Active phased array antennas, generally consisting of a large number of antenna elements and integrated-circuit (IC) components, are essential for different applications like 5G/6G communications, radar, aerospace, satellite communications and so on. The study of radiation pattern measurements and analysis of pattern data is a pivotal step in characterizing and understanding the use of antennas in any application. Unwanted changes can be observed in the radiation pattern due to randomly failed elements, ICs, or IC channels in phased arrays. Hence, there is a vital need for fast testing and diagnosis to identify possible failures of these large antenna systems, before taking any immediate action to compensate for these changes. Due to integrated-circuits (IC) non-linearities and mutual coupling challenges, the existing deterministic and optimization-based fault detection techniques fail to provide reliable results in practical systems. Besides, it is desired to achieve real-time array diagnosis during in-field operation, which makes the problem even more challenging. In this thesis, a novel machine-learning assisted fault-detection algorithm is proposed which is trained by using sparse far-field measurements from a practical IC-integrated millimeter-wave (mm-wave) phased array prototype and fixed multi-probe measurement system (antenna dome). A global optimization approach is used as a benchmark for comparison to the state-of-the-art. The incorporation of machine learning techniques greatly improves the fault detection time and accuracy in comparison to global optimizers. Furthermore, studies based on the number of sampling points used and the varying number of faults are also conducted which indicate similar conclusions.

As the world is getting used to 5G technology, 6G is already on the horizon. With the ultimate goal of very low latency communication and Tbps data rates, 6G supports new wireless technologies such as virtual and augmented reality and autonomous driving. In this new generation of wireless communication, high frequencies up to 100 GHz are used which causes antenna arrays to shrink to the size of a post stamp. Antenna-in-Package (AiP) is an emerging technology that integrates these antennas directly in the packaging material of IC’s. This brings the benefit of high level of integration, making beamforming IC’s an all in one system for communications. Despite this, high integration also comes with challenges. These small antenna systems generate heat on a small footprint which emphasizes the need for a low-loss, efficient system. Moreover, free-space path loss is proportional to frequency so high radiated power is needed, further emphasizing the need for improved efficiency. Lastly, space inside the IC and package material is limited which requires compact solutions for the system’s components. Literature has shown that PA-antenna co-design can reduce losses at the PA-antenna interface by matching the antenna impedance to the impedance of the power amplifier, omitting the need for lossy impedance matching networks. This method, called direct impedance matching, has shown to improve power added efficiency (PAE) in antenna systems with single radiating elements and fixed linear arrays. Nevertheless, the advantage of direct impedance matching has not yet been demonstrated for phased array antennas with active beam forming/steering.

This work demonstrates a novel analysis of PA-antenna co-design at 96 GHz using a 8x8 cavity-backed dual-polarized pin-fed stacked patch array. Two versions of this antenna array are designed in Ansys HFSS, one with an antenna impedance of 50 Ω, the benchmark, and one with a lower impedance of 25 Ω. Both designs are made on a custom package laminate stack-up and are compatible with pin-fed AiP technology. Using Keysight ADS, the antenna designs are co-simulated with an RF front-end circuit comprised of a single tone AC signal, ideal 1-64 channel power divider, ideal continuous phase shifters and realistic SiGe Class A cascode power amplifiers. In this setup, the 50 Ω reference antenna is connected to the PA’s with a matching network in between. Because the 25 Ω antenna array matches the optimal output impedance of the PA, it is directly connected. The performance of both antenna arrays are compared, with the focus on PAE and radiation characteristics. The results show that by going for a directly matched antenna the PAE of the system increases by 15.6% for a broadside beam and 30.4% with a scanned beam (θ = 45◦, φ = 45◦). EIRP for broadside and scanned beams increased from 50.3 W to 56.3 W and from 31.1 W to 37.9 W respectively. Bandwidth, gain, radiation efficiency and side-lobe levels were similar in both arrays but the 25 Ω antenna had 4 dB higher levels of cross-polarized radiation and a 4 dB stronger back-lobe behind the antenna. The advantage of higher efficiency and radiated power outweighs these drawbacks and makes direct impedance matching a good design strategy for 6G beamforming AiP technology.

Radiation pattern measurements is a critical step in characterizing antennas before they are used in any system for a specific application. To identify any defects or to acquire the true radiation characteristics of the antenna under test, densely sampled measurements are desired. However, this results in a time and cost expensive measurement process. Compressed sensing allows accurate reconstruction of radiation patterns using a reduced number of measurements. To ensure exact recovery, it is necessary to select an optimal sampling strategy as well as an effective reconstruction method.

