A novel material characterization method for magneto-dielectric composite material was proposed. MD materials have been reported as providing new opportunities for effective antenna size reduction in many studies. Since MD materials have to be realized through material synthesis, an accurate measurement method is required to extract them. The proposed method, cavity perturbation technique using substrate integrated waveguide cavity resonator, has been demonstrated through theories, simulations and measurement that it can be used to extract both electric and magnetic properties of the MD composite material effectively. MD materials using cobalt-fluoropolymer have been synthesized and material design guidelines for antenna applications are also provided. The benefits of using MD materials on antenna miniaturization was also demonstrated by comparing the performance of an antenna on MD material to other antennae on high dielectric constant materials and FR-4 material. Through simulations and measurements, the MD material is a promising solution for next generation smartphone or wearable type applications.

abstract: Fingerprints have been widely used as a practical method of biometrics authentication or identification with a significant level of security. However, several spoofing methods have been used in the last few years to bypass fingerprint scanners, thus compromising data security. The most common attacks occur by the use of fake fingerprint during image capturing. Imposters can build a fake fingerprint from a latent fingerprint left on items such as glasses, doorknobs, glossy paper, etc. Current mobile fingerprint scanning technology is incapable of differentiating real from artificial fingers made from gelatin molds and other materials. In this work, the adequacy of terahertz imaging was studied as an alternative fingerprint scanning technique that will enhance biometrics security by identifying superficial skin traits. Terahertz waves (0.1 – 10 THz) are a non-ionizing radiation with significant penetration depth in several non-metallic materials. Several finger skin features, such as valley depth and sweat ducts, can possibly be imaged by employing the necessary imaging topology. As such, two imaging approaches 1) using quasi-optical components and 2) using near-field probing were investigated. The numerical study is accomplished using a commercial Finite Element Method tool (ANSYS, HFSS) and several laboratory experiments are conducted to evaluate the imaging performance of the topologies. The study has shown that terahertz waves can provide high spatial resolution images of the skin undulations (valleys and ridges) and under certain conditions identify the sweat duct pattern. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2017

La transformation d'espace (TE) a été développée par J. B. Pendry et U. Leonhardt en 2006 et suscite un énorme intérêt depuis la démonstration expérimentale de la première cape d'invisibilité en micro-ondes. Cette technique permet de contrôler la propagation des ondes en modifiant les propriétés électromagnétiques de l'espace. Malgré quelques limitations liées à la bande passante ou aux pertes consécutives à l'utilisation de métamatériaux pour les dispositifs TE, cette technique a attiré l'attention de nombreux domaines (optique, microondes, acoustique, etc). L'objectif de cette thèse est de développer des applications de la TE dans le domaine antennaire à l'aide de matériaux conventionnels lorsque cela est possible et aussi d'ouvrir de nouvelles voies dans le contrôle du rayonnement des antennes. Trois applications ont été étudiées: le réflecteur « parabolique plat »; un superstrat tout diélectrique pour contrôler l'ouverture angulaire d'une antenne patch; et finalement un superstrat permettant de modifier drastiquement le rayonnement d'une antenne. Ce travail a été financé par les agences de défense du Royaume Uni et de la France (DSTL et DGA respectivement), dans le cadre du projet MIMiCRA (Metamaterial Inspired Microwave Conformai Radar Antennas). / Transformation Electromagnetics technique was introduced by J. B. Pendry and U. Leonahrdt in 2006 and it has become an emerging research field in physics and engineering in the last few years after the concept was validated experimentally with a invisibility cloak in microwave regime. This technique claims the possibility of an unprecedented technique to control electromagnetic waves interaction with engineered materials to achieve exotic electromagnetic behaviour. Despite some issues about narrow bandwidth or excessive dispersive losses related to the use of metamaterials for realization of TE devices, this technique caught the attention in many research fields (optics microwave, acoustics, etc). The final purpose of this these is to explore and propose applications of Transformation Electromagnetics in the antenna design field by using standard materials with the purpose of controlling the radiation pattern of an antenna. More precisely, three applications were explored : a fiat "parabolic reflector", an all-dielectric superstrate to control the half power beamwidth of a patch antenna and finally a superstrate that allows to control drastically the radiation pattern of a planar antenna This work was funded by France and UK defence agencies (DSTL and DGA respectively), within the framework of MIMiCRA project (Metamateriallnspired Microwave Conformai Radar Antennas).

