Reconfigurable microstrip antennas with tunable radiation pattern characteristics

Reconfigurable beam antenna systems are capable of changing their radiation characteristics in real time, such as beam direction, beam shape, beamwidth, etc. Such antenna system is desired for various wireless applications because of many reasons among them; it helps to enhance signal strength received from an intended target, mitigates interference, and accommodates sudden changes in traffic demand of wireless networks. It might also help to reduce the deployment cost of wireless networks infrastructures. In this dissertation, designs for reconfigurable beam microstrip antennas with tunable radiation characteristics have been proposed. The method to achieve these designs is the reconfigurable parasitic element (s) of tunable electrical size, placed in close proximity to the driven patch. A tuning mechanism with the aid of Varactor diodes is introduced for the parasitic patch that effectively allows for controlling its electrical size. This (these) reconfigurable parasitic patch (es) is (are) then applied in different fashions to devise several antenna designs with dynamic electronic control over certain radiation specifications. The accomplished antenna designs in the dissertation are: * Circularly polarized (CP) beam scanning antenna, where two elements microstrip Yagi-Uda antenna is used. The first element is a square patch driven with two probe feeds of quadrature phase for CP excitation. The second element is a parasitic square patch with narrow square-shaped slot carved on its surface. The parasitic patch is adjacent to the driven patch with a small separation distance. Four varactor diodes are placed on the middle of each side of the square slot to facilitate tuning of its electrical size. The parasitic patch electrical size is alloto be effectively tuned by varying the applied reverse biasing DC voltage to the varactors (capacitance value). The CP beam direction is scanned from -36° to 32° with gain variation from 5.7 to 8.2 dBic, and efficiency from 54% to 75.58% along the scanning range. * Two-dimensional beam scanning antenna, where two orthogonal crossed Yagi-Uda antenna configuration is utilized. The driven element is a square patch excited with a probe coaxial feed. The other two parasitic patches are closely placed along the E & H planes of the driven patch. Each parasitic patch has a narrow rectangular slit at its center, where a varactor diode is placed to allow for tuning its electrical size. The beam direction is permitted to be scanned in both the elevation and azimuth planes. The achieved scan range in the elevation plane is from 0° to 32°, whereas in azimuth plan is from 0° to 90°. Along the scanning range, the attained gain changes from 8.1 to 8.9 dBi, and efficiency changes from 86% to 93%. * Tunable beamwidth antenna, with a dynamic control over the radiation beam focusing is proposed. The antenna consists of a square patch excited by a coaxial probe feed, and other two square parasitic patches placed on both sides of the driven along its H-plane. Each parasitic patch has a narrow slit at its center loaded with lumped varactor diode to tune its electrical size. Upon changing the parasitic patches size, the antenna effective aperture is altered, and hence the beamwidth in the H-plane is controlled. The achieved beamwidth tuning range is from 52° to 108°, whereas the gain changes from 6.5 to 8.1 dBi. Throughout the dissertation, 2.45 GHz is chosen, as an example, to be the target frequency. All the designs are validated through experimental measurements for fabricated prototypes, and good agreement is observed between the predicted and measured results

A Wideband Reconfigurable Antenna with 360° Beam Steering for 802.11ac WLAN Applications

© 1963-2012 IEEE. A novel 360° beam steering patch antenna with parasitic elements is presented in this paper. The designed antenna consists of a radiating patch and six parasitic elements, each of which is connected through a group of shorting vias controlled by p-i-n diode switches. By switching on the desired groups of the shorting vias, the electric field distribution inside substrate cavity appears at the desired beam direction. Rotationally switching on the groups of the shorting vias, the performance of 360° beam scanning is realized. To further understand operating mechanism, the antenna is modeled with equivalent circuit in terms of the on and off status of a sector of the antenna, which can be used as a design guide for shorting-vias-controlled reconfigurable microstrip patch antennas. The fabricated antenna achieves a bandwidth of 14.5%, a peak gain of 10 dBi, and the efficiency of 80.5%. The achieved beamwidths are 42° and 97° in azimuth and elevation planes, respectively. With an ability of being steered around zenith axis at six directions, the scanned beam range covers the entire 360°. The physical dimension is only 2.5 λg for the size and 0.5λg for the profile. This antenna operates from 5.1 to 5.9 GHz and has significant meaning in the IEEE 802.11ac wireless local area network applications due to its capabilities of generating 360° steered beams