In this thesis, the discrete Fourier transform and spherical harmonic expansion of the electric field are used to obtain a sparse representation of radiation patterns. As a variation from the basis pursuit optimization problem which is widely used in compressed sensing for antenna measurements, a sparsity enhancing weighted l1-norm minimization problem is considered. The weights are determined from prior information on antenna from electromagnetic simulations. The proposed method, after investigation with various antennas and comparison with existing benchmark results in a further reduction of number of required measurements. A near-optimal sampling technique is adopted to acquire measurement in an incoherent manner for exact recovery of the pattern. The performance of the method has been evaluated using error metrics specific to important parameters of the radiation pattern such as the gain, peak side lobe level and half power beam width. Radiation patterns with non-idealities and distortions have also been recovered with high accuracy from a small number of measurements using the proposed method.

Increasing wireless communication requirements of data rates, capacity and coverage, and evolution and maturation of wireless equipment prompt wireless communication research insight concentrating on millimeter wave (mm-wave) frequency. However, high reflection coefficients and high path loss cause large shadow areas (e.g. behind the buildings) and poor coverage, leading to constraints on wireless connectivity and effectiveness of wireless communication. Intelligent Reflecting Surface (IRS) is a revolutionizing technology in 6th-generation mobile networks (6G), which achieves extended coverage with reducing construction and electricity costs via its characteristics of passive beamforming and proper deployment, and auxiliary of Ray Tracing (RT) facilitates obtention and analysis of channel state information (CSI) at different locations. With the objective of developing a flexible RT tool and a novel methodology for optimal IRS deployment to maximize coverage in non-line-of-sight (NLOS) areas from the BS, a new RT simulation model is built in this thesis project in accordance with measured data, leading to improved reliability and accuracy of 5.3\% maximum error in path loss. And a novel, but preliminary, weight graph methodology is proposed for tackling the IRS deployment problem for coverage extension in NLOS areas quasi-optimally. To integrate the IRS with RT simulation, a first-time comparison between metal reflectors and IRS under realistic EM effects is exploited. The obtained simulation results unveil that deploying IRS with the proposed weight graph methodology facilitates wireless coverage improvement, and the coverage probability increased from 0% to 96.23% with a threshold of -75 dBm under 28 GHz in a selected Region of Interest (RoI).

The mm-wave operational band (24-30 GHz) is becoming increasingly important for various practical applications. However, at such high frequencies, the issue of propagation losses arises, emphasizing the necessity for these systems to achieve high radiation efficiency. Dielectric Resonator Antennas (DRA) are promising candidates to replace traditional radiating elements like patches since they do not suffer from conductor losses and have a radiation efficiency of over 90% when suitably excited. Additive manufacturing has emerged as a promising technique for producing DRAs due to its numerous benefits, such as the ability to fabricate complex shapes and structures, rapid prototyping, and reduced waste. Additionally, 3D printing can enable the incorporation of varying permittivities within the DRA, further enhancing its performance. The influence of such permittivity profiles in DRAs, particularly in finite phased array setups, is yet to be thoroughly investigated. It is important to understand the impact of this technique on the mutual coupling, cross-polarization, and scanning performance of the array. In this work, we discuss the theory behind the radiation characteristics, the modelling of the DRA designs and the analyses of these designs based on performance criteria such as bandwidth, coupling, gain, cross-polarization and axial ratio bandwidth. This thesis demonstrates for the first time, to the best of author’s knowledge, that the incorporation of permittivity profiles in mm-wave DRAs can improve the bandwidth by 7%, reduce the cross-polarization (at broadside) by around 3 dB and improve the axial ratio bandwidth by around 10% compared to single-permittivity DRAs. Furthermore, it is also shown that in an array environment, the active S-parameters of the elements are better matched across a wider frequency band, upon scanning from 0 to 45 degrees, when a permittivity profile is used.

Hybrid beamforming (HBF) architecture provides promising trade-offs between the system performance and computational/hardware complexity in practical implementations of millimeter wave (mm-Wave) massive multiple-input multiple-output (mMIMO) 5th generation (5G) mobile networks compared to its fully digital beamforming (DBF) counterpart. In this thesis, we investigate the future applicability of deploying hybrid beamforming architectures with subarray beam pattern shaping for mm-Wave 5G base stations in spatially heterogeneous user distributions and different propagation scenarios. We propose HBF structures with a cosecant-squared pattern and a flat-top pattern as well as their HBF and DBF benchmarks. In addition to the uniform user distribution, three non-uniform user distributions, i.e., the near-site distribution, the cell-center distribution, and the cell-edge distribution are proposed to represent the traffic flow and mobility of users due to festivals and holidays. We evaluate the performance in a novel 5G new radio (NR) system-level simulation (SLS) model. Numerical results show that the HBF architecture with a cosecant-squared subarray beam pattern is more robust against differences in spatially heterogeneous traffics than the flat-top HBF and benchmark HBF under the line-of-sight (LoS) propagation scenario. Under the non-line-of-sight (NLoS) propagation scenario, more deterministic environment information and radio channel modeling are required to improve the system performance of the shaped HBF beamforming technique.

