In recent years, advancements in additive manufacturing (AM) technologies have paved the way for 3D-printed flexible hybrid electronics (FHE) and created opportunities for extending these gains to RF applications. However, printed metal interconnects and devices are typically characterized by high porosity and chemical impurities that significantly limit their electrical conductivity and RF performance compared to bulk equivalents. Using direct ink writing (DIW), two silver inks, a nanoflake suspension and a nanoparticle-reactive ink, were investigated to understand the relationship between free interfacial energy, sintering behavior, DC conductivity, and RF loss. The printed silver samples were characterized using scanning electron microscopy, x-ray diffraction, and x-ray photoelectron spectroscopy to monitor microstructural evolution, grain size and orientation, and chemical purity as a function of heat treatment temperature. Three heat treatments were applied to each ink: the manufacturer's recommendation, 225°C for 30 minutes, and 350°C for 30 minutes. Four-wire structures and coplanar waveguides were printed to compare the DC and RF performance up to 18 GHz, respectively. The results show that ink formulations that facilitate larger grains, high density, and good chemical purity have superior RF performance. A low resistivity of 1.4 times bulk Ag, average of 0.8% greater RF loss factor than evaporated Ag, and a maximum current density of 4.6 x 105 A/cm2 were achieved with printed structures. This work highlights the importance of engineering a high density and high purity microstructure in printed silver components necessary for high-performance printed electronics.

The objectives of this work were to investigate, design and implement beam steering antenna arrays for mobile and wireless applications using the genetic algorithm (GA) and particle swarm optimisation (PSO) techniques as optimisation design tools. Several antenna designs were implemented and tested: initially, a printed dipole antenna integrated with a duplex RF switch used for mobile base station antenna beam steering was investigated. A coplanar waveguide (CPW) to coplanar strip (CPS) transition was adopted to feed the printed dipole. A novel RF switch circuit, used to control the RF signal fed to the dipole antenna and placed directly before it, was proposed. The measured performance of the RF switch was tested and the results confirmed its viability. Then two hybrid coupled PIN diode phase shifters, using Branchline and Rat-Race ring coupler structures, were designed and tested. The generation of four distinct phase shifts was implemented and studied. The variations of the scattering parameters were found to be realistic, with an acceptable ±2 phase shift tolerance. Next, antenna beam steering was achieved by implementing RF switches with ON or OFF mode functions to excite the radiating elements of the antenna array. The switching control process was implemented using a genetic algorithm (GA) method, subject to scalar and binary genes. Anti-phase feeding of radiating elements was also investigated. A ring antenna array with reflectors was modelled and analysed. An antenna of this type for mobile base stations was designed and simulation results are presented. Following this, a novel concept for simple beam steering using a uniform antenna array operated at 2.4 GHz was designed using GA. The antenna is fed by a single RF input source and the steering elements are reactively tuned by varactor diodes in series with small inductors. The beam-control procedure was derived through the use of a genetic algorithm based on adjusting the required reactance values to obtain the optimum solution as indicated by the cost function. The GA was also initially used as an optimisation tool to derive the antenna design from its specification. Finally, reactive loading and time modulated switching techniques are applied to steer the beam of a circular uniformly spaced antenna array having a source element at its centre. Genetic algorithm (GA) and particle swarm optimisation (PSO) processes calculate the optimal values of reactances loading the parasitic elements, for which the gain can be optimised in a desired direction. For time modulated switching, GA and PSO also determine the optimal on and off times of the parasitic elements for which the difference in currents induced optimises the gain and steering of the beam in a desired direction. These methods were demonstrated by investigating a vertically polarised antenna configuration. A prototype antenna was constructed and experimental results compared with the simulations. Results showed that near optimal solutions for gain optimisation, sidelobe level reduction and beam steering are achievable by utilising these methods. In addition, a simple switching process is employed to steer the beam of a horizontally polarised circular antenna array. A time modulated switching process is applied through Genetic Algorithm optimisation. Several model examples illustrate the radiation beams and the switching time process of each element in the array.