Q-Band Millimeter-Wave Antennas: An Enabling Technology for MultiGigabit Wireless Backhaul

[EN] The bandwidth demands in mobile communication systems are growing exponentially day by day as the number of users has increased drastically over the last five years. This mobile data explosion, together with the fixed service limitations, requires a new approach to support this increase in bandwidth demand. Solutions based on lower-frequency microwave wireless systems may be able to meet the bandwidth demand in a short term. However, with the small-cell mass deployment requiring total capacities of 1 Gb/s/km2, scalable, multigigabit backhaul systems are required. Millimeter-wave technology fits nicely into these new backhaul scenarios as it provides extended bandwidth for high-capacity links and adaptive throughput rate, which allows efficient and flexible deployment. Besides these advantages, millimeter-wave solutions become even more attractive when the cost of backhaul solutions and the cost of spectrum licenses are factored in. Compared to the cost of laying fiber to a cell base station, which is the only other scalable solution, the millimeter-wave solution becomes the most appropriate approach.The research leading to these results received funding from the European Commission's seventh Framework Programme under grant agreement 288267.Vilar Mateo, R.; Czarny, R.; Lee, ML.; Loiseaux, B.; Sypek, M.; Makowski, M.; Martel, C.... (2014). Q-Band Millimeter-Wave Antennas: An Enabling Technology for MultiGigabit Wireless Backhaul. IEEE Microwave Magazine. 15(4):121-130. https://doi.org/10.1109/MMM.2014.2308769S12113015

Frequency-Reconfigurable Microstrip Patch and Cavity-Backed Slot ESPARs

Wireless communication systems have rapidly evolved over the past decade which has led to an explosion of mobile data traffic. Since more and more wireless devices and sensors are being connected, the transition from the current 4G/LTE mobile network to 5G is expected to happen within the next decade. In order to improve signal-to-noise ratio (SNR), system capacity, and link budget, beam steerable antenna arrays are desirable due to their advantage in spatial selectivity and high directivity. Electronically steerable parasitic array radiator (ESPAR) that can achieve low-cost continuously beamsteering using varactor diodes have attracted a lot of attention. This dissertation explores bandwidth enhancement of the ESPAR using frequency-reconfigurable microstrip patch and cavity-backed slot (CBS) antennas. In chapter 2, an ESPAR of three closely-coupled rectangular patch elements that do not use phase shifters is presented; the beamsteering is realized by tunable reactive loads which are used to control the mutual coupling between the elements. Additional loading varactors are strategically placed on the radiating edge of all the antenna elements to achieve a 15% continuous frequency tuning range while simultaneously preserving the beamsteering capability at each operating frequency. Therefore, this frequency-reconfigurable ESPAR is able to provide spectrum diversity in addition to the spatial diversity inherent in a frequency-fixed ESPAR. A prototype of the patch ESPAR is fabricated and demonstrated to operate from 0.87 to 1.02 GHz with an instantaneous fractional bandwidth (FBW) of ~1%. At each operating frequency, this ESPAR is able to scan from -20 to +20 degrees in the H plane. However, the beamsteering of the patch ESPAR is limited in the H-plane and its instantaneous S11 fractional bandwidth (FBW) is very narrow. This dissertation also explores how to achieve 2-D beamsteering with enhanced FBW using CBS antennas. A 20-element cavity-backed slot antenna array is designed and fabricated based on a CBS ESPAR cross subarray in chapter 5. This ESPAR array is able to steer the main beam from +45 degrees to -45 degrees in the E plane and from +40 degrees to -40 degrees in the H plane, respectively, without grating lobes in either plane. The impedance matching is maintained below -10 dB from 6.0 to 6.4 GHz (6.4% fractional bandwidth) at all scan angles. In addition, the CBS ESPAR exhibits minimum beam squint at all scan angles within the impedance matching bandwidth. This array successfully demonstrates the cost savings and associated reduction in the required number of phase shifters in the RF front end by employing ESPAR technology