A linearly-polarized aperture coupled patch antenna design is characterized and optimized using HFSS antenna simulation software. This thesis focuses on the aperture coupled patch antenna due to the lack of fabrication and tuning documentation for the design of this antenna and its usefulness in arrays and orthogonally polarized communications. The goal of this thesis is to explore dimension effects on aperture coupled antenna performance, to develop a design and tuning procedure, and to describe performance effects through electromagnetic principles. Antenna parameters examined in this study include the dimensions and locations of the substrates, feed line, ground plane coupling slot, and patch. The operating frequency, input VSWR, percent bandwidth, polarization ratio, and broadside gain are determined for each antenna configuration. The substrate material is changed from RT Duroid (material in nominal HFSS design) to FR4 due to lower cost and availability. The operating frequency is changed from 2.3GHz (specified in nominal HFSS design) to 2.4GHz for wireless communication applications. Required dimensional adjustments when changing substrate materials and operating frequencies for this antenna are non-trivial and the new design procedure is used to tune the antenna. The antenna is fabricated using 59mil thick double and single sided FR4 boards joined together with double sided 45mil thick acrylic tape. The antenna is characterized in an anechoic chamber and experimental results are compared to theoretical predictions. The results show that the new design procedure can be successfully applied to aperture coupled antenna design.

A non-stationary Krylov subspace based iterative solver for the three dimensional finite element-boundary integral (FE-BI) method for implantable antennas is presented. The present method numerically solves the frequency domain Maxwell?s equations in the variational form to formulate the finite element solution using hexahedral discretization elements in conjunction with the appropriate boundary integral equations. Four different solvers are used to investigate the convergence behavior of the FE-BI technique on the design of the antennas. The scheme is then applied to two miniaturized planar inverted-F antennas (PIFA): a serpentine and a spiral. The antennas are designed for the Medical Implant Communication Service (MICS) band (402-405 MHz). Validations and comparisons are done using High Frequency Electromagnetic Simulation (HFSS) software. Return loss, gain, near fields, and far fields are presented for the serpentine and spiral antenna.

The Radio Neutrino Observatory in Greenland (RNO-G) is a multidisciplinary, multinational collaboration which uses antennas to detect neutrino interactions with arctic ice sheets. Neutrinos are formed from nuclear reactions; predominant sources include nuclear reactors, stars, supernovae, and the big bang. They rarely interact with normal matter and thus travel from origin to destination relatively unimpeded, with applications including tracking nuclear weapons tests and supernovae. Measurements of galactic neutrino flux can provide information about how the universe developed and its current evolution. Neutrino interactions produce signals from 100 to 1000MHz. Current RNO-G antennas operate over only a portion of this band; 200MHz for horizontally polarized (Hpol) and 400MHz for vertically polarized (Vpol). In this thesis, multiple lengths of Hpol antennas are combined, and exponentially tapered geometry is added to the Vpol antenna to improve performance. Both polarizations are combined into one structure to improve observatory performance. This thesis details the design, fabrication, and testing of a new RNO-G antenna iteration. Each design is compared to frequency, gain, matching, and size requirements. Two variations of the final design are fabricated and tested, with performance compared to simulation.

Multiple-Input Multiple-Output (MIMO) systems are a pivotal solution for the significant enhancement of the band-limited wireless channels’ communication capacity. MIMO system is essentially a wireless system with multiple antennas at both the transmitter and receiver ends. Compared to the conventional wireless systems, the main advantages of the MIMO systems are the higher system capacity, more bit rates, more link reliability, and wider coverage area. All of these features are currently considered as crucial performance requirements in wireless communications. Additionally, the emerging new services in wireless applications have created a great motivation to utilize the MIMO systems to fulfil the demands these applications create. The MIMO systems can be combined with other intelligent techniques to achieve these benefits by employing a higher spectral efficiency. The MIMO system design is a multifaceted problem which needs both antenna considerations and baseband signal processing. The performance of the MIMO systems depends on the cross-correlation coefficients between the transmitted/received signals by different antenna elements. Therefore, the Electromagnetic (EM) characteristics of the antenna elements and wireless environment can significantly affect the MIMO system performance. Hence, it is important to include the EM properties of the antenna elements and the physical environment in the MIMO system design and optimizations. In this research, the MIMO system model and system performance are introduced, and the optimum MIMO antenna system is investigated and developed by considering the electromagnetic aspects within three inter-related topics: 1) Fast Numerical Analysis and Optimization of the MIMO Antenna Structures: An efficient and fast optimization method is proposed based on the reciprocity theorem along with the method of moment analysis to minimize the correlation among the received/transmitted signals in MIMO systems. In this method, the effects of the radio package (enclosure) on the MIMO system performance are also included. The proposed optimization method is used in a few practical examples to find the optimal positions and orientations of the antenna elements on the system enclosure in order to minimize the cross-correlation coefficients, leading to an efficient MIMO operation. 2) Analytical Electromagnetic-Theoretic Model for the MIMO Antenna Design: The first requirement for the MIMO antennas is to obtain orthogonal radiation modes in order to achieve uncorrelated signals. Since the Spherical Vector Waves (SVW) form a complete set of orthogonal Eigen-vector functions for the radiated electromagnetic fields, an analytical method based on the SVW approach is developed to excite the orthogonal SVWs to be used as the various orthogonal modes of the MIMO antenna systems. The analytic SVW approach is used to design spherical antennas and to investigate the orthogonality of the radiation modes in the planar antenna structures. 3) Systematic SVW Methodology for the MIMO Antenna Design: Based on the spherical vector waves, a generalized systematic method is proposed for the MIMO antenna design and analysis. The newly developed methodology not only leads to a systematic approach for designing MIMO antennas, but can also be used to determine the fundamental limits and degrees of freedom for designing the optimal antenna elements in terms of the given practical restrictions. The proposed method includes the EM aspects of the antenna elements and the physical environment in the MIMO antenna system, which will provide a general guideline for obtaining the optimal current sources to achieve the orthogonal MIMO modes. The proposed methodology can be employed for any arbitrary physical environment and multi-antenna structures. Without the loss of generality, the SVW approach is employed to design and analyze a few practical examples to show how effective it can be used for MIMO applications. In conclusion, this research addresses the electromagnetic aspects of the antenna analysis, design, and optimization for MIMO applications in a rigorous and systematic manner. Developing such a design and analysis tool significantly contributes to the advancement of high-data-rate wireless communication and to the realistic evaluation of the MIMO antenna system performance by a robust scientifically-based design methodology.

