Investigation of MIMO Communications

This project focuses on the background of multiple input multiple output (MIMO) communication and its advantages over the other possible implementations. A background of wireless communication in regards to modulation types, information theory, antenna background and a hardware implementation using a VSA and VSG is provided. The theory is compared and verified with the hardware implementation with regards to the effect of the increase in the number of antennas and the parameter vector error magnitude

Engineering for a changing world: 60th Ilmenau Scientific Colloquium, Technische Universität Ilmenau, September 04-08, 2023 : programme

In 2023, the Ilmenau Scientific Colloquium is once more organised by the Department of Mechanical Engineering. The title of this year’s conference “Engineering for a Changing World” refers to limited natural resources of our planet, to massive changes in cooperation between continents, countries, institutions and people – enabled by the increased implementation of information technology as the probably most dominant driver in many fields. The Colloquium, supplemented by workshops, is characterised but not limited to the following topics: – Precision engineering and measurement technology Nanofabrication – Industry 4.0 and digitalisation in mechanical engineering – Mechatronics, biomechatronics and mechanism technology – Systems engineering – Productive teaming - Human-machine collaboration in the production environment The topics are oriented on key strategic aspects of research and teaching in Mechanical Engineering at our university

1-D broadside-radiating leaky-wave antenna based on a numerically synthesized impedance surface

A newly-developed deterministic numerical technique for the automated design of metasurface antennas is applied here for the first time to the design of a 1-D printed Leaky-Wave Antenna (LWA) for broadside radiation. The surface impedance synthesis process does not require any a priori knowledge on the impedance pattern, and starts from a mask constraint on the desired far-field and practical bounds on the unit cell impedance values. The designed reactance surface for broadside radiation exhibits a non conventional patterning; this highlights the merit of using an automated design process for a design well known to be challenging for analytical methods. The antenna is physically implemented with an array of metal strips with varying gap widths and simulation results show very good agreement with the predicted performance

Beam scanning by liquid-crystal biasing in a modified SIW structure

A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium

HIGH-PERFORMANCE PERIODIC ANTENNAS WITH HIGH ASPECT RATIO VERTICAL FEATURES AND LARGE INTERCELL CAPACITANCES FOR MICROWAVE APPLICATIONS

Modern communications systems are evolving rapidly to address the demand for data exchange, a fact which imposes stringent requirements on the design process of their RF and antenna front-ends. The most crucial pressure on the antenna front-end is the need for miniaturized design solutions while maintaining the desired radiation performance. To satisfy this need, this thesis presents innovative types of periodic antennas, including electromagnetic bandgap (EBG) antennas, which are distinguished in two respects. First, the periodic cells contain thick metal traces, contrary to the conventional thin-trace cells. Second, such thick traces contain very narrow gaps with very tall sidewalls, referred to as high aspect ratio (HAR) gaps. When such cells are used in the structure of the proposed periodic antennas, the high capacitance of HAR gaps decreases the resonance frequency, mitigates conduction loss, and thus, yields considerably small high efficiency antennas. For instance, one of the sample antenna designs with only two EBG cells offers a very small XYZ volume of 0.25λ×0.28λ×0.037λ with efficiency of 83%. Also, a circularly polarized HAR EBG antenna is presented which has a footprint as small as 0.26λ×0.29λ and efficiency as high as 94%. The main analysis method developed in this thesis is a combination of numerical and mathematical analyses and is referred to as HFSS/Bloch method. The numerical part of this method is conducted using a High Frequency Structure Simulator (HFSS), and the mathematical part is based on the classic Bloch theory. The HFSS/Bloch method acts as the mainstay of the thesis and all designs are built upon the insight provided by this method. A circuit model using transmission line (TL) theory is also developed for some of the unit cells and antennas. The HFSS/Bloch perspective results in a HAR EBG TL with radiation properties, a fragment of which (2 to 6 cells) is introduced as a novel antenna, the self-excited EBG resonator antenna (SE-EBG-RA). Open (OC) and short circuited (SC) versions of this antenna are studied and the inherently smaller size of the SC version is demonstrated. Moreover, the possibility of employing the SE-EBG-RA as the element of a series-fed array structure is investigated and some sample high-efficiency, flat array antennas are rendered. A microstrip antenna is also developed, the structure of which is composed of 3×3 unit cells and shows fast-wave behaviors. Most antenna designs are resonant in nature; however, in one case, a low-profile efficient leaky-wave antenna with scanning radiation pattern is proposed. Several antenna prototypes are fabricated and tested to validate the analyses and designs. As the structures are based on tall metal traces, two relevant fabrication methods are considered, including CNC machining and deep X-ray lithography (DXRL). Hands-on experiments provide an outlook of possible future DXRL fabricated SE-EBG-RAs

An investigation of extraocular and intraocular wireless communication techniques on a retinal prosthesis system

Retinitis Pigmentosa (RP) and Age-related Macular Degeneration (AMD) are two genetic ocular diseases that cause gradual visual impairments which will eventually lead to blindness as a result of damage in the retina. In the cases of people suffering from RP and AMD, it has been found out that 95% of the photoreceptors are damaged, while interestingly majority of the bipolar and ganglion cells that are responsible for the nerve stimulation remain intact. This is where a retinal prosthesis system comes into the picture. Retinal prosthesis is a prosthetic device that is aimed to assume the functionality of the damaged photoreceptors and produce stimulations to the bipolar and ganglion cells for a visual perception. Typically, a retinal prosthesis system comprises of two major components: an image capturing unit and an array of microelectrode. While a lot of studies have been conducted on each major component, the development of the wireless link between the two components has been mostly overlooked. It is clear that the two components are not physically connected and a data exchange is required between the two. This thesis aims to bridge the knowledge gap in this area by addressing the following research questions: “What is the most suitable frequency band for a wireless link in a retinal prosthesis system?” and “What kind of antenna would generate the most optimal performance under the constraints introduced by a retinal prosthesis system?

