Reconfigurable antennas represent a recent innovation in antenna design that changes from classical fixed-form, fixed-function antennas to modifiable structures that can be adapted to fit the requirements of a time varying system. Advances in microwave semiconductor processing technologies have enabled the use of compact, ultra-high quality RF and microwave switches in novel aspects of antenna design. This dissertation introduces the concept of reconfigurable antenna bandwidth control and how advances in switch technology have made these designs realizable. Specifically, it details the development of three new antennas capable of reconfigurable bandwidth control. The newly developed antennas include the reconfigurable ring patch, the reconfigurable planar inverted-F and the reconfigurable parasitic folded dipole. The relevant background work to these designs is described and then design details along with computer simulations and measured experimental results are given. / Ph. D.

This thesis work builds on the concept of reconfiguring the antenna properties (frequency, polarization, radiation pattern) using Radio Frequency (RF) Micro Electro Mechanical Systems (MEMS). This is a part of the overall research performed at the RF Micro/Nano Electro Mechanical Systems (uNeMS) Laboratory at Utah State University, which includes design, microfabrication, test, and characterization of uNeMS integrated cognitive wireless communication systems (Appendix A). In the first step, a compact and broadband Planar Inverted F Antenna (PIFA) is designed with a goal to accommodate reconfigurability at a later stage. Then, a Frequency Reconfigurable Antenna (FRA) is designed using MEMS switches to switch between the Public Safety (PS) bands, 152-162 MHz and 406-512 MHz, while maintaining the integrity of radiation pattern for each band. Finally, robust mechanical designs of the RF MEMS switches accompanied by different analyses have been performed. These analyses are instrumental in obtaining high yield, reliable, robust microfabrication processes including thin film metal deposition and patterning.

Transmitarrays have been shown to be viable architectures for achieving high-directivity reconfigurable apertures. The existing work on reconfigurable transmitarrays is sparse, with only a few experimental demonstrations of reconfigurable implementations. Furthermore, of the designs that have been presented, different approaches have been proposed, but the advantages and drawbacks of these approaches have not been compared. Therefore, in this thesis we present a systematic study of the different approaches to designing reconfigurable transmitarrays, and present designs following these approaches with experimental validation. First, we investigate the distributed-scatterer approach, which is modeled with layers of identical scattering surfaces. We characterize the beamforming capabilities and then present a Method of Moments technique for analyzing and optimizing designs that follow this approach. Then, we present experimental results for a unit cell with varactor-loaded dipoles following this approach. From these results, we demonstrate that the structure thickness following this approach is problematic for beamforming applications. Taking the coupled-resonator approach, we next present a slot-coupled patch design that is significantly thinner and easier to fabricate than designs that follow the first approach. Implementing this design in a fully reconfigurable transmitarray, we demonstrate two-dimensional beamforming. An advantage of this design is that it can also operate as a reflectarray. Next, following the guided-wave approach, we present a transmitarray design that uses a bridged-T phase shifter and proximity-coupled differentially-fed stacked patches. Not only does this design not require vias, it is has a large fractional bandwidth of 10 percent, which is unprecedented in reconfigurable transmitarrays. Implementing this design in a full transmitarray, we experimentally demonstrate reconfigurable two-dimensional beamsteering, as well as shaped-beam synthesis. The main contributions of this thesis are two-fold. First, we thoroughly and systematically compare the transmitarray approaches, which has not been previously done in literature. Secondly, we experimentally demonstrate a reconfigurable array design that achieves better bandwidth, scan angle range, and beam-shaping capability, than existing designs, with reduced fabrication complexity and physical profile.

Transmitarrays have been shown to be viable architectures for achieving high-directivity reconfigurable apertures. The existing work on reconfigurable transmitarrays is sparse, with only a few experimental demonstrations of reconfigurable implementations. Furthermore, of the designs that have been presented, different approaches have been proposed, but the advantages and drawbacks of these approaches have not been compared. Therefore, in this thesis we present a systematic study of the different approaches to designing reconfigurable transmitarrays, and present designs following these approaches with experimental validation. First, we investigate the distributed-scatterer approach, which is modeled with layers of identical scattering surfaces. We characterize the beamforming capabilities and then present a Method of Moments technique for analyzing and optimizing designs that follow this approach. Then, we present experimental results for a unit cell with varactor-loaded dipoles following this approach. From these results, we demonstrate that the structure thickness following this approach is problematic for beamforming applications. Taking the coupled-resonator approach, we next present a slot-coupled patch design that is significantly thinner and easier to fabricate than designs that follow the first approach. Implementing this design in a fully reconfigurable transmitarray, we demonstrate two-dimensional beamforming. An advantage of this design is that it can also operate as a reflectarray. Next, following the guided-wave approach, we present a transmitarray design that uses a bridged-T phase shifter and proximity-coupled differentially-fed stacked patches. Not only does this design not require vias, it is has a large fractional bandwidth of 10 percent, which is unprecedented in reconfigurable transmitarrays. Implementing this design in a full transmitarray, we experimentally demonstrate reconfigurable two-dimensional beamsteering, as well as shaped-beam synthesis. The main contributions of this thesis are two-fold. First, we thoroughly and systematically compare the transmitarray approaches, which has not been previously done in literature. Secondly, we experimentally demonstrate a reconfigurable array design that achieves better bandwidth, scan angle range, and beam-shaping capability, than existing designs, with reduced fabrication complexity and physical profile.

