In the framework of this MSc thesis the analysis of core-shell leaky-wave lens antennas is presented, based on a combination of asymptotic and Physical Optics techniques. This study aims to develop an analysis approach which can be subsequently used for the optimization of the Fly’s Eye antenna concept, through enabling the investigation of shaped variations of the core lens. The main difficulty of this prospect refers to the surface of the core lens being in the near field of the leaky wave feeding structure, since the evaluation of the near field is in general a computationally inefficient process. Adhering to this conclusion, a big part of this thesis elaborates on a very fast approach for the derivation of the near field, through asymptotically approximating the involved integral expressions. More specifically, the presented method exploits the nature of the near field in the examined stratification through introducing an approximation in the integral expressions, which in turn enables their asymptotic evaluation in a straightforward manner. Subsequently, the near field on the core lens is combined with a set of Physical Optics techniques in order to develop a model for the integrated lens architecture of the Fly’s Eye antenna. Modelling the core-shell structure in such a manner enables its study in a much more computationally efficient fashion compared to the use of a full-wave simulator. In addition, it facilitates the investigation of structural alterations in the antenna concept, like shaped variations of the core lens. The derived model presented in this thesis also contributed to the measurement campaign of the Fly’s Eye antenna prototype, through identifying a problematic component in the assembled prototype.

This master thesis explores the capacity of MIMO arrays for communication in the radiative near field through antenna design. This research applies an in-house MATLAB model based on free space Green’s function to calculate the channel matrix, revealing the potential increase of capacity through the use of incoherent arrays with directive antennas in the incoherent range without the need for interference cancellation.

The optimization of the equivalent aperture current and the design of lens antennas are the key points in realizing the ultimate goal of maximizing the capacity between antenna arrays. The accuracy of the channel matrix from the MATLAB model and the performance of the designed lens antennas are validated through full-wave simulation using CST. Furthermore, the internal reflections between the arrays are studied, offering solutions to mitigate the effects of the reflections for future array designs.

This work serves as a feasibility study, providing sufficient confidence in the application of communication systems in the radiative near field without the need for signal processing (e.g. interference cancellation, multi-path cancellation, etc.). Furthermore, the methodology in this thesis offers insights for future antenna designs for different applications. In summary, this study proposes and validates a potential solution for the design of next-generation communication systems.

Planar lenses based on metasurfaces or resonant elements are typically narrowband due to phase wrapping, which is strongly frequency-dependent. On the contrary, true-time-delay (TTD) planar lenses, which do not resort to phase wrapping, can achieve large bandwidths. One convenient way to design wideband TTD lenses is by means of artificial dielectric layers (ADLs), which are stacks of sub-wavelength-period patch arrays embedded in a host medium to increase its effective permittivity to values higher than commercially available dielectrics. The procedure to retrieve the effective refractive index for a given ADL stratification is reported, as well as the synthesis of the multi-section transformers in ADL technology. Trade-offs including bandwidth, focal ratio, lens diameter, and thickness, are discussed and related to the manufacturing constraints of artificial dielectrics, such as the number of metal layers, maximum achievable effective permittivity, and smallest features realizable in printed circuit board technology. An example of design is also presented, operating from 70 to 140 GHz with a lens diameter of 11.5 wavelengths at the highest frequency. A modeling method for the analysis of a flat lens based on ADLs is presented. This consists of a combined geometrical optics (GO) / physical optics (PO) approach, where each GO ray is studied as a plane wave problem to evaluate the reflection/transmission through each unit cell of the lens. This analysis is extended to consider the bending of the rays through the lens and propagation through multiple unit cells.

Within the framework of this thesis, the analysis of the infinite slot leaky wave antenna is presented and a new geometry for the feed of a leaky lens is explored. Firstly, the analysis of the propagating leaky wave modes (TM0 and slot modes) is done leading to the findings about the location of the slot pole w.r.t. k0, as well as the contributions of the leaky waves and how they behave when the thickness of air-cavity and width of the slot change. Secondly, the spectral analysis of the near field is put forward with the goal of gaining deeper understanding of the leaky wave modes’ behaviour and their asymmetry. Finally, a new geometry: leaky wave antenna with multiple slots is explored and its potential of lowering the levels of cross pol. is shown.

WiECG aims to create a prototype device which enable ambulance personnel to perform a 12-lead ECG without wires connecting the patient to the monitor. The proposed solution consists of a transmitter and a receiver device. The transmitter transmits the measured signals, the receiver sends the measured signals to the monitor, which shows the measured signals.
This thesis describes the design and implementation process for the hardware. This concerns the amplification and filtering of the signals produced by the heart of the patient as well as the reconstruction
and attenuation at the output of the receiver module. These processes should be done for 9 signals. Furthermore, component selection, design decisions and the process of implementing this analog signal processing on a printed circuit board is described including the interfaces with the modules used by the other subgroups of this thesis. The prototype built during this project was able to filter the 9 signals and send it from transmitter to receiver while only adding 1.572 V RMS noise to the output ECG signal.

