficients between MIMO antenna elements are very high and the total efficiencies of MIMO elements degrade severely. Furthermore, the human body causes high losses on electromagnetic wave. During the applications, the presence of users may result in the significant reduction of the antenna total efficiencies and highly affects the correlations of MIMO antenna systems. The aims of this thesis are to investigate and enhance the MIMO/diversity performance of multiple antenna systems in the free space and the presence of users. The background and theory of multiple antenna systems are introduced briefly first. Several figures of merits are provided and discussed to evaluate the multiple antenna systems. The decoupling techniques are investigated in the multiple antenna systems operating at the higher frequencies (above 1.7 GHz) and with high radiation efficiency. The single, dual and wide band isolation enhancements are realized through the half-wavelength decoupling slot, quarter-wavelength decoupling slot with T-shaped impedance transformer, tree-like parasitic element with multiple resonances, as well as the different polarizations and radiation patterns of multiple antennas. In the lower bands (lower than 960 MHz), due to the low radiation efficiency and strong chassis mode, the work mainly focused on how to directly reduce the correlations and enlarge the total efficiency. A new mode of mutual scattering mode is introduced. By increasing the Q factors, the radiation patterns of multiple antennas are separated automatically to reduce the correlations. With the inter-element distance larger than a certain distance, a higher Q factor also improved the total efficiency apart from the low correlation. A wideband LTE MIMO antenna with multiple resonances is proposed in mobile terminals. The high Q factors required for the low correlation and high efficiencies in mutual scattering mode is reduced with another mode of diagonal antenna-chassis mode. Hence, the bandwidth of wideband LTE MIMO antenna with multiple resonances mentioned above can be further enlarged while maintaining the good MIMO/diversity performance. The user effects are studied in different MIMO antenna types, chassis lengths, frequencies, port phases and operating modes. Utilizing these usefully information, an adaptive quad-element MAS has been proposed to reduce the user effects and the some geranial rules not limited to the designed MAS have also been given.QC 20130121
EU Erasmus Mundus External Cooperation Window TANDEM
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Yousaf, Irfan Mehmood. "Optimization of Antenna Pair for Diversity Gain." Thesis, University of Gävle, Department of Technology and Built Environment, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-728.
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In the latest development in the field of telecommunications it has been observed that a lot is expected from the mobile systems. All kinds of communication standards such as Bluetooth, 3G, W-LAN etc. should be present in the same handset. This requires higher data transmission rates and low bit error probability. One of the major problems in achieving this is fading and multi path environment. The other problem is the growing trend of decreasing size of the electronic devices specially handsets. The handsets are getting smaller and thinner. Due to this the antennas in the device come very close to each other which causes high coupling between the antennas resulting in bad diversity gain. Antenna diversity is considered to be one of easier solution to overcome these problems. This thesis presents an implementation of receiver antenna diversity and suggests different optimised networks between the antenna ports for better diversity gain keeping in view the antenna efficiencies. The thesis involves the following steps: simulating the structures, suggesting different networks between the two antenna ports, optimisation and hardware implementation of the networks and finally measurements in reverberation chamber.
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Ager, Lee Patricia. "Cellular base station antenna and diversity study." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0019/MQ48079.pdf.
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Turner, W. C., and R. A. Potter. "UNATTENDED SPACE-DIVERSITY TELEMETRY TRACKING ANTENNA SYSTEM." International Foundation for Telemetering, 1994. http://hdl.handle.net/10150/608826.
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International Telemetering Conference Proceedings / October 17-20, 1994 / Town & Country Hotel and Conference Center, San Diego, CaliforniaA remotely-operated ground telemetry tracking and receiving station is described. The station, operating in a space-diversity mode, is capable of reception and tracking both at VHF and at UHF. The station can be configured and operated from a distance of 240 km using a wide-band land data link. Uplink command at VHF is included as part of the station.
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Anderson, Adam L. "Unitary space-time transmit diversity for multiple antenna self-interference suppression /." Diss., CLICK HERE for online access, 2004. http://contentdm.lib.byu.edu/ETD/image/etd500.pdf.
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Adeane, Jaime. "Spatial diversity in wireless communications : multiple antenna systems and virtual antenna arrays." Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.613069.
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Anreddy, Vikram R. "Indoor MIMO Channels with Polarization Diversity: Measurements and Performance Analysis." Thesis, Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-04112006-093641/.
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Thesis (M. S.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2006.Ingram Mary Ann, Committee Chair ; Durgin, Gregory David, Committee Member ; Williams, Douglas B, Committee Member.
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Leather, Paul Simon Holt. "Antenna diversity for hand-portable radio at 450MHz." Thesis, University of Liverpool, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286174.
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Münster, Matthias. "Antenna diversity-assisted adaptive wireless multiuser OFDM systems." Thesis, University of Southampton, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.273874.
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Narula, Aradhana. "Information theoretic analysis of multiple-antenna transmission diversity." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/10453.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1997.Includes bibliographical references (leaves 125-127).
by Aradhana Narula.
Ph.D.
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Bletsas, Aggelos Anastasiou 1975. "Intelligent antenna sharing in cooperative diversity wireless networks." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/33876.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2005.Includes bibliographical references (p. 143-152).
Cooperative diversity has been recently proposed as a way to form virtual antenna arrays that provide dramatic gains in slow fading wireless environments. However, most of the proposed solutions require simultaneous relay transmissions at the same frequency bands, using distributed space-time coding algorithms. Careful design of distributed space-time coding for the relay channel is usually based on global knowledge of some network parameters or is usually left for future investigation, if there is more than one cooperative relay. We propose a novel scheme that eliminates the need for space-time coding and provides diversity gains on the order of the number of relays in the network. Our scheme first selects the best relay from a set of M available relays and then uses this "best" relay for cooperation between the source and the destination. Information theoretic analysis of outage probability shows that our scheme achieves the same diversity-multiplexing gain tradeoff as achieved by more complex protocols, where coordination and distributed space-time coding for M relay nodes is required. Additionally, the proposed scheme increases the outage and ergodic capacity, compared to non-cooperative communication with increasing number of participating relays, at the low SNR regime and under a total transmission power constraint.
(cont.) Coordination among the participating relays is based on a novel timing protocol that exploits local measurements of the instantaneous channel conditions. The method is distributed and allows for fast selection of the best relay as compared to the channel coherence time. In addition, a methodology to evaluate relay selection performance for any kind of wireless channel statistics is provided. Other methods of network coordination, inspired by natural phenomena of decentralized time synchronization, are analyzed in theory and implemented in practice. It was possible to implement the proposed, virtual antenna formation technique in a custom network of single antenna, half-duplex radios.
by Aggelos Anastasiou Bletsas.
Ph.D.
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Haghdad, Mehdi, and Kamilo Feher. "PSEUDO ERROR DETECTION IN SMART ANTENNA/DIVERSITY SYSTEMS." International Foundation for Telemetering, 2003. http://hdl.handle.net/10150/605363.