With the development of the fifth generation (5G) technologies and beyond, the requirements for future wireless communication systems become more stringent, which demand novel antenna design at millimetre waves. The most commonly proposed array topology for 5G usage is square 8x8 or 16x16 microstrip patches with the full digital beam-forming method. Such designs result in massive complexity, high power consumption, and heat generation, especially with the full digital beam-forming method. To reduce design complexity and power consumption, the hybrid beam-forming is proposed, in which the linear subarrays are used with a fixed beam pattern in elevation, and combined in an array with digital beam-forming to realize the beam scanning in azimuth. Recent studies in the MS3 group at TU Delft have demonstrated that the series-fed subarray can be used in hybrid beam-forming and can realize any desired pattern by independent control of amplitude and phase on each unit cell. However, the main drawbacks of the series-fed arrays are the radiation beam squint and pattern distortion under different frequencies, which can limit the radiation bandwidth. Therefore, it is necessary to investigate the design of the series-fed antenna arrays to reduce the beam squint and pattern distortion. In this thesis, the performance of series-fed antenna arrays radiating the csc2-shaped beam pattern is investigated in terms of beam squint and pattern distortion. The RMS value is used in this thesis to quantify the pattern distortion in series-fed arrays and is used as a performance metric. Firstly, seven types of edge-fed series-fed subarrays are designed and optimized in CST. Their performance in terms of beam squint and pattern distortion is evaluated with and without considering the mutual coupling effect. Then, the subarray with the most stable radiation pattern over the evaluated frequency band (25 GHz - 27 GHz) is selected. Following this, the center-fed series-fed proximity-coupled subarray is designed aiming to reduce the amount of beam squint while having a stable radiation pattern. The performance of the center-fed subarray is compared with the edge-fed configuration in terms of the beam squint and pattern distortion. The simulation results show that the center-fed configuration can significantly reduce the beam squint but can increase the pattern distortion. Finally, the array of center-fed series-fed proximity-coupled subarrays is designed and simulated in CST. The results show that the array is able to reduce the beam squint (within 1°) while having a reasonable pattern distortion (around 20% difference compared to the synthesized pattern) within the frequency range from 25.8 GHz to 26.5 GHz.

Hip replacement surgery, also termed total hip arthroplasty, is a surgical intervention intended to substitute a deteriorated or dysfunctional hip joint with an artificial prosthesis. This procedure is commonly indicated for individuals experiencing severe hip discomfort resulting from conditions like osteoarthritis, rheumatoid arthritis, hip fractures, or other hip-related issues that significantly impair mobility.

Globally, more than 1 million total hip replacement surgeries are conducted annually. Given the substantial mechanical loads experienced by hip implants during regular activities, a thorough understanding and early identification of potential issues before implant failure are imperative. Continuous monitoring of strain is crucial to assess how the implant responds to various stresses over time. This monitoring aids in evaluating the implant’s durability and performance under diverse stress conditions, enabling proactive interventions, if necessary, to prevent critical failures.

Strain monitoring acts as a diagnostic tool to assess the implant’s status and the surrounding tissues. Deviations in strain patterns may signify problems such as implant loosening, wear, or bone loss around the implant. Moreover, this monitoring technique helps customize rehabilitation programs and recommend specific activities based on individual strain levels. Consequently, this tailored approach enhances recovery outcomes while mitigating associated risks.

This project involves the development of a passive wireless resonant circuit that will be used in the future in a sensor designed to detect strain on hip implants for early failure detection. The strain is anticipated to cause fluctuations in the frequency. To evaluate the LC (inductor-capacitor) resonator design at a specific frequency, a simulation model was established using the Computer Simulation Technology (CST) Microwave Studio as the simulation platform. The fabrication of this LC resonant circuit employs cleanroom techniques and protocols to ensure precision and reliability in its structure. Subsequent to fabrication, the resonator underwent characterization employing an antenna to ascertain resonance frequency alterations in accordance with theoretical expectations. The results indicated a detectable shift in resonant frequency corresponding to designs representing different strains.