In this thesis, an efficient optimization method is described for synthesizing lens antennas fabricated in low permittivity plastic materials to achieve wide scanning performances. The method is based on an antenna in reception representation. The optimized parameters are the location and orientation of the antenna feeder, lens angular region and its shape by adding Zernike polynomials to standard ellipsoidal shape. The synthesized lens antennas achieve scan losses lower than 3dB while scanning up to 60°. The presented theoretical results are validated using full wave simulations. Furthermore, an efficient analysis method based on Geometrical Optics and ray tracing is developed. This method is applied to the study of multi lens Quasi-Optical structures. The presented theoretical results are validated by multi surface Physical-Optics approach.

The primary goal of this study is to infer a time-domain (TD) counterpart of the frequency domain leaky wave. To reach this goal, a number of challenging problems will be tackled: (1) Develop adequate computational tools for performing detailed TD electromagnetic (EM) analyses via CST Studio simulations, the post-processing of the results included. (2) The TD study of the radiation from a gap-fed long slot at an air-dielectric interface. (3) The TD study of the radiation from a gap-fed long slot located just below an air-dielectric interface. The results of these explorations represent a first step towards establishing a causal counterpart of the leaky-wave radiation.

Lens array architectures are being developed for high frequency applications such as phased arrays for 5G point-to-point communications, Fly’s Eye lens arrays for wideband wireless communications and scanning phased arrays at sub-millimeter wavelengths. Each of these applications employ different feed configurations, lens geometries and require specific feed isolation levels. In these architectures, the mutual coupling between feeds is an important design criteria. This project proposes a theoretical model based on Geometrical Optics and Physical Optics to represent the multiple reflections in a dielectric lens antenna and its impact on the mutual coupling between lens feeders. This model is then employed to study the mutual coupling in architectures with different feed models, edge illumination levels, feed positions, lens diameters and dielectric materials.

Phased arrays have emerged as a key solution for 5G base stations, to provide higher capacity by means of directive and electronically steerable beams. However, the implementation of workable low-cost antenna arrays for base stations is very challenging, because of the requirements on the total frequency and angular coverage of 5G systems. When many frequency bands are used for different services, having a single narrowband antenna for each sub-band becomes unfeasible for cost and space occupation. For this reason wideband arrays that can cover simultaneously multiple bands are gaining interest. Moreover, a large field of view is required, i.e. scanning at least from -60° to +60°, so that only a few array panels can cover the entire azimuthal angle of 360°. This thesis work has been performed in the framework of a collaboration between Terahertz Sensing Group and HUAWEI, aiming at the development of a wideband phased array for base station. Two array designs are targeted, one covering 6-8 GHz and another for 2-8 GHz. Both designs are required to achieve wide scanning capability up to 60° in all azimuth planes. This thesis focuses on the design of the feeding structure of the array unit cell and the corporate feeding networks. The unit cell feeding structure is based on integrated coaxial lines connected to microstrips or striplines. The performance is analysed first for the stand-alone transition and then for the same feed together with the connected slot element. The entire unit cell including the feed has comparable matching performance with the ideal one without feeding structure. An alternative feed design is also presented, where the input is realized with a coaxial SMP connector. The design of a corporate feeding network for the array is introduced. This consists of two designs of 1-to-32 power dividers, one implemented with microstrip transmission lines and the other with striplines. Such dividers are meant to feed in phase an entire row or column of the array. The highlights of this design is wide bandwidth, which covers two octaves by means of wideband multi-section and tapered impedance transformers, and the compactness, since the entire divider has to fit in an area of 480 mm × 15 mm. Moreover a novel feeding strategy is proposed to simplify the complexity and the costs of the unit cell. The new approach is based on replacing the coaxial lines with integrated parallel plate waveguides (PPW). Two examples of unit cell design are presented: one consists in a single-polarized array of connected slot, covering the band from 70 GHz to 140 GHz, for automotive radars; another example is referring to a dual-polarized connected slot array covering the same 2-8 GHz range, for wideband base stations. The design procedure of a PPW and cavity is easier than that of the integrated coaxial, as the feed and the radiating slot design are better decoupled. The number of layers of the ADL is also reduced with respect to the integrate coaxial, because part of the impedance transformation is implemented in the PPW.

The interest for phased array antennas has increased over the past years along with the need for wide bandwidth arrays. Connected arrays are becoming more prevalent as a well suited solution to achieve the desired bandwidth. In order to increase the bandwidth and the scan angle of this type of array, horizontal artificial dielectric supersaturates have been used with good results. However, those superstrates come with an increase in cross polarization. The cross polarization of connected arrays with isotropic dielectric substrates and superstrates is thoroughly investigated in this thesis, along with an analysis on the cross polarization of the connected array with artificial dielectrics. In order to reduce the cross polarization as a result of that superstrate, a novel artificial dielectric is introduced which implements vertical vias to form a wire medium. For this medium a method of moments analysis is performed and a closed form expression is found. Additionally, the wire medium is implemented in the horizontal artificial dielectric to form the top-hat loaded wire medium as a solution to the restricted height between layers of the artificial dielectric slab. The wire medium increases only the z-component, since the wire is oriented vertically, of the effective permittivity without impacting the other effective constitutive parameters. The increase of the refraction index for transverse magnetic wave reduces the cross polarization level and aids in the matching for E-plane scanning, while maintaining a decay over the scan angle. However, a trade off between the reduction in cross polarization and the E-plane scanning is observed. This trade off is a result of the large z-component of the effective permittivity which promotes the propagation of the TM0 surface wave mode. The effectiveness of this novel structure is shown by considered a satellite communication application for simultaneous operation in the Ku- and Ka-transmit bands with a scan angle up to 60 degrees . A design for this application is performed with good matching, -10dB for broadside and -6dB for scanning in both E- and H-plane, and with a low cross polarization level of < −10dB. An evolved design with the manufacturing necessities, such as bonding layers and support layers, is obtained which exhibits a cross polarization level < −15dB with the use of the introduced wire medium, however, the layer height restriction set by the manufacturer and the feeding structure still provide a challenge at the frequency bands which are considered.