Low Power Reconfigurable Antenna with Continuous Beam Steering Capability

Each year, the number of wireless devices increases, and the size of the devices’ data is increases, 8k video streaming, for example. More and more bandwidth is needed for wireless networks to meet these growing demands. Higher frequencies allow for more bandwidth; however, using higher frequencies comes with some trade-offs. The higher the wireless signal frequency, the shorter the distance it can travel before the signal strength becomes too weak for the receiver to pick it up. One solution might be to increase the power of the signal provider, but that would waste a lot of energy. Most antennas radiate in all directions, so a lot of that extra power would be going up to space, or just away from the device it’s trying to connect with, or it could be picked up as noise by a device on a different network. Instead, in many areas of research, including the research presented here, the issue is addressed by creating a better antenna. This research presents an antenna that focuses its radiated energy into a beam towards the target device. Focusing the power towards a device increases the signal’s power going towards that device without much power going in undesired directions. If the target device moves, then the beam needs to be steered, so it keeps pointing at the device. The ability for an antenna to change something like the direction of its beam makes the antenna a reconfigurable antenna. Some reconfigurable antennas only have a few beam directions to choose from, so they would have to pick the closest one to the target device. The beam can be steered smoothly through any horizontal direction between two limits for this research. This research uses less power and fewer components to do so compared with some previous works

A Wideband Reconfigurable Folded Planar Dipole Using MEMS And Hybrid Polymeric Substrates

A wideband reconfigurable folded planar dipole using hybrid polymeric substrates is proposed. Artificial Magnetic Conductor (AMC) is a periodic structure composed of rectangular patches integrated with Jerusalem Cross (JSC) slots and being located in between two substrates. The Perfect Magnetic Conductor (PMC)-like behaviour of the AMC structure enabled the printed folded dipole to be placed near to the proposed structure, resulting in a low-profile antenna with 5.11 dB gain operating at 9.41 GHz. The combined use of the polymeric substrate and the proposed AMC resulted in a 1 GHz of bandwidth. The proposed antenna is capable in beam steering on the xz-plane via the integration of radio frequency (RF) MEMS switches placed on the antenna feeding transmission line. Simulations and measurements show a satisfactory agreement, with a beam steering capability at least 30, bandwidth of 1 GHz and maximum gain of 5.11 dB

ELECTRONICAL LY RECONFIGURABLE FS S - INSPIRED TRANSMITARRAY FOR TWO DIMENS IONAL BEAMSTEERING FOR 5G ANDRADAR APPL ICATIONS AT 2 8 GHZ

In this dissertation, the author’s work on a 28 GHz transmitarray capable of antenna beamsteering for various wireless applications, is presented. Such device allows for the adjustment of the radiation pattern of an antenna by changing its main lobe direction, without the need of any mechanical means. A unit-cell based on a square-slot Frequency Selective Surface (FSS) is designed, simulated and optimised through several full-wave simulations, using an electromagnetic solver (CST MWS). Subsequently, the unit-cell was extended to a 10x10 array configuration in order to enable Two-dimensional (2D) beamsteering. This work yielded the fabrication of a prototype composed of four passive transmitarray lens, which were experimentally tested and characterised. Finally, a novel unit-cell based on a double square-slot intended aiming at active beamsteering was also studied and optimised in simulation environment. From this work, it was demonstrated that transmitarray can be seen as feasible alternative to many traditional beamsteering techniques, such as phased antenna arrays, while reducing the RF burden of the overall system using only a single radiation source. This fact, allied with it’s ease of integration, reduced cost and low-profile characteristics make transmitarrays a desirable solution for 5G and RADAR applications, among others