An exponential growth in the mobile communications industry over the past decade has raised concerns over it’s energy consumption, especially in light of the current climate crisis. 5G technologies in particular exhibit features that imply high power consumption, such as the densification of 5G base stations. Implementing mitigation measures requires accurate a priori knowledge of the power consumption of 5G array architectures in various scenarios; however, there are large gaps in the literature on this topic, and existing power consumption models for 5G array architectures only address a limited scope of use cases and array topologies. Recent works have focused on the energy efficiency of array architectures, but not on the actual amount of power being consumed.

In this thesis, an integrated system-level power consumption model is devised for 5G base station multi-beam transmitter topologies and beamforming schemes, which accounts for the use cases and architectures missing from the literature. The model is then applied to novel use cases in the enhanced urban Mobile Broadband (eMBB) scenario to obtain the estimated power consumption per component, per array and per user for five different beamforming schemes. A thorough parametric analysis is conducted for the optimality and trade-offs of each use case. Recommendations are made on the optimal topology, beamforming scheme and front-end technology from a power consumption perspective. Initial results show that the choice of technology, architecture and topology can lead to an improvement in the per-user power consumption of 41-80%.

With the increasing demand for network services and a growing number of users, 5G communication systems have stringent requirements to fulfill. Due to this reason, 5G systems should employ capacity­-oriented base station antenna arrays and beamforming techniques. In this regard, multibeam antenna systems have gained immense attention. Currently, there is a missing link between antenna engineering and communication system design. Traditionally, antenna array design focused on optimizing free space propagation parameters like gain, directivity, sidelobe levels, etc. However, in order to achieve maximum network capacity, antenna array and beamforming techniques should consider a realistic system model and propagation environment. In this thesis work, we bridge the gap between antenna engineering and communication system design by proposing a multi­user communication system model that considers channel modeling, modulation, and RF aspects. Further, we use this model to assess the user performance in terms of Error Vector Magnitude (EVM) and Bit Error Rate (BER) for various base station antenna configurations and user positions. The results obtained showed that using an irregular antenna array at the base station with 64 elements shows an improvement in the performance of the users. With the presented simulation results, the system engineers can design efficient antenna arrays at the base station to achieve good performance on the millimeter wave frequency bands.

The development of fifth-generation (5G) technology is the beginning of a rapid transition in the world of wireless communications. Gbps data rates, minimal latency, and good connectivity are the ultimate aims of 5G. To achieve them, 5G systems employ the mm-Wave frequency band which has a frequency range above 24GHz and so allows for higher bandwidth and gigabit wireless services. Because the size of the antenna elements and their spacings are so small in mm-Wave, massive antenna arrays in the base station may fit into a smaller area while yet providing high gain. However, the problem with the mm-Wave integrated antenna array system is the excessive heat generated per unit volume as there is not enough surface area to dissipate heat. Thermal management of the antenna system is very important as it affects the reliability and lifetime of the electronic components in the system. Both active and passive cooling strategies have been employed with passive cooling being the cost-effective and energy-efficient solution. Heatsink antennas can enhance the cooling capacity by providing dual functionality in terms of both thermal and electromagnetics. Traditionally, most of the works on heatsink antennas are focused at lower frequencies and a few at the mm-Wave frequency range. However, proper mm-wave thermal modeling in active integrated antennas is missing and there isn’t any research on the performance of heatsink antennas in array designs. This thesis work aims in designing and optimizing a heatsink antenna operating at 28 GHz to achieve dual functionality. The second aim of the thesis is to develop an appropriate thermal model for the designed antenna. Following the conduction-based simulations depending on assumed heat transfer coefficients, proper thermal modeling with appropriate beamformer chip characteristics and a CFD-based natural convective simulation setup has been developed without the assumption of a heat transfer coefficient. Optimal heatsink antenna dimensions are chosen based on the electro-thermal performance. Then, the selected antenna has been used in 1D and 2D arrays. Finally, a comparison study has been made with that of the conventional patch antenna. The results obtained have shown that both 1D (1x8) and 2D (4x4) heatsink antenna arrays can achieve a better heat dissipation by lowering the junction temperature of about 10-20 degrees Celsius (for the investigated cases) with higher realized gain and similar side lobe level compared to the respective patch antenna arrays. Furthermore, amplitude tapering of the heatsink antenna array achieved lower sidelobe levels which make this heatsink antenna a low-sidelobe and low-temperature alternative for the patch antenna array.