De nos jours, les communications sans fil sont devenues un moyen incontournable et universel d'échange d'un large éventail d'informations entre différents systèmes, certains d'entre eux étant en mouvement comme des drones parmi tant d'autres. Dans le contexte de cette thèse nous considérons une liaison entre un projectile et une station de base. La géométrie de la structure ainsi que les contraintes aérodynamiques d'un tir balistique impliquent l'utilisation d'antennes patchs dans la partie conique à l'avant du projectile. Ce type d'antenne est facile à intégrer à une plate-forme en tant que réseau conformé tout en respectant les contraintes d'encombrement. Ces communications doivent être fiables et discrètes dans un environnement perturbé ou hostile. Les diagrammes de rayonnement du réseau d'antennes doivent présenter des caractéristiques spécifiques, notamment dans le cas particulier d'objets volants et possédant une rotation en roulis (rotation autour de son axe) qui impliquent l'utilisation d'un réseau phasé et commuté par rapport à sa position. Une antenne qui présenterait un rayonnement fixe assurerait une liaison avec un interlocuteur, mais rayonnerait également dans d'autres directions sensibles ce qui pourraient interférer avec la communication principale. La solution qui consiste à activer et désactiver des sous-réseaux verticaux afin d'orienter le lobe principal dans la plan orthogonal à la pointe semble être en accord avec les contraintes de la structure tournante. Un réseau conique a été étudié puis 2 prototypes ont été fabriqués, dont un à l'ISL. Les sous-réseaux sont répartis de manière égale autour de la pointe de façon à pouvoir rayonner dans toutes les directions. De plus, chaque sous-réseau est composé de trois éléments ce qui permet d'orienter également le lobe principal dans le plan longitudinal de la pointe (le long de l'axe du projectile) grâce à un dépointage électronique. Un système électronique de formation de faisceaux a été développé dans le but de contrôler 12 éléments rayonnants. Le réseau d'antennes ainsi que le circuit de répartition ont été caractérisés dans un premier temps de manière indépendante afin d'optimiser les lois de phase nécessaires à dépointer le lobe à partir des pondérations mesurées. Au final, le réseau de 12 éléments associé à son système d'alimentation dédié a été mesuré dans les chambres anéchoïques de DGA-MI et de l'ISL et les mesures sont en accord avec les simulations. / Nowadays wireless communications have become a useful and universal mean to exchange a wide range of information between different systems, some of them being moving, as UAVs among others. In this context we consider here the link between a projectile and a base station. The shape of the structure and the aerodynamic constraints involve the use of patch antennas in the conical front part. This class of antenna is easy to be integrated into the platform as a conformal array, while respecting space constraint. Communications have to be reliable and discrete in disturbed or hostile environment. Antennas array radiation patterns must have some specific characteristics, in particular in the case of flying objects with spin which involves the use of a switched phased array considering its roll position. A fixed-radiation pattern antenna may presents a relevant level or gain toward the interlocutor, but also toward sensitive directions, in which may be located others systems, interfering with the current communication. The solution to switch on and off vertical sub-arrays to steer the beam in the azimuthal plane seem convenient ant fitting the requirements of rotating platform. A conical phased array was studied and two prototypes were manufactured, one at ISL. Sub-arrays are distributed around the conical shape in order to be able to radiate in each direction. Moreover, each sub-array are composed of three radiating elements allowing to steer the main antenna beam in many direction (along the projectile fuze axes). A beam forming network was developed to control the 12 radiating elements conical array. The antenna array and the feeding network were characterized independently in order to optimized the phase of each radiating element. Finally, measurements were done on the whole system in the DGA-MI and ISL anechoic chambers and are in good agreement with simulation results.

The main goal of this research is to develop algorithms to facilitate the use of a new type of antenna, called multifunctional reconfigurable antenna (MRA). Traditional antennas have fixed radiation properties which cannot be changed to adapt to different environments. To solve this problem, MRAs, which can dynamically change its operation frequency, radiation patter, and polarization, has gained a significant interest recently. Such antennas can support multiple radio access technologies with different sets of operational requirements. Reconfigurable antennas are considered smart antennas. The efficient use of smart antennas requires efficient and smart underlying algorithms. This dissertation focuses on developing efficient algorithms to exploit the reconfigurability of MRAs to tap on the superior performances offered by additional degrees of freedom compared to legacy antenna systems.

no / Reconfigurable beam steering using circular disc microstrip patch antenna with a ring slotis proposed. The overall dimension of the antenna is 5.4×5.4 mm2 printed on a 0.504 mm thick, Rogers RT5870 substrate with relative permittivity 2.3 and loss tangent 0.0012. The designed antenna operates at the expected 5G frequency band 60 GHz with a central coaxial probe feed. TwoNMOS switches are configured to generate three different beam patterns. Activating each switch individually results in a near 70 degree shift in the main beam direction, whereas the frequency characteristics are unchanged. The power gains are between 3.9 dB and 4.8dB for the three states of switches configurations. Simulated results in terms of return loss, peak gains and radiation pattern are presented and show a reasonable agreement at the expected 60 GHz bandfor 5G applications. / The published journal webpage is no longer available.