Reconfigurable pixel antennas for communications

The explosive growth of wireless communications has brought new requirements in terms of compactness, mobility and multi-functionality that pushes antenna research. In this context, recon gurable antennas have gained a lot of attention due to their ability to adjust dynamically their frequency and radiation properties, providing multiple functionalities and being able to adapt themselves to a changing environment. A pixel antenna is a particular type of recon gurable antenna composed of a grid of metallic patches interconnected by RF-switches which can dynamically reshape its active surface. This capability provides pixel antennas with a recon guration level much higher than in other recon gurable architectures. Despite the outstanding recon guration capabilities of pixel antennas, there are important practical issues related to the performance-complexity balance that must be addressed before they can be implemented in commercial systems. This doctoral work focuses on the minimization of the pixel antenna complexity while maximizing its recon guration capabilities, contributing to the development of pixel antennas from a conceptual structure towards a practical recon gurable antenna architecture. First, the conceptualization of novel pixel geometries is addressed. It is shown that antenna complexity can be signi cantly reduced by using multiple-sized pixels. This multi-size technique allows to design pixel antennas with a number of switches one order of magnitude lower than in common pixel structures, while preserving high multiparameter recon gurability. A new conceptual architecture where the pixel surface acts as a parasitic layer is also proposed. The parasitic nature of the pixel layer leads to important advantages regarding the switch biasing and integration possibilities. Secondly, new pixel recon guration technologies are explored. After investigating the capabilities of semiconductors and RF-MEMS switches, micro uidic technology is proposed as a new technology to create and remove liquid metal pixels rather than interconnecting them. Thirdly, the full multi-parameter recon guration capabilities of pixel antennas is explored, which contrasts with the partial explorations available in the literature. The maximum achievable recon guration ranges (frequency range, beam-steering angular range and polarization modes) as well as the linkage between the di erent parameter under recon guration are studied. Finally, the performance of recon gurable antennas in beam-steering applications is analyzed. Figures-of-merit are derived to quantify radiation pattern recon gurability, enabling the evaluation of the performance of recon gurable antennas, pixel antennas and recon guration algorithms

Reconfigurable pixel antennas for communications

Premi extraordinari doctorat curs 2012-2013, àmbit Enginyeria de les TICThe explosive growth of wireless communications has brought new requirements in terms of compactness, mobility and multi-functionality that pushes antenna research. In this context, recon gurable antennas have gained a lot of attention due to their ability to adjust dynamically their frequency and radiation properties, providing multiple functionalities and being able to adapt themselves to a changing environment. A pixel antenna is a particular type of recon gurable antenna composed of a grid of metallic patches interconnected by RF-switches which can dynamically reshape its active surface. This capability provides pixel antennas with a recon guration level much higher than in other recon gurable architectures. Despite the outstanding recon guration capabilities of pixel antennas, there are important practical issues related to the performance-complexity balance that must be addressed before they can be implemented in commercial systems. This doctoral work focuses on the minimization of the pixel antenna complexity while maximizing its recon guration capabilities, contributing to the development of pixel antennas from a conceptual structure towards a practical recon gurable antenna architecture. First, the conceptualization of novel pixel geometries is addressed. It is shown that antenna complexity can be signi cantly reduced by using multiple-sized pixels. This multi-size technique allows to design pixel antennas with a number of switches one order of magnitude lower than in common pixel structures, while preserving high multiparameter recon gurability. A new conceptual architecture where the pixel surface acts as a parasitic layer is also proposed. The parasitic nature of the pixel layer leads to important advantages regarding the switch biasing and integration possibilities. Secondly, new pixel recon guration technologies are explored. After investigating the capabilities of semiconductors and RF-MEMS switches, micro uidic technology is proposed as a new technology to create and remove liquid metal pixels rather than interconnecting them. Thirdly, the full multi-parameter recon guration capabilities of pixel antennas is explored, which contrasts with the partial explorations available in the literature. The maximum achievable recon guration ranges (frequency range, beam-steering angular range and polarization modes) as well as the linkage between the di erent parameter under recon guration are studied. Finally, the performance of recon gurable antennas in beam-steering applications is analyzed. Figures-of-merit are derived to quantify radiation pattern recon gurability, enabling the evaluation of the performance of recon gurable antennas, pixel antennas and recon guration algorithms.Award-winningPostprint (published version

