With the fast adoption of LTE and IEEE 802.11N, more devices are employing multiple antennas to boost the data rate and reliability of the communication link. Traditionally, fixed antennas are used in such devices. In recent years, reconfigurable antennas have been sought out to further boost the performance, which can adaptor to the changing wireless channel by altering their radiation characteristics, and maintain or exceed the performance of fixed antennas. This thesis studies the possibility of performance increase using pattern reconfigurable antennas as receivers. Their performance potential was first estimated using simulations, and then demonstrated using two electrically steerable passive array radiator (ESPAR) antennas against a pair of monopole antennas on a hardware bit error rate (BER) testbed. The former produces equal performance in BER with certain pattern combinations and excels in theoretical capacity with substantial lead making pattern reconfigurable antenna a potent option as receiver in MIMO-related applications.

Reconfigurable radio frequency (RF) devices are attractive for miniaturization of wireless components and systems by handling functionality of multiple distinct devices. Existing reconfiguration techniques rely on device loadings with semiconductor diodes, ferrite/ferroelectric materials, and microelectromechanical system (MEMS) switches and capacitors. However, it is well-recognized that these techniques cannot fully address important system metrics such as high efficiency, wide frequency tuning range, high power handling capability and cost. Therefore, novel alternative techniques are highly desirable to advance the state of the art in reconfigurable RF devices. The aim of this dissertation is to investigate the novel concept of microfluidically loaded reconfigurability within the context of RF antennas and imaging systems. The proposed devices operate based on continuously movable microfluidic loads consisting of metal (liquid/solid) and dielectric solutions. Microfluidics and microfabrication techniques are utilized with flexible/rigid multilayered substrates to maximize the reconfigurable loading effect on the devices and enable highly reconfigurable antennas and imaging array realizations. Specifically, a wideband frequency tunable monopole antenna is introduced by utilizing continuously movable liquid metal within the microfluidic channel as a length varying conductor. By resorting to ultra-thin channel walls, the liquid metal volume overlapping with the microstrip line feed is utilized as a non-radiating capacitive excitation point to achieve the realized 4:1 (1.29GHz – 5.17GHz) frequency tuning range. Subsequently, an alternative design that replaces liquid metal volume with a microfluidically movable metallized plate is introduced. This novel liquid-metal-free implementation alleviates the liquid metal associated drawbacks of reliability, long-term device operation, and efficiency. The antenna is shown to provide 2:1 (1.6GHz – 3.5GHz) frequency tuning range with > 87 % radiation efficient. Due to the high radiation efficiency, the antenna is also capable of handling 15 W of RF power which is 10 W more than its liquid metal counterpart. This metallized plate approach is also suitable for reconfiguration of miniature antennas, and this is demonstrated with the design/implementation of a microfluidically reconfigurable top loaded monopole antenna. It is also suitable for reconfiguration of other structures such as textile antennas – and this is demonstrated with a 0.8GHz to 1.4GHz frequency reconfigurable textile antenna realization. The last section of the dissertation introduces a novel surface imaging array realization by utilizing the microfluidically reconfigurable metallized plate as an RF read-out circuit component. Specifically, a 24 element imaging array is designed and validated to operate within 6 – 12 GHz band with subwavelength resonators to demonstrate the possibility of constructing low-cost high-resolution microwave surface imaging arrays by utilizing the microfluidics based reconfiguration techniques. The presented work emphasizes system level implementation of the proposed devices by integrating them with micropump units, controller boards, and investigating their reliability performances under higher power RF excitations.

The master's thesis deals with the design and implementation of a reconfigurable patch antenna. The antenna is fed by a microstrip transmission line. To the microstrip feeder, tuning stubs are connected. Each stub matches the input impedance of the antenna to 50 ? for different operation frequencies. Stubs can be individually connected to the feeder by PIN diodes; operation frequency of the antenna can be switched that way. In the project, the antenna is initially designed for antenna substrate RO3006. Then, the design will be converted to the substrate ARLON AD600 selected for the realization. In the project, modifications of stubs will be proposed to properly connect the PIN diodes. Functionality of the designed antenna will be verified by modeling in Ansoft Designer. The last part will be dealt with implementation of the antenna and the experimental measurement of their properties.

Aujourd’hui l’électronique fait partie intégrante de nos vies. En effet, de plus en plus d’objets intègrent de l’électronique permettant de les connecter, on appelle cela l’internet des objets (IoT). Tous ces dispositifs disposent d’une connectivité sans fil, rendant ainsi indispensable l’intégration d’une ou plusieurs antennes. De plus, l’électronique devant s’adapter à des objets de plus en plus petits et flexibles embarquant de plus en plus de capteurs tout en consommant de moins en moins d’énergie, il est intéressant de se pencher sur l’étude de nouveaux matériaux pour la réalisation d’antennes devant s’adapter à ces nouvelles contraintes. Dans ce cadre, nous nous sommes attachés dans ce travail de recherche, à la conception de structures antennaires à base de métaux liquides à température ambiante dans le but de réaliser des antennes conformables de formes complexes associant l’impression 3D, des antennes reconfigurables et des structures rayonnantes ayant la capacité de capteur. Dans ce manuscrit des prototypes d’antenne comportant ces caractéristiques ont été simulés, réalisés et mesurés. / Today, electronic is an integral part of our lives. Indeed, more and more objects integrate electronics to connect each other, this is the Internet of Things (IoT). All of these wireless devices need one or more antennas. Furthermore, It’s useful to develop new materials to realize new antennas that fit with new constraints: smaller and flexible objects, more and more sensors and less and less consuming.In this context, we have focused this research on antenna structures based on metals which are liquid at room temperature to realize conformable antennas of complex shapes combining 3D printing, reconfigurable antennas and radiant structures with the ability to sensor. In this manuscript, antenna prototypes with these characteristics have been simulated, realized and measured.