Cavity-Coupled Plasmonic Systems for Enhanced Light-Matter Interactions

Light-matter interaction is a pivotal effect that involves the synergetic interplay of electromag- netic fields with fundamental particles. In this regard localized surface plasmons (LSP) arise from coherent interaction of the electromagnetic field with the collective oscillation of free electrons in confined sub-wavelength environments. Their most attractive properties are strong field en- hancements at the near field, highly inhomogeneous, peculiar temporal and spatial distributions and unique polarization properties. LSP systems also offer a unique playground for fundamental electromagnetic physics where micro-scale systemic properties can be studied in the macro-scale. These important properties and opportunities are brought up in this work where I study hybrid cavity-coupled plasmonic systems in which the weak plasmonic element is far-field coupled with the photonic cavity by properly tuning its phase. In this work I preset the fundamental understand- ing of such a complex systems from the multi-resonance interaction picture along experimental demonstration. Using this platform and its intricate near fields I further demonstrate a novel mech- anism to generate superchiral light: a field polarization property that adds a degree of freedom to light-matter interactions at the nanoscale exploited in advanced sensing applications and surface effect processes. Finally, the detection of non-chiral analytes, such as proteins, neurotransmit- ters or nanoparticles, and more complex chiral analytes, such as proteins and its conformation states, amino acids or chiral molecules at low concentrations is demonstrated in several biosensing applications. The accompanied experiential demonstrations were accomplished using the nanoim- printing technique, which places the cavity-coupled hybrid plasmonic system as a unique platform towards realistic applications not limited by expensive lithographic techniques

Experimental Fabrication and Characterisation of Textile Metamaterial Structures for Microwave Applications

PhDThis thesis presents an investigation of fabrication technologies and electromagnetic characterisation of textile metamaterials in the microwave frequency range. Interdisciplinary in nature, the work bridges textile design practice and electromagnetic engineering. The particular ambition was to explore a number of surface techniques prevalent in the textile design field, and map their suitability for the construction of metatextiles for microwave operation. Two different classes of metatextiles, all-dielectric and dielectric with electrically conductive patterns, were examined. First, five structures of all-dielectric textiles and papers are reported; three textiles with graded embroidered and screen printed patterns, and two papers embellished with regular and irregular laser cut patterns. Permittivities for these materials were measured in a purpose-built test chamber and shown to be similar to permittivity ranges exhibited by solid discrete metamaterial cells previously reported in the scientific literature. Importantly these metatextiles were realised within one textile surface and one fabrication process, bypassing the need to assemble large numbers of isotropic material cells. This reveals the potential for rapid and low-cost manufacture of graded textile materials to produce anisotropic ground plane cloaks. Secondly, three studies are presented that examine the use of electrically conductive patterned textile materials in the design of metatextiles which exhibit negative refractive index over a narrow frequency band. A range of e-textile (electronic textile) fabrication technologies were explored to assess their suitability for prototyping splitring and wire arrays, resonating in a narrow region between 3 - 10 GHz. Designs utilised a repeated unit cell pattern on a two-dimensional textile surface and were subsequently pleated into the required three-dimensional structure. A small negative refractive index was achieved for an embroidered prototype at 4.9 GHz, and two ‘printed and plated’ prototypes at, 7.5 GHz and 9.5 GHz respectively. In summary the thesis demonstrates a set of guidelines for the fabrication of textile metamaterials for microwave frequencies, derived through a practice-led and interdisciplinary method based on material experimentation.Media and Arts Technology programme, EPSRC Doctoral Training Centre EP/G03723X/1

Development of a window system with optimised ventilation and noise-reduction performance: an approach using metamaterials.

Noise transmission is a key factor regarding indoor comfort and energy-smart Architecture and Engineering. In most cases, occupants of the building must choose between a naturally ventilated indoor environment or a quiet one. On the other hand, the acoustic metamaterials (AMMs) allow more customisable physical properties according to their spatial configurations, proving significant merits over traditional architecture and engineering materials. This PhD study will investigate AMMs techniques to develop a window system that can control the incoming noise while allowing natural ventilation. This is a crucial point for AMMs research. So far, even if many solutions have been developed to pursue this objective, they still lack ergonomics and human perception analysis. Through a multi-disciplinary methodology, the author first a) highlighted which are the ergonomic principles that add value to the window system from the users perspective, then b) investigated a series of suitable AMMs techniques to be applied for noise reduction and natural ventilation, c) developed a specific AMM design suitable to follow those ergonomic principles previously highlighted and assessed it through human perception, and finally d) optimised a full-scale prototype for a broad acoustic range and customisable ergonomic application. Social science, ergonomic, numerical, analytical and experimental studies were used throughout the PhD project to draw a full-scale window prototype using AMMs to allow natural ventilation independently from the outdoor noise situation. The so-called acoustic metawindow (AMW) allows Transmission Loss (TL) of 10-80dB on a significant frequency range for human hearing (50-5000Hz) in an open configuration while allowing sufficient natural ventilation. In addition, the AMW is proved to positively impact the indoor environment from both physical and human perception points of view thanks to its ergonomic nature. This project will open a new AMMs field of investigation that is not limited to noise reduction but also includes outdoor stimuli optimisation towards a more comprehensive indoor comfort