Analysis and design of new electronically reconfigurable periodic leaky-wave antennas

[SPA] El principal objetivo de la tesis es el estudio de nuevas tecnologías en el campo de las antenas reconfigurables. En particular, la tesis se centra en explorar y explotar el potencial que presentan un tipo de antenas denominadas como ¿Antenas basadas en Modos de Fuga¿ para controlar electrónicamente su diagrama de radiación. La tesis desarrolla el análisis, diseño y fabricación de tres novedosas antenas basadas en modos de fuga capaces de variar mediante unas pocas señales de control y de forma continua su ángulo de apuntamiento. El mecanismo de reconfiguración electrónica principalmente se basa en el control de la dispersión de los modos de fuga excitados en dichas estructuras, mediante un control electrónico introducido empleando estructuras periódicas resonantes combinadas con elementos activos tales como diodos varactores. La tesis demuestra claramente la utilidad de estas antenas en el campo de la reconfiguración electrónica, proponiendo estas nuevas estructuras como alternativas a otras soluciones más clásicas (como antenas en array de fase reconfigurables o reflectores parabólicos mecánicamente re-orientables mecánicamente) y otras de actualidad (como reflectarrays, transmitarrays, antenas metamateriales o antenas pixeladas), las cuales todas ellas presentan otros problemas en términos de coste, complejidad de diseño o limitaciones de escalabilidad en frecuencia, aportando así esta tesis novedosos conceptos de reconfiguración electrónica.[ENG] The thesis aims the design of novel reconfigurable antennas with electronic beam-scanning. In particular, the antennas analyzed are known as Fabry-Perot Antennas (FPA) and are currently of high interest in the scientific community because of their high-directivity, low-profile and structure simplicity, what allow them to be an interesting alternative to other technologies (e.g. parabolic reflectors, phased arrays, etc.) which require of complex power distribution networks, bulky external sources or costly techniques to achieve reconfigurable capabilities. In this thesis, the integration of active components, such as varactor diodes, with FPRA structures, is exploited to achieve electronic control of their aperture illumination, which in turn results in the electronic steering of the radiation-pattern main beam. A modal analysis based on the leaky-wave theory has allowed to understand and predict the behavior of these structures. An equivalent circuit model was developed to design and optimize the dimensions of theses complex structures, saving computational cost and time. The antennas are based on the control of the frequency dispersion response and the electromagnetic band-gap (EBG) properties of periodic structures, employing specially designed Frequency-Selective Surfaces (FSS) loaded with varactor diodes. Three novel antenna prototypes were manufactured to demonstrate electronic steering capability operating at 5.5GHz. Continuous scanning in elevation (1D scanning) and also in elevation and azimuth simultaneously (2D scanning) have been achieved employing just a few control signals (between 1 and 4 signals). The antenna structures have been implemented in a low-cost technology based on parallel plate waveguides and printed circuit boards which have allowed to design antennas with a reduced profile. Theoretical, simulated and experimental results are shown for each prototype to demonstrate the concepts. Also, some future lines related to novel planar reconfigurable antennas in development are also outlined. One of the main potential advantages of the reconfiguring principles presented for future applications is their frequency scalability. This would allow to apply these concepts to other technologies, such as MEMS or graphene, to build new reconfigurable antennas able to operate at higher frequency bands (e.g. mm-bands) for future applications.Universidad Politécnica de Cartagen