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International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, NevadaAn implementation of a Pseudo Error Detection (PSED) system is presented and its performance in conjunction with smart antenna and smart diversity systems tested and evaluated. Non redundancy, instant response and relative simplicity make the Pseudo Error Detectors excellent real time error monitoring systems in smart antenna and smart diversity systems. Because of the Non-redundant Error Detection mechanism in Pseudo Error Detectors, we can monitor the error quality without any coding or overhead. The output of the pseudo error detector in AWGN, selective fading Doppler shift and other interference environments is directly correlated to the BER and BLER. This direct correlation makes it a great tool for online error monitoring of a system and can have numerous applications In a PSED the Eye diagram from the demodulator is sampled once per symbol. By monitoring and comparison of the eye at sampled intervals at different thresholds, we would know if an error has occurred. By integrating this result over a period of time we can get the averaged error level. The results provided in this paper were obtained and verified by both MatLab simulations using dynamic simulation techniques and hardware measurements over dynamic channels.
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Sonkki, M. (Marko). "Wideband and multi-element antennas for mobile applications." Doctoral thesis, Oulun yliopisto, 2013. http://urn.fi/urn:isbn:9789526201085.
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Abstract This dissertation presents wideband and multi-element antennas for mobile applications. It is divided into the following main parts: modal theory, wideband antennas, multi-element antennas, and wideband multi-element antennas. The radiating fields are first studied in terms of spherical scalar and vector modes, and it is shown how these modes correlate with the characteristic current modes on a planar mobile ground plane. The theory part shows how it is possible to excite the same modes on a conventional sphere and a rectangular planar mobile ground plane. The theory refers to the novel wideband antenna structures presented in this dissertation, in terms of current and radiating modes. After studying the modes, the dissertation shows how to excite a radiating antenna mode within a wide frequency bandwidth. To gain this, two main approaches are taken. First, a quasi-complementary antenna (QCA) structure with an electric conductor and magnetic slot is presented, and its characteristics are studied. A QCA UWB antenna, and a QCA element excited with a monopole or a dipole, is presented. The QCA structure compensates for the imaginary part of the input impedance on wide frequency bandwidth, when, at the same time, the fundamental mode is excited to ensure good radiating properties. The second approach uses a symmetrical feeding with two antenna elements to gain a wide frequency bandwidth, the relative -6 dB impedance bandwidth between 37.5–80%. When a field is symmetrically coupled to the conducting ground plane, the excitation avoids the awakening of higher order modes which might disturb the performance of the antenna. It is also shown, by using multiple feeding elements, that the excitation of orthogonal higher order modes on a small radiating ground plane is possible. As the modes are orthogonal to each other, they present a very low correlation. By using this kind of approach, radiation pattern diversity can be obtained in mobile applications within a small volume. On the other hand, when combining two QCA elements to a one multi-element antenna structure, a wideband diversity antenna with an 87.5% relative -6 dB impedance bandwidth, and a wideband MIMO antenna with a 95.0% relative -6 dB impedance bandwidth, are presented with excellent radiation and correlation properties. Also mutual coupling is need to be counted when multi-element antennas are designed. When designing an efficient radiator, it is important to consider an antenna feeding in terms of wideband impedance matching and wideband baluns, not to spoil the antenna performance. The efficient antenna structures and feeding mechanisms are obtained by using commercial 3D electromagnetic simulators to find the desired wideband antenna characteristics. Prototype antennas are measured in most of the presented structures to show their functionality in real. In general, the dissertation presents wideband antenna structures with radiating antenna modes excited on a planar conducting ground plane. The idea is to find structures and feeding mechanisms to excite the fundamental mode, or a certain radiating antenna mode, at a wide frequency bandwidth, by avoiding the excitation of higher order modes which might disturb the antenna performance. It is also shown that, by using multiple feeding elements, it is possible to excite higher order modes on a small antennaTiivistelmä Väitöskirjassa esitetään uusia laajakaistaisia ja monielementtiantenneja matkaviestimiin. Väitöskirja koostuu neljästä pääalueesta: pintavirtojen muototeoria, laajakaistaiset antennit, monielementtiantennit sekä laajakaistaiset monielementtiantennit. Teoriaosassa säteilykenttiä on aluksi tutkittu pallon pinnalla sekä skalaaripotentiaaleina että pintavirtavektoreina, jonka jälkeen niitä on verrattu mobiilin laitteen maatason ominaispintavirtojen synnyttämiin säteilykenttiin. Teoriaosassa osoitetaan, että pallon pinnalla sekä tasomaisella suorakaiteen muotoisella pinnalla on mahdollista herättää samat säteilykentät. Myöhemmin väitöskirjassa esitettävien uudenlaisten antennirakenteiden ominaisuuksia verrataan teoriaosassa esitettyihin pintavirtoihin ja säteilykenttiin. Teoriaosuuden jälkeen osoitetaan miten säteilevä sähkömagneettinen kenttä saadaan herätettyä laajalla taajuusalueella. Tähän on otettu kaksi eri lähestymistapaa, joista ensimmäisessä esitellään ja tutkitaan kvasikomplementaarista antennirakennetta (QCA). Kvasikomplementaarisessa antennirakenteessa sisääntuloimpedanssin imaginaariosa kompensoidaan yhdistämällä sähköinen johde ja magneettinen rako samaan antenniin. Samanaikaisesti perusmuoto herätetään laajalla taajuusalueella, jolla varmistetaan antennin hyvät säteilyominaisuudet koko toimintataajuusalueella. Toisessa lähestymistavassa käytetään kahta symmetrisesti asetettua antennielementtiä, joita syötetään symmetrisesti samalla amplitudilla ja vaiheella. Kun sähkömagneettinen kenttä herätetään symmetrisesti, korkeamman kertaluvun muotojen herättäminen voidaan välttää laajalla taajuusalueella. Symmetrisesti syötetyillä antennirakenteilla saavutettu -6 dB suhteellinen impedanssikaistanleveys on 37.5–80 %. Useita syöttöelementtejä käytettäessä voidaan mobiilin laitteen maatasossa herättää yhdellä pistetaajuudella monta toisistaan riippumatonta säteilykenttää. Koska herätetyt kentät ovat toisistaan riippumattomia, on niiden välinen korrelaatio myös pieni. Kyseisellä rakenteella on mahdollista toteuttaa säteilykuviodiversiteetti erittäin pienessä tilassa, kuten matkapuhelimessa. Toisaalta, kun yhdistetään kaksi QCA-elementtiä yhdeksi monielementtiratkaisuksi, voidaan toteuttaa laajakaistainen diversiteettiantenni, jonka suhteellinen -6 dB impedanssikaistanleveys on 87.5 %. Vastaavasti kahdella laajakaistaisella QCA-elementillä toteutetulla MIMO-ratkaisulla päästään 95 % suhteelliseen -6 dB impedanssikaistanleveyteen. Molemmilla ratkaisuilla on erittäin hyvät säteilyominaisuudet sekä alhainen korrelaatio ja pieni keskinäiskytkentä antennielementtien välillä. Suunniteltaessa toimivaa laajakaistaista antennirakennetta, on tärkeää ottaa huomioon antennisyötön impedanssisovitus, jotta antennin suorituskyky ei heikkenisi. Lisäksi balansoidussa rakenteissa tulee olla laajakaistainen baluni, jolla vältetään säteilykuvion vääristyminen. Väitöskirjan syöttöratkaisuissa on käytetty kaupallisia sähkömagneettisia simulaattoreita, joilla antennirakenne voidaan mallintaa kolmiulotteisesti, ja joilla laajakaistainen syöttö saadaan optimoitua haluttuun antenniin. Suurin osa esitellyistä antennirakenteista on simulointien lisäksi myös mitattu, jolloin niiden toimivuus käytännössä pystytään todentamaan rakentamalla prototyyppiantenni. Yleisesti väitöskirjassa esitellään tasomaisia antenniratkaisuja johtavassa maatasossa, joissa säteilevät pintavirrat herätetään mahdollisimman laajalla taajuusalueella. Ideana on löytää laajakaistaisia antenni- ja syöttörakenteita, joilla saadaan herätettyä perusmuoto tai jokin muu haluttu muoto. Ajatuksena on välttää korkeamman kertaluvun muotojen herättäminen, jotka voivat pilata antennin suorituskyvyn. Väitöskirjassa osoitetaan myös, että pienikokoisella antennilla on mahdollista herättää korkeamman kertaluvun muotoja pistetaajuudella käyttämällä useita heräte-elementtejä
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Tokgoz, Yeliz. "Performance analysis of antenna diversity based wireless communication systems /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2004. http://wwwlib.umi.com/cr/ucsd/fullcit?p3127633.