Multiple-Input Multiple-Output (MIMO) systems are a pivotal solution for the significant enhancement of the band-limited wireless channels’ communication capacity. MIMO system is essentially a wireless system with multiple antennas at both the transmitter and receiver ends. Compared to the conventional wireless systems, the main advantages of the MIMO systems are the higher system capacity, more bit rates, more link reliability, and wider coverage area. All of these features are currently considered as crucial performance requirements in wireless communications. Additionally, the emerging new services in wireless applications have created a great motivation to utilize the MIMO systems to fulfil the demands these applications create. The MIMO systems can be combined with other intelligent techniques to achieve these benefits by employing a higher spectral efficiency. The MIMO system design is a multifaceted problem which needs both antenna considerations and baseband signal processing. The performance of the MIMO systems depends on the cross-correlation coefficients between the transmitted/received signals by different antenna elements. Therefore, the Electromagnetic (EM) characteristics of the antenna elements and wireless environment can significantly affect the MIMO system performance. Hence, it is important to include the EM properties of the antenna elements and the physical environment in the MIMO system design and optimizations. In this research, the MIMO system model and system performance are introduced, and the optimum MIMO antenna system is investigated and developed by considering the electromagnetic aspects within three inter-related topics: 1) Fast Numerical Analysis and Optimization of the MIMO Antenna Structures: An efficient and fast optimization method is proposed based on the reciprocity theorem along with the method of moment analysis to minimize the correlation among the received/transmitted signals in MIMO systems. In this method, the effects of the radio package (enclosure) on the MIMO system performance are also included. The proposed optimization method is used in a few practical examples to find the optimal positions and orientations of the antenna elements on the system enclosure in order to minimize the cross-correlation coefficients, leading to an efficient MIMO operation. 2) Analytical Electromagnetic-Theoretic Model for the MIMO Antenna Design: The first requirement for the MIMO antennas is to obtain orthogonal radiation modes in order to achieve uncorrelated signals. Since the Spherical Vector Waves (SVW) form a complete set of orthogonal Eigen-vector functions for the radiated electromagnetic fields, an analytical method based on the SVW approach is developed to excite the orthogonal SVWs to be used as the various orthogonal modes of the MIMO antenna systems. The analytic SVW approach is used to design spherical antennas and to investigate the orthogonality of the radiation modes in the planar antenna structures. 3) Systematic SVW Methodology for the MIMO Antenna Design: Based on the spherical vector waves, a generalized systematic method is proposed for the MIMO antenna design and analysis. The newly developed methodology not only leads to a systematic approach for designing MIMO antennas, but can also be used to determine the fundamental limits and degrees of freedom for designing the optimal antenna elements in terms of the given practical restrictions. The proposed method includes the EM aspects of the antenna elements and the physical environment in the MIMO antenna system, which will provide a general guideline for obtaining the optimal current sources to achieve the orthogonal MIMO modes. The proposed methodology can be employed for any arbitrary physical environment and multi-antenna structures. Without the loss of generality, the SVW approach is employed to design and analyze a few practical examples to show how effective it can be used for MIMO applications. In conclusion, this research addresses the electromagnetic aspects of the antenna analysis, design, and optimization for MIMO applications in a rigorous and systematic manner. Developing such a design and analysis tool significantly contributes to the advancement of high-data-rate wireless communication and to the realistic evaluation of the MIMO antenna system performance by a robust scientifically-based design methodology.

