Origami Reconfigurable Electromagnetic Systems

With the ever-increasing demand for wireless communications, there is a great need for efficient designs of electromagnetic systems. Reconfigurable electromagnetic systems are very useful because such designs can provide multi-functionality and support different services. The geometrical topology of an electromagnetic element is very important as it determines the element’s RF performance characteristics. Origami geometries have significant advantages for launch-and-carry electromagnetic devices where devices need to fold in order to miniaturize their size during launch and unfold in order to operate after the platform has reached orbit. This dissertation demonstrates a practical process for designing reconfigurable electromagnetic devices using origami structures. Four different origami structures are studied and the integrated Mathematical-Computational-Electromagnetic models of origami antennas, origami reflectors and origami antenna arrays are developed and analyzed. These devices provide many unique capabilities compared with the traditional designs, such as band-switching, frequency tuning, polarization adjustment and mode reconfigurability. Prototypes are also manufactured to validate the performances of the designs. These designs change their geometry naturally, and they can be compactly packaged into small volume, which make them very suitable for spaceborne and satellite communication. Origami antennas and origami electromagnetics are expected to impact a variety of applications related to communications, surveillance and sensing

Recent developments and state of the art in flexible and conformal reconfigurable antennas

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. Reconfigurable antennas have gained tremendous interest owing to their multifunctional capabilities while adhering to minimalistic space requirements in ever-shrinking electronics platforms and devices. A stark increase in demand for flexible and conformal antennas in modern and emerging unobtrusive and space-limited electronic systems has led to the development of the flexible and conformal reconfigurable antennas era. Flexible and conformal antennas rely on non-conventional materials and realization approaches, and thus, despite the mature knowledge available for rigid reconfigurable antennas, conventional reconfigurable techniques are not translated to a flexible domain in a straight forward manner. There are notable challenges associated with integration of reconfiguration elements such as switches, mechanical stability of the overall reconfigurable antenna, and the electronic robustness of the resulting devices when exposed to folding of sustained bending operations. This paper reviews various approaches demonstrated thus far, to realize flexible reconfigurable antennas, categorizing them on the basis of reconfiguration attributes, i.e., frequency, pattern, polarization, or a combination of these characteristics. The challenges associated with development and characterization of flexible and conformal reconfigurable antennas, the strengths and limitations of available methods are reviewed considering the progress in recent years, and open challenges for the future research are identified

Reconfigurable Antennas

In this new book, we present a collection of the advanced developments in reconfigurable antennas and metasurfaces. It begins with a review of reconfigurability technologies, and proceeds to the presentation of a series of reconfigurable antennas, UWB MIMO antennas and reconfigurable arrays. Then, reconfigurable metasurfaces are introduced and the latest advances are presented and discussed

Reconfigurable Surfaces Employing Linear-Rotational and Bistable-Translational (LRBT) Joints

Reconfigurable surfaces are useful in many applications. This paper proposes a type of reconfigurable surfaces that consist of rigid elements (tiles) connected by novel compliant joints. Depending on the actuation, these novel connecting joints can either operate as torsional hinges, which create isometric transformation (like origami folding) between connected tiles, or bistable translational springs, which accommodate metric-changing transformation between connected tiles. A specific example of a reconfigurable surface with square tile shape that can morph into flat, cylindrical (in two different directions), and spherical configurations with simple actuation is given

Reconfigurable Surfaces Employing Linear-Rotational and Bistable-Translational (LRBT) Joints

Reconfigurable surfaces are useful in many applications. This paper proposes a type of reconfigurable surfaces that consist of rigid elements (tiles) connected by novel compliant joints. Depending on the actuation, these novel connecting joints can either operate as torsional hinges, which create isometric transformation (like origami folding) between connected tiles, or bistable translational springs, which accommodate metric-changing transformation between connected tiles. A specific example of a reconfigurable surface with square tile shape that can morph into flat, cylindrical (in two different directions), and spherical configurations with simple actuation is given

Applications of Origami Folding Techniques on Antenna Structures using Flexible Substrates

This thesis investigates the use of Origami folding techniques in antenna structures. This application would be suitable for space satellites and military secure communications. The main research is divided into three segments. The first one presents a Vivaldi antenna using flexible substrates, Kapton and Mylar. They are simulated in Computer Simulation Technology (CST) Studio and tested with a Vector Network Analyser (VNA) in the anechoic chamber. The reason for using various flexible substrates is to determine which substrate would perform better when folded. Each substrate has unique electrical and mechanical properties. Secondly, a more specfic Origami folding pattern called Miura Ori is introduced. It is integrated into two antenna designs: Slot antenna and Substrate Integrated Waveguide (SIW) antenna. The Miura Ori folding technique is a repeated pattern with some interesting mechanical properties. It would be able to switch between different states: at, partially folded or fully folded. This would be beneficial for applications where the cost, size and weight are limited. Both antenna designs are simulated and optimised to achieve a good performance, before incorporating the Miura Ori folding technique. There are special parameters that require the model to be functional, Inner angle and Folding angle. Each antenna is simulated by varying those two parameters, because of that the resonant frequency, reflection coefficient (S11), gain and the direction of the radiating angle is changed. Lastly, a microwave switch with nanowires is investigated to provide a fast switching network at each individual antenna. The microwave switch is simulated on a flexible substrate