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Crummett, Ronald C., Michael A. Jensen, and Michael D. Rice. "TRANSMIT DIVERSITY SCHEME FOR DUAL-ANTENNA AERONAUTICAL TELEMETRY SYSTEMS." International Foundation for Telemetering, 2002. http://hdl.handle.net/10150/605606.
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International Telemetering Conference Proceedings / October 21, 2002 / Town & Country Hotel and Conference Center, San Diego, CaliforniaThe use of two antennas on an aeronautical telemetry transmitter is a common practice for overcoming signal obstruction that can occur during air vehicle maneuvering. However, this practice also leads to interference nulls that can cause dramatic degradation in the average signal integrity. This paper discusses the application of a transmit diversity scheme capable of overcoming this interference problem. The development leads to symbol error probability expressions that can be applied to assess the performance of the scheme relative to that of traditional schemes. Representative computational examples demonstrate the potential of the method.
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Lominé, Jimmy. "Étude d’une antenne vectorielle UHF multibande appliquée à la goniométrie 3D." Thesis, Toulouse, INPT, 2014. http://www.theses.fr/2014INPT0096/document.
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De nos jours, il existe de nombreuses antennes de radiogoniométrie UHF large bande ou multibandes, néanmoins très peu d’entre elles permettent une couverture angulaire 3D. A notre connaissance, la première antenne de radiogoniométrie 3D fût étudiée dans les années 1960, par une équipe de l’université du Michigan. Composée de 17 capteurs positionnés sur une surface hémisphérique, sa taille et son nombre d’éléments en font un dispositif encombrant et complexe à utiliser. De récentes études ont proposé une autre approche basée sur la mesure multicomposante du champ électromagnétique, permettant de réduire la taille des antennes et le nombre d’éléments tout en conservant une couverture angulaire 3D. Cependant, à ce jours, seul des systèmes HF (3MHz-30MHz) ou bande étroite ont été abordés. Cette thèse porte donc sur l’étude et le développement d’une antenne vectorielle UHF multibande appliquée à la radiogoniométrie 3D pour des ondes transverses magnétiques. Tout d’abord, deux techniques de goniométrie adaptées à cette approche sont confrontées : une nouvelle technique basée sur la décomposition en harmonique sphérique du rayonnement de l’antenne qui permet de recomposer le champ électromagnétique reçu à partir d’échantillons mesurés et un algorithme bien connu, MUSIC. Une méthodologie de conception est proposée, en identifiant les critères physiques des antennes vectorielles qui influent sur leurs performances à savoir la précision d’estimation, la sensibilité, le nombre d’éléments et l’encombrement. Cette méthode est utilisée pour développer et réaliser une première antenne vectorielle monobande. La caractérisation de cette antenne réaliste permet d’écarter la première technique de traitement dont les performances sont trop sensibles aux perturbations de rayonnement. Une antenne vectorielle bibande compacte, d’un rayon de λ/4 et d’une hauteur de λ/5.5 à la fréquence la plus basse, composée de seulement six éléments rayonnants couvrant chacun les bandes de fréquences GSM [890MHz-960MHz] et [1710MHZ-1880MHz] est ensuite développée en se basant sur cette méthode de conception. Les capteurs électriques et magnétiques constituant l’antenne sont étudiés séparément puis assemblés selon une répartition spatiale planaire pour restreindre l’encombrement. Les structures rayonnantes sont communes pour les deux bandes de fréquences ce qui permet réduire le nombre d’éléments ainsi que les éventuelles perturbations de rayonnement. Après la caractérisation de l’antenne bibande au travers de simulations numériques, un prototype est réalisé et ses performances d’estimation sont mesurées en chambre anéchoïque afin de valider l’approche par simulation. La sensibilité obtenue est de -110dBW/m² (85μV/m) pour une précision de 5° RMS. Enfin l’étude est élargie au cas général d’antennes multibandes en illustrant le processus d’extension de la couverture fréquentielle par l’ajout d’une troisième bande, [400MHz-430MHz]. Six nouveaux éléments sont donc développés et intégrés aux capteurs GSM existants afin d’obtenir une antenne tribande d’un rayon de λ/3.2 et d’une hauteur de λ/12.5 à 400MHz. Malgré une légère augmentation de l’erreur d’estimation, causée par la présence de ces nouveaux éléments, la caractérisation de cette nouvelle antenne tribande montre de bonnes performances d’estimation avec une sensibilité de -105dBW/m² (155μV/m) pour une précision de 5° RMSNowadays, a lot of wideband or multiband direction finding antennas operating in the UHF band exist. Nevertheless, only few of them allow to estimate the direction of arrival in the full 3D space. At the author’s knowledge, the first 3D direction finding antenna was studied in the 1960s, at the University of Michigan. Composed of 17 sensors, located on a large hemispherical surface, this antenna is bulky and complex to use. Recently, some studies have proposed another approach based on the multicomponent measurement of the electromagnetic field that allows to decrease the antennas size and the number of radiating elements without reducing the 3D angular coverage. However, only HF (3-30MHz) or narrowband systems have been reported. The objective of this PhD is to study and to develop an UHF multiband vector sensor applied to the estimation of the direction of arrival of transverse magnetic waves in the full 3D space. Firstly, two signal processing techniques adapted to this approach are compared : a new technique based on the spherical harmonic decomposition of the antenna radiation which allows to recompose the received electromagnetic field from the measured samples and a well-known high resolution algorithm called MUSIC. A design methodology allowing to identify the physical criteria of vector sensors related to the antenna performances such as the estimation accuracy, the sensitivity, the number of elements and the antenna size is proposed. This method is used for developing and designing a first single-band vector sensor. The results obtained from numerical simulations allow to rule out the first signal processing technique which is too sensitive to the radiation perturbations. Then, a compact dual-band vector sensor operating in the GSM frequency band, [890MHz-960MHz] and [1710MHZ-1880MHz], is developed by using the same design methodology. The antenna size is λ/4 in radius and λ/5.5 in height at the lowest frequency. The electric and magnetic elements which compose the vector sensors are designed separately and then combined according to a planar spatial distribution to retain a compact antenna size. The same radiating structures are used for operating in the two frequency bands in order to reduce the number of elements and the eventual radiation perturbations. After the performances assessment through numerical simulations in each band, a prototype is manufactured and its estimation performances are measured for a validation purpose. The sensitivity is -110dBW.m−2 (85μV.m−1) for a 5◦ RMS angular accuracy. Finally, the study is extended to the general case of multiband antennas by adding a third band, [400MHz-430MHz]. New elements are developed and incorporated into the dual-band GSM sensors to obtain a tri-band vector sensor. The size of this new antenna is λ/3.2 in radius and λ/12.5 in height at 400MHz. Despite a slight increase of the angular errors in the estimation of the direction of arrival caused by the presence of the new antenna elements, the characterization of the tri-band sensor performances by simulation show a good accuracy with a sensitivity valued at -105dBW.m−2 (155μV.m−1) for a 5◦ RMS angular accuracy
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Quist, Britton T. "Synthesis of Optimal Arrays For MIMO and Diversity Systems." BYU ScholarsArchive, 2007. https://scholarsarchive.byu.edu/etd/1244.
