A compact multiband antennas for Long Term Evolution (LTE) applications is a challenge. Both the frequencies of new wireless technologies and new frequency bands must be covered. The lower end of the 0.7- 3.5 GHz band is especially difficult to handle for miniaturized terminal devices. A single layer, line-feed rectangular microstrip patch antenna is small enough for the LTE handsets. Our project proposes size reduction and bandwidth enhancement through adapted feeding techniques. By means of slits the return loss and gain can be optimized with the aid of HFSS (High Frequency Structure Simulator).

In this work we investigated a new class of subwavelength focusing device, termed the holographic metallic screen. We first proposed a generalized procedure which takes a holographic record of a subwavelength electromagnetic field distribution. Subsequently we synthesized this record using two types of holographic metallic screen – the slot antenna hologram (SAH) and the resonant slot antenna hologram (RSAH). We designed both holograms and evaluated their performances through full-wave simulations, and experimentally demonstrated subwavelength focusing for the RSAH. Simulations and experiments illustrated various attractive properties of the subwavelength focusing RSAH, which included (a) a tighter focal width than a single subwavelength aperture; (b) a focal field amplitude surpassing the incident field amplitude; and (c) a simple design scalable to a wide range of frequencies from microwave to optical. These properties should serve to motivate further development on the holographic metallic screen towards potential applications such as sensing, imaging and lithography.

Les tecnologies sense fils han provocat una important revolució en el món de les xarxes i serveis de telecomunicació. Han apareguts nous sistemes com els telèfons mòbils d'última generació o les xarxes LAN sense fils que han estat acceptats amb entusiasme per la població. En particular, l'ús de xarxes de sensors (per controlar la temperatura, per a detectar places lliures d'aparcament, etc.) està creixent ràpidament . Aquesta tesi es centra en el disseny d'antenes per a xarxes de sensors distribuïts. En concret s'analitza un sistema on els sensors remots estan connectats a una unitat central utilitzant un radio enllaç operant en la banda ISM de 5,8 GHz, i la unitat central envia la informació recollida a Internet a través d'una connexió WLAN. A la unitat central es necessiten antenes multibanda per cobrir diverses bandes de freqüències amb un únic element radiant. En aquesta tesi es presenten dues solucions per obtenir aquest comportament multibanda: Monopols amb pla de massa fractal i monopols carregats amb ressonadors. S'han fabricat i mesurat diferents prototips que cobreixen les necessitats del sistema. Els sensors han de ser dispositius de reduïdes dimensions i baix cost. Una bona opció per aconseguir aquests requisits és l'ús d'antenes integrades en silici fabricades amb una tecnologia CMOS estàndard. En primer lloc s'analitzen els principals problemes de la integració de l'antena en silici, i a continuació es presenta una possible solució per millorar l'eficiència juntament amb un estudi de la degradació introduïda per altres components quan aquests es fabriquen en el mateix xip que l’antena. Les mesures dels prototips fabricats demostren que la integració de l'antena en la banda de 5,8 GHz és factible, obtenint un abast d'alguns metres. Cada vegada és una realitat més propera el fet de tenir sensors implantats en el cos. Per aquest motiu, l’última part d'aquesta tesi es dedica a estudiar els efectes del cos sobre antenes situades en el seu interior i avaluar les pèrdues de propagació addicionals introduïdes pels teixits humans. / Las tecnologías inalámbricas han provocado una importante revolución en el mundo de las redes y servicios de telecomunicación. Han aparecidos nuevos sistemas, como los teléfonos móviles de última generación o las redes LAN inalámbricas, que han sido aceptados con entusiasmo por la población. En particular, el uso de redes de sensores (para controlar la temperatura, para detectar plazas libres de aparcamiento, etc.) está creciendo rápidamente. Esta tesis se centra en el diseño de antenas para redes de sensores inalámbricos distribuidos. EN concreto se analiza un sistema donde los sensores están conectados a una unidad central utilizando un enlace inalámbrico en la banda ISM de 5.8 GHz, y la unidad central envía la información recogida a Internet a través de una conexión WLAN. En la unidad central se necesitan antenas multibanda para dar servicio a varias bandas de frecuencias con un único elemento radiante. En esta tesis se presentan dos soluciones para obtener este comportamiento multibanda: Monopolos con plano de masa fractal y monopolos cargados con resonadores. Se han fabricado y medido diferentes prototipos que cubren las necesidades del sistema. En los sensores se desean dispositivos de reducidas dimensiones y bajo coste. Una buena opción para lograr estos requisitos es el uso de antenas integradas en silicio fabricadas con una tecnología CMOS estándar. En primer lugar se analizan los principales problemas de la integración de la antena en silicio, y a continuación se presenta una posible solución para mejorar la eficiencia de radiación junto con un estudio de la degradación introducida por otros componentes cuando éstos se fabrican en el mismo chip que la antena. Las medidas de los prototipos fabricados demuestran que la integración de la antena en la banda de 5,8 GHz usando una tecnología CMOS es factible, obteniendo unos alcances de algunos metros incluso cuando la antena se fabrica junto con otros elementos integrados en el mismo chip. Cada vez es una realidad más cercana el hecho de poder tener sensores implantados en el cuerpo. Por este motivo, la última parte de esta tesis se dedica a estudiar los efectos del cuerpo sobre antenas situadas en su interior y evaluar las pérdidas de propagación adicionales introducida por los tejidos humanos. / Wireless technologies have triggered an important revolution in the world of telecommunication networks and services. New systems, such as the latest generation mobile phones or wireless LANs, have appeared being enthusiastically accepted by people. In particular, applications related to remote sensor networks are growing rapidly (for temperature monitoring, the detection of free parking spaces, etc.). This thesis is focused on antenna design for distributed wireless sensor networks. The remote sensors we are considering are connected to a central unit using a wireless link in the 5.8 GHz ISM band and the central unit transmits the collected information to the Internet via a WLAN connection. In the central unit multiband antennas are necessary to cover several frequency bands with a single radiating element. Two solutions to obtain this multiband performance are proposed: fractal-based ground planes and resonator loaded monopoles. Several novel antennas that easily meet the system requirements are manufactured and measured. For remote sensors small dimensions and low costs are desired. The use of silicon integrated antennas fabricated with standard CMOS technology is a good choice to achieve these requirements. First, the main problems of antenna integration are discussed and, then a possible solution to improve the antenna efficiency is presented together with a study of the effects of other elements integrated in the same chip with the antenna. The measurements of the manufactured prototypes demonstrate that antenna integration at 5.8 GHz is feasible, and that system ranges of some meters can be obtained even when the antenna is fabricated together with other elements integrated in the same chip. The possibility of having some of the sensors implanted inside the body will be a reality in the near future, for this reason the particular case of implanted antennas is also analyzed. The last part of this thesis is devoted to study the body effects on antenna performance and evaluate the additional propagation losses introduced by the body tissues.