The main goals of this thesis are to design and examine heterogeneous antennas for different wireless applications of a wide variety of EM spectrum requirements: which includes WLAN 5.0 GHz, WLAN (2.45 GHz), UMTS (1.92-2.17 GHz), 2G, UMTS, LTE, ultra-wideband (UWB) applications, and MBAN applications (2.4 GHz). Various techniques for expanding bandwidth, enhancing performance, and balancing the operation have been examined through comprehensive simulated and physically fabricated models. Thereafter, a compact DRA, for UWB applications is examined. The combined resultant effects of asymmetric positioning of DRs (2, 3 and 4 Cylindrical elements), defected ground technique, dimensions, and profile of the aperture give RF designers detailed scope of the optimization process. More resonances are achieved, and the bandwidth is improved. The obtained results show that, an impedance bandwidth of 133.0%, which covers the Ultra­ Wideband band (3.6GHz - 18.0GHz), with a maximum power gain of 9dBi attained. In addition, a compact conformal wearable CPW antenna using EBG-FSS for MBAN applications at 2.4GHz is proposed. They are designed using fabric materials suitable for daily clothing. The performance of the antenna is investigated in free space, on a layered biological tissue model, and on a real human body to evaluate SAR. When the antenna is combined with an EBG-FSS structure, isolation between the antenna and the human body is introduced. The results show that the FBR is enhanced by 13 dB, the gain by 6.55dBi, and the SAR is lowered by more than 94%. The CPW antenna demonstrated here is appropriate for future MBAN wearable systems. The design, investigation, and application of water level monitoring utilizing subsurface wireless sensor are covered in this thesis. A wideband double inverted-F antenna is designed and examined to overcome signal attenuation issues. The obtained result is feasible, which has an operating bandwidth of 0.8 to 2.17GHz, with a reflection coefficient better than 10 dB. Moreover, a field trial is conducted to evaluate the robustness of the antenna under extreme conditions. A very good efficiency was also demonstrated, with losses of under 20%. Further, the results from the field experiment established that the antenna is a reliable contender for wireless communication in such challenging environments. / Libyan Ministry of Higher Education / The full text will be available at the end of the embargo: 25th May 2025