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This thesis proposes a method for determining the optimal antenna element radiation characteristics which maximize diversity gain given a specific power angular spectrum of the propagation environment. The method numerically constructs the eigenfunctions of the covariance operator for the scenario subject to constraints on the power radiated by each antenna as well as the level of supergain allowed in the solution. The optimal antenna characteristics are produced in terms of radiating current distributions along with their resulting radiation patterns. The results reveal that the optimal antennas can provide significantly more diversity gain than that provided by a simple practical design. Computational examples illustrate the effectiveness of adding additional elements to the optimal array and the relationship between aperture size or the description of the impinging field and the array performance. A synthesis procedure is proposed which uses genetic algorithm optimization to optimally place a reduced number of dipoles. The results from this procedure demonstrate that using the framework in conjunction with optimization strategies can lead to practical designs which perform well relative to the upper performance bound. Finally a novel array architecture is proposed where subsets of antennas are combined together into super-elements which are then combined in the same manner as the optimal array. The simplifications that result from the genetically optimized small array or the super-element array provide a design options which are feasible in many communication applications.
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Evans, Daniel N. "Near-Optimal Antenna Design for Multiple Antenna Systems." Diss., CLICK HERE for online access, 2009. http://contentdm.lib.byu.edu/ETD/image/etd2796.pdf.
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Duplouy, Johan. "Wideband Reconfigurable Vector Antenna for 3-D Direction Finding Application." Thesis, Toulouse, INPT, 2019. http://oatao.univ-toulouse.fr/24404/1/Duplouy_Johan.pdf.
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Direction finding plays a crucial role in various civilian and military applications, related to either radionavigation or radiolocation. Most of the direction finding antennas operate over a wide frequency band, but only a minority of them enable the direction of arrival estimation of an incoming electromagnetic field over a 3-D angular coverage (i.e., estimation of both azimuth and elevation angles). An original approach to obtain a 3-D angular coverage consists in measuring the six components of the incident electromagnetic field through a so-called vector antenna. The aim of this Ph.D. is to design a passive, compact and wideband vector antenna in order to cover a maximum of applications. Two vector antennas have been designed, manufactured and experimentally characterized. Unlike conventional topology, they enable the measurement of the components of an incoming electromagnetic field thanks to the radiation pattern reconfigurability of an original arrangement of Vivaldi antennas. The first prototype is mounted over a finite metallic support and enables the direction of arrival estimation of vertically-polarized electromagnetic fields over a 1.69:1 bandwidth while the second one can be used regardless of the polarization of the incoming electromagnetic fields over a 8:1 bandwidth. Moreover, the direction finding performances of these vector antennas have been improved in terms of estimation accuracy, sensitivity, robustness to angular ambiguity and polarization mismatch by synthesizing new radiation patterns in the estimation process. A method based on the Cramer-Rao lower bound has been proposed to select efficiently and rapidly the additional radiation patterns
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Aaberge, Tarjei. "Low Complexity Antenna Diversity For IEEE 802.15.4 2.4 GHz PHY." Thesis, Norwegian University of Science and Technology, Department of Electronics and Telecommunications, 2009. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-9942.
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This thesis investigates the obtainable performance improvements associated with different fading mitigation techniques using spatial antenna diversity applied to the IEEE 802.15.4 2.4 GHz PHY. The standard possesses modulation properties that inherently provide some multipath resistance. Further resistance is believed obtainable due to the bad and unpredictable fading environments found in typical areas of application. Potential performance increases were theoretically analyzed for different fading channel statistics when two antennas were available for reception. This analysis provided upper bounds for achievable performance improvements that were promising. Physical testing of selected fading mitigation techniques was performed with hardware from Texas Instruments and means developed by the student. Generally, the PHY has proven itself multipath resistant in the various fading environments tested. PER has been showed to mostly consist of undetected packets. As such, fading mitigation techniques using two receiver chains provide the greatest reduction in PER in a general case, since more packets are detected. PER is observed reduced by a test-dependant factor between 2 and 100 for such techniques. Techniques based on one RF-front end generally provides little performance improvement in dynamic environments, if any. Large spatial differences in received power were observed across distances on the order of a wavelength. A simple technique that switches receiver antenna when detecting an erroneously demodulated packet can exploit this property when RX and TX remain static and hence provide great reductions in PER. This fading mitigation technique is the least complex and power consuming among the ones analyzed and tested.
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Quist, Britton T. "Synthesis of optimal arrays for MIMO and diversity systems /." Diss., CLICK HERE for online access, 2006. http://contentdm.lib.byu.edu/ETD/image/etd2160.pdf.
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Jensen, Michael A., Michael D. Rice, Thomas Nelson, and Adam L. Anderson. "ORTHOGONAL DUAL-ANTENNA TRANSMIT DIVERSITY FOR SOQPSK IN AERONAUTICAL TELEMETRY CHANNELS." International Foundation for Telemetering, 2004. http://hdl.handle.net/10150/605320.
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International Telemetering Conference Proceedings / October 18-21, 2004 / Town & Country Resort, San Diego, CaliforniaTransmit diversity schemes such as the Alamouti space-time code have been shown to be viable candidates to enable robust dual-antenna transmission from maneuvering air vehicles. However, due to the complicated structure of shaped offset quadrature phase shift keying (SOQPSK) modulation, the Alamouti approach has not been applicable to SOQPSK systems. This paper develops a precoding and detection algorithm which allows implementation of dual-antenna Alamouti signaling for SOQPSK modulation. Performance simulations demonstrate the performance of the scheme for a realistic flight scenario.