Yes / This paper presented a new circular polarization reconfigurable antenna for 5G wireless communications. The antenna, containing a semicircular slot, was compact in size and had a good axial ratio and frequency response. Two PIN diode switches controlled the reconfiguration for both the right-hand and left-hand circular polarization. Reconfigurable orthogonal polarizations were achieved by changing the states of the two PIN diode switches, and the reflection coefficient |S11| was maintained, which is a strong benefit of this design. The proposed polarization-reconfigurable antenna was modeled using the Computer Simulation Technology (CST) software. It had a 3.4 GHz resonance frequency in both states of reconfiguration, with a good axial ratio below 1.8 dB, and good gain of 4.8 dBic for both modes of operation. The proposed microstrip antenna was fabricated on an FR-4 substrate with a loss tangent of 0.02, and relative dielectric constant of 4.3. The radiating layer had a maximum size of 18.3 18.3 mm2, with 50 W coaxial probe feeding. / European Union’s Horizon 2020 research and innovation programme under grant agreement H2020-MSCA-ITN-2016 SECRET-722424.

Research on multiple antenna systems has been a hot topic in recent years due to the demands for higher transmission rate and more reliable link in rich scattering environment in wireless communications. Using multiple antennas at both the transmitter side and the receiver side increases the channel capacity without additional frequency spectrum and transmitted power. However, due to the limited space at the size-limited terminal devices, the most critical problem in designing multiple antennas is the severe mutual coupling among them. The aim of this thesis is to provide compact, decoupled and efficient multiple antenna designs for terminal devices. At the same time, we propose a simple and cost effective method in multiple antenna measurement. All these efforts contribute to the development of terminal devices for the fourth generation wireless communication. The background and theory of multiple antenna systems are introduced first, in which three operating schemes of multiple antenna systems are discussed. Critical factors influencing the performance of multiple antenna systems are also analyzed in details. To design efficient multiple antenna systems in compact terminals, several decoupling methods, including defected ground plane, current localization, orthogonal polarization and decoupling networks, are proposed. The working mechanism and design procedure of each method are introduced, and their effectiveness is compared. Those methods can be applied to most of the terminal antennas, reducing the mutual coupling by at least 6dB. In some special cases, especially for low frequency bands below 1GHz, the chassis of the device itself radiates like an antenna, which complicates the antenna decoupling. Thus, we extend the general decoupling methods to the cases when the chassis is excited. Based on the characteristic mode analysis, three different solutions are provided, i.e., optimizing antenna locations, localizing antenna currents and creating orthogonal modes. These methods are applied to mobile phones, providing a more reliable link and a higher transmission rate, which are evaluated by diversity gain and channel capacity, respectively. In order to measure the performance of multiple antenna systems, it is necessary to obtain the correlation coefficients. However, the traditional measurement technique, which requires the phase and polarization information of the radiation patterns, is very expensive and time consuming. In this thesis, a more practical and convenient method is proposed. Fairly good accuracy is achieved when it is applied to various kinds of antennas. To design a compact and efficient multiple antenna system, besides the reduction of mutual coupling, the performance of each single antenna is also important. The techniques for antenna reconfiguration are demonstrated. Frequency and pattern reconfigurable antennas are constructed, providing more flexibility to multiple antenna systems. / QC 20120604

Recently, reconfigurable antennas have attracted significant interest due to their high adaptation with changing system requirements and environmental conditions. Reconfigurable antennas have the ability to change their radiation pattern, frequency or polarization independently according to the application requirements. In this thesis, three different reconfigurable antenna structures have been designed / beam-steerable meanderline antenna, dual circularly polarized meanderline antenna and dual-frequency slot-dipole array. Traveling wave meanderline antenna arrays are investigated in detail and a beam-steerable traveling wave meanderline antenna array has been introduced for X-band applications. Beam-steering capability of the antenna array has been achieved by loading the antenna elements with varactor diodes. Theoretical analysis and computer simulations of the proposed antenna have been verified with experimental results. Radiation direction of the 8-element meanderline array can be rotated 10&deg / by changing the varactor diode&rsquo / s bias voltage from 0V up to 20V. Also, a polarization-agile meanderline antenna array has been designed and simulated. Polarization of the circularly polarized meanderline array can be altered between right hand circularly polarized and left hand circularly polarized by using RF MEMS switches. The third type of reconfigurable antenna investigated in this thesis is a dual frequency slot-dipole array operating at X- and Ka-band. Electrical length of the slot dipoles has been tuned by using RF MEMS switches. Antenna prototypes have been manufactured for &lsquo / on&rsquo / and &lsquo / off&rsquo / states of RF MEMS switches and it has been shown that the operating frequency can be changed between 10 GHz and 15.4 GHz.