Des circuits différentiels sont largement utilisés pour la conception de composants hyperfréquences principalement en raison de leur meilleure immunité au bruit. Ces circuits doivent être caractérisés au moyen de paramètres S en mode mixte (mode différentiel, mode commun et conversion entre les deux modes). De plus, la tendance à la miniaturisation et à l’intégration des dispositifs hyperfréquences conduit à l’utilisation de structures planaires ou coplanaires telles que les lignes micro-ruban ou les lignes coplanaires. La structure coplanaire avec les conducteurs déposés à la surface supérieure du substrat évite de réaliser des trous métallisés, et donc simplifie la fabrication et empêche l’apparition d’éléments parasites. Du point de vue de la métrologie électrique, il est nécessaire d’établir la traçabilité des mesures de paramètres S en mode mixte au Système International d’unités (SI). La méthode d’étalonnage Multimode Thru – Reflect – Line (TRL), dérivée de l’étalonnage TRL couramment utilisée pour les mesures de paramètres S de circuits asymétriques, est bien adaptée à cette problématique. En effet, l’impédance caractéristique, qui définit l’impédance de référence du système de mesure, peut être obtenue à partir des constantes de propagation déterminées lors de la procédure Multimode TRL et des capacités linéiques en DC.Nous présentons la première conception et la réalisation d’un kit d’étalonnage Multimode TRL et d’un kit de vérification à base des lignes coplanaires couplées en configuration « Ground – Signal – Ground – Signal – Ground » sur un substrat de quartz (SiO2) à faibles pertes diélectriques pour des mesures de paramètres S en mode mixte sur wafer de 1 GHz à 40 GHz. Les mesures sont effectuées à l’aide de deux méthodes : l’approche « one-tier » basée sur la procédure d’étalonnage Multimode TRL afin de déterminer et de corriger l’ensemble des erreurs systématiques ou bien l’approche « two-tier » qui fractionne la détermination et la correction des termes d’erreur en deux étapes dont la deuxième est associée à la méthode Multimode TRL. La faisabilité et la validation de ces techniques sont démontrées par des mesures d’éléments de vérification, constitués de lignes (adaptées, désadaptées et déséquilibrées) et d’atténuateurs en T, qui montrent un très bon accord entre les valeurs mesurées et simulées.La propagation des incertitudes est évaluée soit à partir du calcul des dérivées partielles à l’aide de l’outil Metas.Unclib ou bien par simulation numérique basée sur la méthode de Monte Carlo. La précision des mesures de paramètres S sous pointes dépend des sources d’influence attribuées aux mesures et aux imperfections des étalons telles que le bruit et la non-linéarité de l’analyseur de réseaux vectoriel, la stabilité des câbles, la répétabilité des mesures et la sensibilité dans la réalisation des étalons. Faute de temps, nous nous limitons à estimer la propagation d’incertitudes liées à la répétabilité de mesure des étalons et du dispositif sous test (DST) aux valeurs des paramètres S corrigés de la ligne désadaptée. Les résultats montrent que l’approche des dérivées partielles basée sur une approximation de la série de Taylor au premier ordre ne peut pas être utilisée avec précision à cause de l’influence significative de la non-linéarité des fonctions mathématiques de l’algorithme Multimode TRL. La méthode Monte Carlo s’avère alors plus précise bien qu’elle nécessite des temps de calcul très longs. / Differential circuits are widely used in the design of high frequency components mainly because of their better noise immunity. These circuits can be characterized using mixed-mode S parameters (differential- and common-mode S-parameters and cross-mode terms). Furthermore, the trend toward miniaturization and integration of microwave devices increases the need for planar or coplanar microwave integrated circuits such as micro-strip lines or coplanar waveguides. The ungrounded coplanar waveguide structure with all the conductors located on the same side of the substrate eliminates the need for via-holes, and thus simplifies manufacturing and prevents the appearance of some parasitic elements. From the viewpoint of electrical metrology, it is necessary to establish the traceability of the mixed-mode S-parameter measurements to the International System of Units (SI). The Multimode Thru-Reflect-Line (TRL) calibration method, derived from the commonly-used TRL calibration for S-parameter measurements of single-ended circuits, is particularly well suited for this purpose as the standards are traceable via dimensional measurements. The characteristic impedance, which defines the reference impedance of the measurement system, can be achieved from the propagation constants determined during the Multimode TRL calibration and the capacitances per unit length of the transmission line.We present the first design and realization of Multimode TRL calibration and verification kits using coupled coplanar lines in the "Ground - Signal - Ground - Signal - Ground" configuration on quartz (SiO2), the low-loss substrate, for on-wafer mixed-mode S-parameter measurements from 1 GHz to 40 GHz. Measurements are performed using two methods: the “one-tier” technique, based on the Multimode TRL calibration procedure, determines and corrects all systematic errors. The “two-tier” approach, in which the Multimode TRL is applied at the second-tier, is applied to measurement data that were partially corrected by the first calibration. The feasibility and the validation of the methods are demonstrated by measurements of matched, mismatched and unbalanced lines and T-attenuators showing good agreement between simulated and measured results.The propagation of uncertainty can be derived by the calculation of partial derivatives using the Metas.Unclib tool or by the numerical approach based on the Monte Carlo technique. The accuracy of on-wafer S-parameter measurements depends on sources of influence attributed to the measurements and to the imperfections of the standards such as the VNA noise and non-linearity, the cable stability, the measurement repeatability, and the sensitivity in calibration standards’ realization. We focus, first and foremost, on the propagation of uncertainties related to the repeatability of the standards and the device under test measurements to the corrected mixed-mode S-parameters of the mismatched line. The results show that the partial derivatives approach based on an approximation of the first-order Taylor series cannot be accurately used due to the significant influences of non-linear functions in the Multimode TRL algorithm. The Monte Carlo method is then more precise although it requires very long computation time.

This diploma thesis deals with the design and simulation of multi-layer stacked Yagi antenna at the frequency of 60 GHz. At work are proposed and compared two ways of antenna feeding methods. Based on the results obtained, antenna is fed by substrate integrated waveguide. The proposed antenna has been optimized in terms of gain and impedance matching at the specified frequency. The correct functionality of the antenna was verified by simulation program CST MWS 2011. Simulation results were verified experimentally.

This diploma thesis is focused on design of various antenna structures, based on slot antennas, created in the wider wall of a rectangular-shaped waveguide. As the substrate, it is used a 3D textile material, while its properties are examined. They were designed structures, that operate with linear and circular polarization, and other related structures, that are used for feeding and power division. Structures are designed to operate at central frequency of 8 GHz and its vicinity.