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Anderson, Adam Lane. "Unitary Space-Time Transmit Diversity for Multiple Antenna Self-Interference Suppression." BYU ScholarsArchive, 2004. https://scholarsarchive.byu.edu/etd/154.
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A common practice for government defense agencies and commercial aeronautical companies is to use dual antennas on test flight air vehicles in order to overcome occlusion issues during high-speed telemetric maneuvers. The dual antennas, though never being masked at the same time, unfortunately lead to a drastic increase in nulls in the signal pattern. The result of this interference pattern can be compared to the effect of fading in a multiple-input multiple-output (MIMO) multi-path scattering environment. Confidence in this comparison leads to the use of unitary space-time MIMO codes to overcome the signal self-interference. The possibility and performance of several of these codes will be examined. Such criteria as training for channel estimation, use of shaped offset quadrature phase shift keying (SOQPSK), hardware facility, and data throughput will be compared for each code. A realistic telemetry channel will be derived to increase accuracy of simulated results and conclusions.
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Shen, Cheng. "Novel multiple antenna techniques for improved diversity in wireless communication systems." Thesis, Cardiff University, 2009. http://orca.cf.ac.uk/54840/.
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The focus of this thesis is to enhance the performance of wireless communication systems through the exploitation of multiple antennas at both the transmitter and the receiver ends of a communication link. Such a multiple-input multiple-output (MIMO) connection can theoretically provide spatially independent channels which can be exploited to provide diversity gain and thereby mitigate the problem of channel fading. To integrate such MIMO technology with emerging wireless systems such as third generation code division multiple access (CDMA) and fourth generation orthogonal division multiple access (OFDMA) based-approaches novel advanced signal processing techniques are required. The major advantages of MIMO systems, including array, diversity and multiplexing gains, are initially reviewed. Diversity gain is identified as the key property, which leverages the spatial independent channels to increase the robustness of the communication link. The family of space-time block codes is then introduced as a low computational complexity scheme to benefit from diversity gain within wireless systems. In particular, extended-orthogonal and quasi-orthogonal space-time block codes (EO-/QO-STBCs) are introduced for systems with four transmit antennas which can operate either in open or closed-loop forms. New EO-STBC and QO-STBC wideband CDMA transmission schemes are proposed which when operating in closed-loop mode, i.e. channel state information is exploited at the transmitter, is shown to attain full diversity and thereby outperform previous schemes in terms of attain able symbol error rate performance. This advantage is then utilized in MIMO-OFDM transmission schemes and similar frame error rate (FER) performance advantage is attained. Finally, to mitigate multiuser interference within the proposed MIMO-OFDM system a novel two-step combined parallel interference canceller and multiuser detection scheme is proposed. Simulation studies based upon FER confirm the efficacy of the technique.
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Dietrich, Carl B. "Adaptive Arrays and Diversity Antenna Configurations for Handheld Wireless Communication Terminals." Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/27291.
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This dissertation reports results of an investigation into the performance of adaptive beamforming and diversity combining using antenna arrays that can be mounted on handheld radios. Handheld arrays show great promise for improving the coverage, capacity, and power efficiency of wireless communication systems.
Diversity experiments using a handheld antenna array testbed (HAAT) are reported here. These experiments indicate that signals received by the antennas in two-element handheld antenna arrays with spacing of 0.15 wavelength or greater can be combined to provide 7-9 dB diversity gain against fading at the 99% reliability level in non line-of-sight multipath channels. Thus, peer-to-peer systems of handheld transceivers that use antenna arrays can achieve reliability comparable to systems of single-antenna handheld units, with only one-fifth the transmitter power, resulting in lower overall power consumption and increased battery life. Similar gains were observed for spatial, polarization, and pattern diversity.
Adaptive beamforming with single- and multi-polarized four-element arrays of closely spaced elements was investigated by experiment using the HAAT, and by computer simulation using a polarization-sensitive vector multipath propagation simulator developed for this purpose. Small and handheld adaptive arrays were shown to provide 25 to 40 dB or more of interference rejection in the presence of a single interferer in rural, suburban, and urban channels including line-of-sight and non line-of-sight cases. In multipath channels, these performance levels were achieved even when there was no separation between the transmitters in azimuth angle as seen from the receiver, and no difference in the orientations of the two transmitting antennas. This interference rejection capability potentially allows two separate spatial channels to coexist in the same time/frequency channel, doubling system capacity.Ph. D.
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Yan, Kai. "Genetic algorithm assisted CDMA multiuser detection." Thesis, University of Southampton, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343015.
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Mysore, Naveen. "Combined turbo coding and turbo equalization for wireless systems with antenna diversity." Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=33983.
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Emerging wireless communication systems strive for very high data rates, increased coverage and good quality of service. To achieve these goals under harsh conditions on many wireless channels (e.g., due to fading, multipath interference, power constraints and bandwidth limitations), both antenna diversity schemes and channel coding should be utilized.This thesis focuses on achieving reliable transmission over a class of multi-input multi-output Rayleigh faded channels at very low Signal-to-Noise Ratios (SNRs). The transmitter and receiver designs are based on turbo coding, multiple transmit/receive antennas and turbo equalization. Simulation studies were performed for systems with different coding rates, numbers of antennas and interleaving strategies. They show the ability to achieve small bit error rates (10-4--10-5) for negative values of SNR.
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Chan, Lewis C. H. "Reduced-search sequence decoders for multiple-antenna diversity over Rayleigh fading channels." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0001/MQ28184.pdf.
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Meshkati, Farhad. "Chip equalization and transmit antenna diversity for high-speed SS/TDM systems." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/MQ63022.pdf.
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Chiau, Choo Chiap. "Study of the diversity antenna array for the MIMO wireless communication systems." Thesis, Queen Mary, University of London, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.428692.
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Glasgow, Telbert R. "An investigation into antenna diversity for handheld transceivers in mobile radio communications." Thesis, University of Southampton, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303105.
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Jung, Chang won, Ming-jer Lee, Sunan Liu, G. P. Li, and Flaviis Franco De. "RECONFIGURABLE PATCH ANTENNA FOR FREQUENCY DIVERSITY WITH HIGH FREQUENCY RATIO (1.6:1)." International Foundation for Telemetering, 2005. http://hdl.handle.net/10150/605028.
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ITC/USA 2005 Conference Proceedings / The Forty-First Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2005 / Riviera Hotel & Convention Center, Las Vegas, NevadaReconfigurable patch antenna integrated with RF mircoelectromechanical system (MEMS) switches is presented in this paper. The proposed antenna radiates circularly polarized wave at selectable dual frequencies (4.7 GHz and 7.5GHz) of high frequency ratio (1.6:1). The switches are incorporated into the diagonally-fed square patch for controlling the operation frequency, and a rectangular stub attached to the edge of the patch acts as the perturbation to produce the circular polarization. Gain of proposed antenna is 5 - 6dBi, and axial ratio satisfies 3dB criterion at both operating frequencies. The switches are monolithically integrated on quartz substrate. The antenna can be used in applications requiring frequency diversity of remarkable high frequency ratio.