Expanding the scope of single-molecule energy transfer with gold nanoparticles and graphene

Förster resonance energy transfer (FRET) is a common tool to measure the distances between a donor and an acceptor fluorophore and is employed as a spectroscopic ruler. This non-radiative energy transfer is utilized to not only measure distances but also to observe dynamics in the field of biophysics and medicine. However, main limitations of FRET are the limited time resolution and working range between donor and acceptor molecules of 10 nm. To increase the application of FRET, this limitation can be circumvented by the introduction of different ma-terials in the close proximity. For characterization of the altered distance dependence, a precise distance control between the dyes and the applied material is required, which here is provided by the DNA origami technique. In DNA origami, DNA self-assembles into programmable, complex, and robust structures, which can be easily modified with dyes and other entities with nanometric control. DNA origami nanoantennas constructed of a pair of gold nanoparticles have recently been introduced to substantially increase the obtainable fluorescence signal that yields a higher time resolution in biophysical single-molecule FRET experiments. In this context, it is crucial to understand the influence of the gold nanoparticles on the FRET process itself. In this work, gold nanoparticles are placed next to FRET pairs using the DNA origami technique (see publication I). A measurement procedure to accurately determine energy transfer efficiencies is estab-lished and reveals that in the intermediate coupling regime, the energy transfer efficiency drops in the presence of nanoparticles whereas the energy transfer rate constant from the donor to the acceptor is not significantly altered. Next, graphene is introduced to increase the range of energy transfer. Graphene is a 2D carbon lattice, which can also be employed as an unbleachable broadband acceptor without labeling. To understand the principles of the energy transfer between a fluorophore and the graphene surface, the distance dependence of the energy transfer from a fluorophore to graphene is investigated (see publication II). As such experiments require high quality graphene surfac-es, a cleaning and transferring procedure to generate reproducible graphene-on-glass-coverslips is established (see publication III) and characterized by different spectroscopic methods. Finally, the full potential of graphene-on-glass coverslips as microscopy platforms are highlighted by adopting graphene in the fields of biosensing, biophysics and super-resolution microscopy (see publication IV). The designed biosensors are capable to detect a DNA target, a viscosity change, or the binding of a biomolecule. In addition, FRET between two dyes is expanded by additional graphene energy transfer (GET) that reveals the relative orientation of the FRET pairs to the graphene surface. Finally, GET is used in super-resolution experiments to reach isotopic nanometric 3D-resolution and track a single fluorophore that undergoes 6-nm jumps. The developed techniques and assays have the potential to become the basis for numerous new applications in single-molecule sensing, biophysics, and super-resolution microscopy

Неуниформне хеликоидалне антене

The objective of this thesis is to systematically analyze and optimize nonuniformly-wound helical antennas, along with classical (uniform) helical antennas. The optimization of the nonuniform helical antennas has many degrees of freedom. Hence, the optimization space is large and the optimization task is challenging. It is shown that, in most practical cases, the optimal nonuniform helical antennas outperform the uniform helical antennas presented in the literature. It is also shown that the nonuniform helical antennas are the preferable choice when the losses are low or medium, whereas for high losses, the uniform helical antennas should be used. A large database is assembled from the optimization results, wherefrom a complete design procedure is developed for the nonuniform helical antennas. This procedure comprises all necessary equations and graphs for evaluating the optimal antenna parameters and estimating the antenna characteristics. The design procedure is verified experimentally, by measurements of a fabricated prototype. Quad (2 x 2) arrays of nonuniform helical antennas are also investigated. Their design procedure includes the optimization of single antennas along with their positions in the array. The solution of a real engineering problem is presented: a quad array that meets predefined specifications is designed and a prototype is fabricated and measured.Циљ ове тезе је систематична анализа и оптимизација неуниформно мотаних хеликоидалних антена, као и класичних (униформних) хеликоидалних антена. Оптимизација неуниформних хеликоидалних антена има много степени слободе. Стога је оптимизациони простор велики, а оптимизација изазован задатак. Показано је да, у највећем броју практичних случајева, оптималне неуниформне хеликоидалне антене надмашују по перформансама униформне хеликоидалне антене представљене у литератури. Осим тога, показано је да су неуниформне хеликоидалне антене бољи избор када су губици мали или средњи, док би у случају великих губитака требало користити униформне хеликоидалне антене. Резултати оптимизације чине велику базу података, на основу које је развијен поступак пројектовања неуниформних хеликоидалних антена. Овај поступак обухвата све потребне једначине и графике за одређивање оптималних параметара антена и процену карактеристика антена. Поступак дизајна је потврђен експериментално, мерењем карактеристика реализованог прототипа. Такође су испитивани низови од 2 x 2 неуниформне хеликоидалне антене. Процедура за њихов дизајн садржи оптимизацију засебних антена, као и оптимизацију положаја антена у низу. Представљено је и решење реалног инжењерског проблема: дизајниран је низ од 2 x 2 антене који испуњава унапред дефинисане спецификације, а прототип је направљен и измерен