Diploma thesis is focused on manufacturing process of waveguide filter. Thesis is divided to 8 chapters. There is summarized theory of possible execution of waveguide filter, used materials, their influence and risks during production. Then are described possible steps of realization and necessary relations for its design, simulation and also practical realization. At conclusion are summarized, compared and described reached results.

The main objectives of this research are to investigate and design low profile antennas for mobile handsets applications using the balanced concept. These antennas are considered to cover a wide range of wireless standards such as: DCS (1710¿1880 MHz), PCS (1850¿1990 MHz), UMTS (1920¿2170 MHz), WLAN (2400¿2500 MHz and 5000 ¿ 5800 MHz) and UWB frequency bands. Various antennas are implemented based on built-in planar dipole with a folded arm structure. The performance of several designed antennas in terms of input return loss, radiation patterns, radiation efficiency and power gain are presented and several remarkable results are obtained. The measurements confirm the theoretical design concept and show reasonable agreement with computations. The stability performance of the proposed antenna is also evaluated by analysing the current distribution on the mobile phone ground plane. The specific absorption rate (SAR) performance of the antenna is also studied experimentally by measuring antenna near field exposure. The measurement results are correlated with the calculated ones. A new dual-band balanced antenna using coplanar waveguide structure is also proposed, discussed and tested; this is intended to eliminate the balanced feed network. The predicted and measured results show good agreement, confirming good impedance bandwidth characteristics and excellent dual-band performance. In addition, a hybrid method to model the human body interaction with a dual band balanced antenna structure covering the 2.4 GHz and 5.2 GHz bands is presented. Results for several test cases of antenna locations on the body are presented and discussed. The near and far fields were incorporated to provide a full understanding of the impact on human tissue. The cumulative distribution function of the radiation efficiency and absorbed power are also evaluated. / UK Engineering and Physical Sciences Research Council (EPSRC)

This project investigates developing and implementing innovative indoornavigation systems by leveraging repurposed Wi-Fi infrastructure anddedicated RFM69HCW transceivers. Aimed at enhancing indoor positioningaccuracy, the study explores the viability of using Received Signal StrengthIndicator (RSSI) and dedicated device localization techniques to overcomethe limitations of existing Global Positioning System (GPS) technology inindoor environments. Through the design and testing of a printed circuit board(PCB) prototype that connects Raspberry Pi Pico (RPP) to RFM69HCWmodules and the development of custom drivers for the RP2040 processor,this research addresses the challenges of indoor navigation, such as signalvariability and environmental interference. The project also emphasizes theimportance of sustainable technology development by repurposing electronicwaste for innovative applications. Findings from the study reveal the potentialof these methodologies to improve indoor positioning accuracy despitechallenges related to hardware compatibility and the dynamic nature of indoorspaces. This research contributes to indoor navigation by demonstrating thefeasibility of using repurposed and dedicated hardware solutions, offeringinsights into future directions for enhancing indoor navigation systems, andhighlighting the role of sustainability in technological innovation.

The main objectives of this research are to investigate and design low profile antennas for mobile handsets applications using the balanced concept. These antennas are considered to cover a wide range of wireless standards such as: DCS (1710-1880 MHz), PCS (1850-1990 MHz), UMTS (1920-2170 MHz), WLAN (2400-2500 MHz and 5000-5800 MHz) and UWB frequency bands. Various antennas are implemented based on built-in planar dipole with a folded arm structure. The performance of several designed antennas in terms of input return loss, radiation patterns, radiation efficiency and power gain are presented and several remarkable results are obtained. The measurements confirm the theoretical design concept and show reasonable agreement with computations. The stability performance of the proposed antenna is also evaluated by analysing the current distribution on the mobile phone ground plane. The specific absorption rate (SAR) performance of the antenna is also studied experimentally by measuring antenna near field exposure. The measurement results are correlated with the calculated ones. A new dual-band balanced antenna using coplanar waveguide structure is also proposed, discussed and tested; this is intended to eliminate the balanced feed network. The predicted and measured results show good agreement, confirming good impedance bandwidth characteristics and excellent dual-band performance. In addition, a hybrid method to model the human body interaction with a dual band balanced antenna structure covering the 2.4 GHz and 5.2 GHz bands is presented. Results for several test cases of antenna locations on the body are presented and discussed. The near and far fields were incorporated to provide a full understanding of the impact on human tissue. The cumulative distribution function of the radiation efficiency and absorbed power are also evaluated.