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Uribeetxeberria, Roberto. "Adaptive space diversity and ring coding for multicarrier CDMA over mobile radio channels." Thesis, Staffordshire University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343385.
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Ikai, Youhei, Masaaki Katayama, Takaya Yamazato, and Akira Ogawa. "Code Acquisition of a DS/SS Signal with Transmit and Receive Antenna Diversity." IEICE, 1999. http://hdl.handle.net/2237/7219.
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Sayago, Montilla David. "The Plausibility of implementing Receive Antenna Diversity in the Downlink of CDMA450 system." Thesis, University of Gävle, Ämnesavdelningen för elektronik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-6666.
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Barbosa, Nogueira Evanaska Maria. "Conception d'un système d'antennes pour la localisation en temps réel avec réseau de capteurs sans fils." Phd thesis, Université de Grenoble, 2013. http://tel.archives-ouvertes.fr/tel-00981583.
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Les systèmes de localisation en temps réel (Real-Time Locating System - RTLS) sont de plus en plus employés dans l'industrie. Ils permettent l'automatisation de diverses tâches telles que l'identification et le suivi des objets au long de la chaîne d'approvisionnement, la surveillance d'équipements dans les usines et la sécurisation des biens. Ces systèmes sont basés sur des capteurs électroniques sans fil à faible puissance et à faible coût avec des antennes intégrées. Dans notre contexte, deux types de capteurs sont utilisés. Les tags de référence sont généralement fixés sur les murs tandis que les tags mobiles sont fixés sur les objets qui doivent être suivis. Notre système RTLS (Real Time Localisation System) exploite la puissance du signal reçu (Received Signal Strength Indication - RSSI) pour calculer la localisation des tags mobiles. Toutefois, la performance de ce système peut être influencée par plusieurs facteurs. Tout d'abord, par rapport à l'antenne, la non-uniformité du diagramme de rayonnement et le non-alignement de la polarisation des antennes peuvent affecter la puissance du signal reçu. De plus, l'impact de l'environnement résulte sur des multi-trajets qui dégradent la précision de la localisation. Dans la première partie de ce travail, nous proposons une solution pour le tag de référence en utilisant un plan réflecteur en métal pour améliorer son diagramme de rayonnement. Nous avons effectué plusieurs expériences utilisant un logiciel de simulation et nous démontrons que l'utilisation d'un plan réflecteur en métal améliore considérablement la précision de la localisation de notre système. Dans la deuxième partie, nous proposons d'utiliser des techniques de diversité d'antenne pour le tag mobile afin de minimiser les effets des multi-trajets et d'améliorer le diagramme de rayonnement afin de couvrir tout l'espace souhaité pour la localisation. Nos solutions se composent de trois antennes intégrées sur le boîtier en plastique du tag, alliant la diversité de diagramme et de polarisation. Nous proposons une première structure avec trois antennes PIFAs manufacturées et fixées à l'extérieur du boîtier, un deuxième système avec deux antennes IFAs et enfin une antenne patch triangulaire sur un substrat permettant de plier les antennes, de façon à pouvoir rentrer la structure dans le boîtier du tag. Ces systèmes ont été simulés dans différents configurations de scénario afin de valider l'amélioration apportée par nos solutions. Finalement, des expérimentations ont été menées afin de comparer les systèmes proposés dans un environnement réel. Les résultats montrent que l'erreur de localisation a été divisée par un facteur proche de trois par rapport au système d'origine.
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Bae, Kyung Kyoon. "Analytical Framework for the Performance Analysis of Multiple Antenna Systems." Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/29212.
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There has been great interest in antenna array processing (diversity, beamforming, null steering, and spatial multiplexing) to enhance the received signal quality and the capacity of
wireless communications systems. However, in order to properly exploit the characteristics of different array processing techniques, understanding trade-offs among different techniques and parametric investigation, which offers an insight as to what parameters determine system performance under different situations
is necessary. In this study, we present analytical framework which can facilitate the performance analysis of systems with antenna
array.
Five original contributions to the performance analysis of antenna array processing are presented in this study. First, we present theoretical outage probability of a system equipped with an array which suppresses a few dominant interering signals in TDMA cellular networks when the fading statistics of interfering
signals are independent but non-identically distributed. Most of the related previous works assumed either independent and identically distributed fading statistics among cochannel
interferences (CCI) or Rayleigh fading when CCI signals are subject to i.n.d. fading statistics. Secondly, the performance of multi-branch predetection equal gain combiner for different
modulation techniques in equally correlated Nakagami-$m$ fading is presented through analytical analysis. Specifically, the
characteristic function (CHF) and the moment generating function (MGF) of EGC output with correlated inputs are derived and used to evaluate the average symbol error probability (ASEP) and the outage probability performance, respectively. Thirdly, we derived analytical expression which can be used to analyze the
performance of different types of diversity techniques in equally correlated Nakagami-m or Rice fading channels. Fourthly, asymptotic analysis on different types of diversity combiners in generalized fading channels is presented in a unifying way. Finally, we investigate and present the impact of transmit
diversity at handsets on the reverse link DS/CDMA systems in terms of capacity and coverage over generalized fading channels through analytical approaches. Then, we validate the analytical results with simulation results and investigate practical issues which are hard to capture through analytical analysis using system level
simulator we developed.
Although we have mainly focused on applying the analytical framework we have derived in this work to the performance analysis of physical layer algorithms such as spatial diversity and
adaptive null steering, the framework can be extended to assist the analysis and design of wireless communication systems such as,
to name a few, distributed multiple input multiple output (MIMO) system in cooperative wireless networks, multipath routing protocol analysis in wireless fading channels, and antenna
selection problems in MIMO system.Ph. D.
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Sfar, Sana. "Multiple array schemes for achieving high capacity and high diversity gains in wireless MIMO systems /." View abstract or full-text, 2005. http://library.ust.hk/cgi/db/thesis.pl?ELEC%202005%20SFAR.
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Kim, Byung-ki. "Smart Base Station Antenna Performance for Several Scenarios - an Experimental and Modeling Investigation." Diss., Virginia Tech, 2002. http://hdl.handle.net/10919/11043.
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Smart antenna systems are employed to overcome multipath fading, extend range, and increase capacity by using diversity or beamforming techniques in wireless communication systems. Understanding of the smart base antenna performance mechanisms for various environments is important to design cost effective systems and network. This dissertation focuses on the experimental characterization and modeling of the smart base station antenna performance for various propagation environment scenarios.