Ultra-wideband (UWB) offers a high data rate transmission, however it only can be used in short distance communication due to its low power restricted by regulations, therefore it is applicable for an indoor scenario. Within an enclosed (indoor) scenario, there exist many possible multipaths of electromagnetic waves which lead to an effect known as fading [Big07]. Since SISO systems suffer severely from it, in contrast, multiple-output-multiple-input (MIMO) systems take advantage of this multipath/diversity effect. Typical MIMO system utilizes antenna arrays to generate subchannels, but it has no guarantee of orthogonal channels or maximum capacity. Using a new antenna synthesis algorithm, optimal subchannels can be computed by decomposing the MIMO channel into parallel SISO subchannels through the employment of sampling antennas. Thereafter optimal real word antennas can be designed according to the synthesized antenna radiation pattern which result in the reduced hardware. The goal of this thesis will be expressed as follows: Firstly, a good strategy planning to reduce computing effort should be realized since all the design parameters to be analyzed are frequency dependent. Furthermore, a systematic framework of the synthesis must be designed for the UWB band. Lastly, the corresponding real world antenna should be designed and verified. In this thesis, a systematic synthesis framework has be developed and analyzed for the UWB spectrum. The channel matrix acquisition, the design of the ‘sampling antennas’ along with the algorithm to decompose the MIMO channel into parallel independent SISO subchannels are discussed in detail. Two realizations of the real world antennas as well as all the challenges in the design process are also presented. As consequences, an antenna system with optimal radiation pattern has been synthesized. This antenna system radiates orthogonal channels with sufficient power and has fixed beamforming (direction optimized according to the scenario and with averaging over various positions along with rotations) at the transmitter and receiver. The maximum capacity takes into account the scenario, frequency band, physical available space for the antenna array and polarization (added degree of freedom). This work also organizes the antenna synthesis algorithm for UWB in a systematic framework, meeting the objectives of the project. / In this thesis, a UWB antenna synthesis based on the averaging strategies for the predefined indoor communication scenarios has been proposed, which contains both the indoor communication theoretical analysis and real world realization. The algorithm can be applied in an arbitrary indoor scenario over ultra wideband frequency. All synthesized results demonstrated that the designed sampling antenna configuration is able to provide optimized solutions. The synthesis method is based on computing optimal antenna configurations for a MIMO ultrawideband system. In order to maximize the throughput, there exists a sampling volume for both transmit and receive antennas. As such, the face-centered and body-centered cubic antenna arrays are utilized. Given that the system operates in the UWB band with a cognitive feature, the type of antenna, orientation, placement and MIMO diversity scheme have been well investigated. The radiation patterns of the antenna array cover the sampling volume and the bandwidth cover the UWB band. The goal of this thesis work concentrates on the analysis of an indoor communication to find an optimum solution on the antenna configuration and placement. The final objective was to design and realize an optimal MIMO-UWB antenna system. / Add: Waldhornstrasse 19, Karlsruhe, 76131, Germany Tel: +49 176 34467663

SmartWatches are watches with the property that they can connect to internet.The interest and market for smartwatches has increased remarkably over the pastfew years. However, most of today's solutions cover only the frequency bandsBluetooth (BT) and Global Positioning System(GPS). A desired property of thenext generation of smartwatches is to include additional frequency bands suchas Global System for Mobile Communication(GSM) and Third Generation (3G)cellular bands, so that the Smart Watch can become independent of a smartphone.This sets new challenges for antenna design in small regions. The limited sizetogether with the increased bandwidth demand causes the major problem.The purpose of this thesis is to investigate the antenna concept for wrist wear-able devices that has earlier been developed by the RF team at Sunway Commu-nication AB in Stockholm. The main objective of this project is to study howthis antenna concept can be changed to achieve a given set of requirements onfrequency, bandwidth and eciency. Characteristic Mode Analysis and antennaquality factor calculated from the input impedance, are tools used to help under-stand and improve the characteristics of the antenna.A decomposition method and a parametric study were initially applied to theplanar version of the antenna concept. We investigated then the inuence of theposition of the feeds and the slot that separates the two antenna elements. Anoptimised design of the planar antenna was achieved based on the results fromthose studies. Four prototypes of this antenna were built and measured in the RFlaboratory in Kista.The possibility of miniaturization was studied through simulations by analysingthe eect of using a higher dielectric constant material in the antenna. Two dif-ferent arrangements were investigated. The eect of bending the antenna to t ona human wrist was also investigated, where a frequency shift was observed in theresults. The change in bandwidth of the dierent modes is related to the changein the stored energy of the antenna caused by the bending.We made a prototype of the planar antenna that shows a good agreement withsimulation results and fulls the basic requirements on frequency, bandwidth andeciency. We also found that the addition of a shorting pin showed a bandwidthimprovement of the high-band port and we showed through simulation that it ispossible to reduce the size of the antenna by adding a layer of PCABS material.