This thesis describes development of a miniature reconfigurable antenna and optimization of a dual tuned birdcage coil. The design goals for the miniature reconfigurable antennas are resonance center frequency of 2.44 GHz, bandwidth of 2.4 GHz - 2.48 GHz, size of 0.8 cm x 1.2 cm, radiation efficiency of 70%, pattern correlation coefficient of 0.3 and input impedance of 50 Ω. The main goals to be achieved from the birdcage coil are the better homogeneity and higher signal to noise ratio than the existing coil. The design and optimization of both antenna and birdcage coil were done using simulation software and MATLAB. Wireless communications have progressed rapidly in last decade and communication devices are becoming smaller and smaller. With miniaturization of devices, dimensions of antennas need to be reduced accordingly. In recent years engineers have not only focused on miniaturization but also on the reconfigurability of the antenna. The functionality and performance of an antenna can be greatly improved by a reconfigurable antenna. However, designing such an antenna can be a tricky task. This thesis addresses issues that are faced during design of such miniature reconfigurable antenna. It also describes design and optimization of such an antenna. The modeled and measured results for the miniature reconfigurable antennas were very close except the built antenna requires frequency tuning and better switching technique. Magnetic resonance imaging (MRI) is an imaging modality that provides high quality images. Radio frequency (RF) coils play an important role in MRI. RF coils act like an antenna that transmits RF energy and receives energy as well. The most commonly-used RF coil for volume imaging is the birdcage coil. This thesis describes an optimization of a birdcage coil that is dual tuned for sodium and hydrogen frequencies. The modeled coil has better performance compared to the existing coil.

Yes / In this paper, we present a simple reconfigurable multiband antenna with two PIN diode switches for WiMAX/WLAN applications. The antenna permits reconfigurable switching in up to ten frequency bands between 2.2 GHz and 6 GHz, with relative impedance bandwidths of around 2.5% and 8%. The proposed antenna has been simulated using CST microwave studio software and fabricated on an FR-4 substrate. It is compact, with an area of 50 × 45 mm2, and has a slotted ground substrate. Both measured and simulated return loss characteristics of the optimized antenna show that it satisfies the requirement of 2.4/5.8 GHz WLAN and 3.5 GHz WiMAX antenna applications. Moreover, there is good agreement between the measured and simulated result in terms of radiation pattern and gain. / Engineering and Physical Science Research Council through Grant EP/E022936A.

No description available.

Yes / Reconfigurable antennas play important roles in smart and adaptive systems and are the subject of many research studies. They offer several advantages such as multifunctional capabilities, minimized volume requirements, low front-end processing efforts with no need for a filtering element, good isolation, and sufficient out-ofband rejection; these make them well suited for use in wireless applications such as fourth generation (4G) and fifth generation (5G) mobile terminals. With the use of active materials such as microelectromechanical systems (MEMS), varactor or p-i-n (PIN) diodes, an antenna’s characteristics can be changed through altering the current flow on the antenna structure. If an antenna is to be reconfigurable into many different states, it needs to have an adequate number of active elements. However, a large number of high-quality active elements increases cost, and necessitates complex biasing networks and control circuitry. We review some recently proposed reconfigurable antenna designs suitable for use in wireless communications such as cognitiveratio (CR), multiple-input multiple-output (MIMO), ultra-wideband (UWB), and 4G/5G mobile terminals. Several examples of antennas with different reconfigurability functions are analyzed and their performances are compared. Characteristics and fundamental properties of reconfigurable antennas with single and multiple reconfigurability modes are investigated. / European Union’s Horizon 2020 research and innovation programme under grant agreement H2020-MSCA-ITN-2016 SECRET-722424.

Yes / This work presents a combination of a cup-shaped monopole antenna and an E-shaped Multi-Mode Resonator (MMR) with the presence of a pair of PIN diodes and a varactor diode to form a compact reconfigurable communication filtering antenna for interweave Cognitive Radio (CR) systems. The proposed filtering antenna operates in the WiMAX band, and it is fabricated on an FR4 substrate with overall dimensions normalized to the wavelength ( λ o ) of the first resonant frequency (0.413λ o × 0.516λ o × 0.0165λ o ). The step and continuous tuning serve the secondary user of the WiMAX CR system to communicate in the absence of the primary users at modifiable resonant frequencies and data rates.When the PIN diodes are OFF, the filtering antenna operates with a fixed odd mode resonant frequency and tunable even mode resonant frequency. This state results in a tunable antenna bandwidth covering a maximum measured frequency range of 3.25-4.02~ GHz and a minimum measured range equal to 3.25-3.58~ GHz. The ON state of the PIN diodes eliminates the antenna matching at the even mode resonant frequency while keeping a strong matching at the odd mode resonant frequency. The resulted operational measured frequency range of the antenna in this state is fixed at 2.9-3.28~ GHz. The filtering antenna has acceptable gain values at the pass band of the E-shaped MMR with a maximum simulated gain value equal to 2.5~ dB and a measured maximum gain equal to 2.48~ dB. The simulated and measured power patterns of the antenna for all diodes states are omnidirectional, which are convenient for portable CR gadgets. / This work was supported in part by the Innovation Programme under Grant H2020-MSCA-ITN-2016 SECRET-722424, and in part by the U.K. Engineering and Physical Sciences Research Council (EPSRC) under Grant EP/E022936/1.

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