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.

This report presents concepts for a planar active electronically scanned antenna(AESA). The goal of the project was to devlop a low-weight, low profile, thin, S-band antenna with wide-scan angle capabilities. In the final concept the service aspects of the T/R-modules was also taken into acount in order to allow easy and fast replacements of these components. The antenna was designed and optimised using the commercial software Ansoft HFSS. A prototype of the antenna was constructed and later measured and verified. The final concept is a 2m×2m antenna with an estimated weight of around 320 kg, around 11 cm thick (where the thickness of the antenna element is 1.76 cm) and has a maximum scan angle range of more than 45 degrees (with <–10dB active reflection) in the frequency band 3–3.5 GHz.

This thesis describes the investigation of photonic crystals as a substrate in microstrip phased array antennas. Alumina with a relative dielectric constant of 9.6 is used as substrate to obtain miniaturization of the components in the high-frequency range. The proposed design consists of four rectangular patches in a linear array conguration operating at 12 GHz. The antenna elements are excited by a microstrip feed line using the inset feeding technique for perfect impedance matching. A beam steering of 20o is achieved using a switched line phase shifter. Antenna parameters, including impedance matching, bandwidth, gain, directivity and the S parameters of the proposed array antenna are obtained. The simulation results are obtained with the Advanced Design System (ADS) simulator.

Cylindrically conformal microstrip antennas are investigated. Two different structures, namely proximity coupled and E-shaped microstrip antennas are analyzed and information about the design parameters is obtained by means of parametric study. With these structures, cylindrical arrays, having omnidirectional radiation in the circumferential plane of the cylinder, are designed. Proximity coupled cylindrical arrays operate in the 2.3-2.4 GHz aeronautical telemetry band with approximately 4% bandwidth. On the other hand, more than 30% bandwidth is obtained by E-Shaped cylindrical array antenna structure, which also includes the commercial telemetry band. In order to verify the simulation method, a fabricated antenna in literature is simulated and acceptable agreement with simulation and fabrication results obtained.

Thesis--Auburn University, 2009. / Abstract. Vita. Includes bibliographic references (p.49-51).

In this thesis the possibility of building an underwater communication system usingelectromagnetic waves has been explored. The focus became designing and testingan antenna even if the entire system has been outlined as well. The conclusion isthat using magnetically linked antennas in the near field it is a very real possibilitybut for long EM waves in the far field more testing needs to be done. This isbecause a lack of equipment and facilitates which made it hard to do the realworld testing for this implementation even if it should work in theory.

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