An eight-channel Virginia Tech smart base station antenna testbed was developed to investigate performances of three reverse link diversity methods. The experiment campaign resulted in 245 sets of collected data over 83 measurement sites, which were used to compare the performance of space, polarization, and angle diversity under identical conditions. Measured propagation path loss, envelope correlation coefficients, power imbalances, and mean effective gain (MEG) are characterized as a function of distance between the base station and the mobile terminal to illustrate the diversity performance mechanisms over different propagation environments. The performance of the three base station diversity methods with selection combining (SC), maximal ratio combining (MRC), and equal gain combining (EGC) techniques for both urban and suburban non-line-of-sight (NLOS) environments are presented and summarized using the measured data.
Forward-link performance of a twelve-fixed narrow-beam base station antenna system for urban NLOS environments is investigated using the same measured data. A new procedure is introduced to experimentally model the forward-link performance of muitlple-fixed narrow-beam (MFNB) antennas using the measured reverse-link vector channel response. The experimentally calculated lower bound performance result shows that it achieves 2.5 to 2.8 times higher average RF SIR compared to the conventional three-sector base station system for typical urban NLOS multipath fading environment conditions. Also, a new mobile user angle estimation algorithm using the muitlple-fixed narrow-beam antennas for NLOS multipath fading environment conditions is developed and the experiment results are presented.Ph. D.
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Sandhu, Waseem Hussain, and Muhammad Awais. "MULTIPLE ANTENNA TECHNIQUES IN WiMAX." Thesis, Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-1120.
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Now-a-days wireless networks such as cellular communication have deeply affected human lives and became an essential part of it. The demand to buy high capacity and better performance devices and cellular services has been rapidly increased. There are more than two hundred different countries and almost three billion users all over the world which are using cellular services provided by Global System for Mobile (GSM), Universal Mobile Telecommunication System (UMTS), Wireless Local Area Network (WLAN) and Worldwide Interoperability for Microwave Access (WiMAX). In the past decade, one antenna is connected to only one communication radio device at the same time but currently this scenario has been completely changed. To increase the capacity of the channels and to improve the bit error performance between mobile station and service station, it is now possible to connect one antenna with more than one communication radio device at the same time. Multiple Input Multiple Output (MIMO) systems are designed to obtain this requirement. In MIMO systems, antennas are combined in the form of small frames like coupling in cellular devices. Diversity means to obtain successful transmission and reception of radio signals with accordance to polarization and correlation. Due to diversity the capacity of the channels and bit error rate are improved, so diversity is one of the main and important properties of MIMO systems. This thesis is emphasized to study WiMAX systems by implementing multiple antenna techniques, by observing the bit error rate performance and data rate in WiMAX systems using two important and currently widely applied multiple access communication techniques. The research will also elaborate these techniques and explain the basic parameters, operations, mathematical calculations and different relevant observations. The simulation tool used in this research thesis is MATLAB which is also used to illustrate the results with figures and graphs.Nu för tiden trådlösa nätverk såsom cellulär kommunikation har stor påverkan på människors liv och blev en viktig del av det. Kravet att köpa hög kapacitet och bättre utrustning prestanda och mobiltelefoni har snabbt ökat. Det finns mer än två hundra olika länder och nästan tre miljarder användare över hela världen som använder mobiltelefoni som Global System for Mobile (GSM), Universal Mobile Telecommunication System (UMTS), Wireless Local Area Network (WLAN) och Worldwide Interoperability för Microwave Access (WiMAX). Under det senaste decenniet har en antenn ansluten till en kommunikationsradio enhet vid samma tidpunkt, men för närvarande detta scenario har fullständigt förändrats. Att öka kapaciteten av kanalerna och för att förbättra prestandan lite fel mellan mobil station och bensinstationen, är det nu möjligt att ansluta en antenn med mer än en kommunikationsradio enhet samtidigt. Multiple Input Multiple Output (MIMO) system är utformade för att uppnå detta krav. I MIMO-system, antenner kombineras i form av små ramar som kopplingsanordningar i cellulär enheter. Mångfald innebär att få lyckad överföring och mottagning av radiosignaler i enlighet med polarisation och korrelation. På grund av mångfalden kapacitet av kanalerna och bit error rate förbättras, så att mångfald är en av de största och viktigaste egenskaper MIMO-system. Denna avhandling är betonas att studera WiMAX system genom att genomföra flera antenn teknik, genom att observera bitars prestanda felfrekvensen och datahastighet i WiMAX system med hjälp av två viktiga och som för närvarande tillämpas allmänt flera tekniker tillgång kommunikation. Forskningen kommer också att utveckla dessa metoder och förklara de grundläggande parametrarna, operationer, matematiska beräkningar och olika relevanta iakttagelser. Den simuleringsverktyg som används i denna forskning avhandling är MATLAB som också används för att illustrera resultaten med siffror och diagram.
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Jensen, Michael A., Michael D. Rice, and Adam L. Anderson. "COMPARISON OF ALAMOUTI AND DIFFERENTIAL SPACE-TIME CODES FOR AERONAUTICAL TELEMETRY DUAL-ANTENNA TRANSMIT DIVERSITY." International Foundation for Telemetering, 2004. http://hdl.handle.net/10150/605313.
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International Telemetering Conference Proceedings / October 18-21, 2004 / Town & Country Resort, San Diego, CaliforniaThe placement of two antennas on an air vehicle is one possible practice for overcoming signal obstruction created by vehicle maneuvering during air-to-ground transmission. Unfortunately, for vehicle attitudes where both antennas have a clear path to the receiving station, this practice also leads to self-interference nulls, resulting in dramatic degradation in the average signal integrity. This paper discusses application of unitary space-time codes such as the Alamouti transmit diversity scheme and unitary differential space-time codes to overcome the self-interference effect observed in such systems.
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JAIN, VISHESH. "PERFORMANCE ANALYSIS OF GENERALIZED SELECTION COMBINING IN ARBITRARILY CORRELATED NAKAGAMI FADING CHANNELS." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1131175492.
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Dietze, Kai. "Analysis of a Two-Branch Maximal Ratio and Selection Diversity System with Unequal Branch Powers and Correlated Inputs for a Rayleigh Fading Channel." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/32412.
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This report, presents an analytical framework for analyzing two-branch diversity systems for a Rayleigh fading channel. In many cases the fading received at both branches (i.e. a two-antenna element system) is correlated because of the proximity of the antenna elements to each other. It is also not uncommon for a diversity system to use antennas with different patterns or polarizations, this usually results in differences in average signal-to-noise ratios at both branches depending on which element is better matched to the signal environment. As will be shown, the performance of a diversity system depends greatly on the envelope correlation, average power imbalance and the combining scheme used on both branches.
An analytical expression for the probability density function of the signal-to-noise ratio at the output of a two-branch maximal ratio and selection diversity system is developed in this report. The two branches are assumed to be Rayleigh fading, correlated, as well as of unequal signal-to-noise ratios. Measurements were made in Rayleigh fading channels and compared to the analytical results. The analytical cumulative distribution functions (derived using probability distributions) were found to be within 1 dB of the measured results (statistics obtained from time combining) for both maximal ratio and selection diversity attesting to the validity of the analytic results. Also developed in this report are the exact analytical average probabilities of symbol error for coherent BPSK and coherent QPSK before and after maximal ratio combining for this environment. The diversity gain for selection, maximal ratio, and equal gain combining for the 10% probability level is presented as a function of power imbalance and correlation between branches for a two-branch Rayleigh diversity systemMaster of Science
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Dai, Bang-Yun, and 戴邦雲. "Design of Diversity Antennas on Mobile Terminals and Development of Antenna Diversity Measurement System." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/55858101431222806421.
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碩士國立臺灣科技大學
電機工程系
103
This thesis is focused on the development of an antenna measurement system and a broadband antenna applicable for LTE uses. The first part is about a low-cost, semi-automatic effective diversity gain measurement system for multi-antenna systems. It comprises a transmitter and a receiving end. Continuous waves are provided by a signal generator and emitted from a reference antenna. The receiving end contains a control computer, a multi-channel data acquisition card, RF power detectors, and the multi-antenna system under test. The system can automatically read and record the data. Measurements of basic diversity antenna setups as well as multi-antenna systems were tested to validate the effectiveness of the proposed approach. Comparing to existing diversity evaluation methods, this approach provides not only convincing results but also saves a lot in time and cost. The second part is about a two-antenna system for LTE MIMO uses on tablets. To be integrated within slim portable devices, the proposed antenna is made with a flexible printed circuit board. The antenna structure is simple, which is a folded metal sheet with slots. It provides very broad operation bands. Commonly used LTE bands including 690 to 960 MHz and 1710 to 2690 MHz bands are covered with decent matching and radiation characteristics. A two-antenna displacement scheme on tablet is proposed with a fair isolation performance. The defected ground structure technique is employed to further reduce antenna coupling. Performance features such as radiation patterns, envelope correlation coefficient and effective diversity gain are measured. All the results validate that it is suitable for MIMO uses.
48
Tsai, Wen-Tsai, and 蔡文才. "Design of Commercial Microstrip Antenna and Antenna Diversity." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/60472419077116045622.
Full textAbstract:
碩士逢甲大學
電機工程所
92
In this thesis, the meander-line antenna, the novel slot antenna and the feeding module of diverse antenna for the WLAN applications have been implemented and investigated. The simulated and measured results of the radio-frequency circuits and the antennas are detailed and analyzed. First, three miniaturized planar meander-line antennas have been proposed and presented for the applications of the dual bands (GSM and DCS). The two-arm meander-line antenna, one with a patch and one with a rectangular loop are fabricated and tested. The advantages of the antennas are to lower the circuit cost, lower the antenna height, save the process time, reduce the number of via holes and simplify the mechanical construction. The size reduction is achieved by folding the antenna trace, a monopole, on the FR4 substrate. The measured data presents that the bandwidths of the original meander-line antenna in the talking position achieved were 215 MHz and 279 MHz at 900 and 1800-MHz, respectively. The comparison of the radiated powers of the three topologies of the meander-line antenna was also presented. The loading effects of the outside environments surrounding the meander-line antennas were also discussed. Second, we present two practical techniques to modify the operating frequency, enhance the bandwidth and miniaturize the antenna size for microstrip-fed slot antennas at the 2.4 GHz and 5 GHz (the industrial-scientific-medical (ISM) bands and the Hiper-LAN). Four slot antennas were fabricated, measured and compared to demonstrate the capability by adding several tuning stubs at the edge of the radiated slot and utilizing the Z-like slot (a novel slot antenna) instead of the conventional rectangular-shaped slot. The Z-like slot antenna (a novel slot antenna) not only reduces the upper resonant frequency and enlarges the bandwidth of the lower resonant band, but the antenna size is also reduced by 10%, approximately. Finally, a microstrip feeding module for the pattern diversity of the dual-band wireless local-area network (WLAN) applications has been designed, fabricated and measured. A feeding module includes a power divider and a switch module. The wideband Wilkinson power divider with the defected-ground structure (DGS) is integrated with the dual-band single-port-double- throw (SPDT) switch module to provide two individually signal paths for the inputs of the two-element antenna array. Several practical techniques are used to improve the impedance bandwidth and enhance the efficiency of the output power. By changing the bias voltages of the FET devices, the system switching between the array’s two ports has been operated such that the maximum signal strength for the positioning function of the access point or repeater can be demonstrated.
49
Tsai, Hsiao-ping, and 蔡曉萍. "WLAN Polarization Diversity Antenna Design." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/90585781163752767211.
Full textAbstract:
碩士國立臺灣大學
電機工程學系
85
In an indoor radio environment plagued by the severe spatial fading and temporal fading effects of multipath, diversity schemes usually required. This thesis proposes a flat diversity antenna, consisting of two cross-polarized dipole antennas selectly excited by a PIN diode at the feeding point, to reduce the fading effects in the indoor environment. Results presented here provide a comparison between measurement and simulation results of input impedance and radiation pattern. Parameters studies of the antennas are also presented. To verify the diversity effects of this antenna, measurement for propagation characteristics was made in one of NTU EE laboratories at 2.4 GHz. The diversity gain is forward to be at least 3dB at 99% signal availability.
50
Lu, Zih-Hao, and 盧子豪. "Design and Analysis of Compact Antennas and Diversity Antenna for Wireless Communication." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/41521658313880477229.
Full textAbstract:
碩士國立臺北科技大學
電腦通訊與控制研究所
92
In this thesis, we will discuss two topics about antennas. First, the slow wave effects will be used to design the compact antenna. The elementary structure of the compact antenna is that shorting and feeding positions are located respectively on both sides of the designed antenna. The slow wave effect will be introduced by etching applicable geometric figures on radiator of the antenna and the slow wave effect can be changed by adjusting the etching position. The measurement results show that the significant slow wave effect is introduced, if the etching geometric figure on the radiator of the antenna is placed at the position where has large the current density. Then more obvious slow wave effect introduces the lower relative resonant frequency. So the antenna size can be reduced significantly by the introduction of slow wave property. Also, modifying the width and height of antenna is alternative way to reduce the size of antenna. The other topic about antenna presented in this thesis will study two configurations of switched-beam diversity antennas for wireless communication. In the first configuration, two patch antennas separating form a two elements antenna array. The feeding phases of each antenna element can be changed from in-phase to out-of phase by switching the appropriate pin-diodes on-off status. Then the array factor of the patch antenna array can be changed from end-fire direction to broadside direction. In the second configuration, two thin conductors are put on both sides of one dipole antenna and the both distances between each thin conductor and the dipole antenna are set as . For each thin conductor, there is a break point on the middle, then mount a pin-diode on the break point. Because the length of two thin conductors are longer than the length of the dipole antenna, two thin conductors will be equivalent as inductive reflector or capacitive reflector by switching the pin-diode to on or off status respectively. Hence, the main beams of this configuration can be switched and almost have 180o difference. For the above mentioned two configurations, the experiments show the switched-beams have low correlation coefficients 0.0318 and 0.0837 respectively. Only one feeding port is needed to configure the switched-beam antennas and the small distance between the array elements is needed to provide enough low correlation for the proposed configurations. These above mentioned antenna configurations are suitable to design the practical wireless communication systems. This is major contributions in this thesis.