When symptoms of atrial fibrillation (AF), a common cardiac arrhythmia, are experienced, a Holter monitor or event recorder is used for official diagnosis. Apart from the fact that these devices are experienced as inconvenient, AF can already manifest damage in a pre-symptomatic phase. This thesis is aimed at developing a method for recording heart activity using a wearable device to permit convenient early detection of AF. For this, heart activity is measured continuously by means of photoplethysmography (PPG). A classification algorithm is used to detect AF episodes in the PPG recording. If the algorithm suspects AF, a limb lead I ECG recording is requested from the user. The ECG recording can be analyzed by a clinician for official diagnosis. The Maxim Integrated Max86150 chip is used for the implementation of PPG and ECG. Acceleration data is gathered by means of the Adafruit MMA8451 accelerometer to allow for detection of motion artefacts. These sensors and the data they retrieve are controlled and processed by the ARM Cortex-M7 microcontroller. From the results, PPG recordings have a higher quality when infrared light is used as compared to when red light is used. However, both types of recordings are of sufficient quality for monitoring the heart rate accurately when in stasis. Although complete functionality of the system could not be verified, the results are promising for future work.

This thesis is concerned with a first time demonstration of a high frequency scanning lens phased­-array with dynamic steering. Such phased­-array could provide the high gain, wide bandwidth, and steering capability that the next generation of wireless ap­plications requires. The phased-­array development was divided into three distinct parts. First, the electronic phase steering system was discussed and developed, and its stability was characterized over time. Results obtained over 24 hours indicated that the system would be stable to within 6° of high frequency output phase. The drifts in output amplitude remained to within 0.3dB. Next, the lens antenna elements were developed with a novel corrugated leaky ­wave feed that provides very high and broadband aperture efficiency. Antenna measurements have validated its ability to be a very aperture efficient radiator (>80%) with wide bandwidth (1:2). Scanning measurements have shown a 3dB scan loss at around 15°. Finally, the phase steer­ing and antenna elements were combined into a 4×1 array concept. Its behaviour was simulated and indicated again good performance with wide bandwidth (1:2) and high directivity (31.5dBi). Simulated scan loss was approximately 3dB at 20°. The amplitude and phase errors resulted in a SLL standard deviation of 0.63dB. The array prototype is currently awaiting completion of fabrication by DEMO at the TU Delft.

The goal of this graduation project was to design a state-of-the-art central farm controller. The designed central farm controller distinguishes itself from prevailing controllers by including a subsystem (the optimisation unit) that contributes to an improvement in power transmission effciency, decrease in maintenance costs and an increase in system reliability/robustness. This thesis describes the design process of the optimisation unit and the verifcation of its feasibility. Originally, the plan was to test the design on a remote terminal unit (RTU), but unfortunately due to the current crisis, this was not possible. Therefore, the implementation and testing were carried out only in MATLAB. Tests were performed using a MATPOWER system model which has been derived from a real wind farm topology. The optimisation unit makes use of a meta-heuristic algorithm to solve an optimal reactive power flow dispatch optimisation problem. In this thesis, the feasibility of this optimisation unit is investigated. Furthermore, it is determined which devices should be controlled and of which the usage is optimised. This makes the treated optimisation problem a multiple objective optimisation. Lastly, the robustness is verified by extending the topology and testing the solutions of the optimisation unit.

This report details the design of an instrumentation system to be used on a skeleton sled. The system will measure data during the run on a skeleton track using several sensors and process and visualise the data afterwards in order to shorten the learning curve of the athlete and give quantitative feedback. The subsystem discussed in this report concerns the measurement of the forces between the body and the sled in order to analyse the steering behaviour of the athlete. This is accomplished via thin film resistive force transducers. The g-forces on the athlete and the sled and the orientation of the sled are measured as well in order to give a better insight how this influences steering and is measured using an IMU (Inertial Measurement Unit). The data is collected using an ESP32 microprocessor.

In this work, a MATLAB based graphical user interface (GUI) tool is built to analyze Quasi-optical (QO) systems in reception with the Fourier Optics (FO) and Geometrical Optics (GO) methods. Five canonical QO components are discussed, namely parabolic reflectors, elliptical lenses, hemispherical lenses, hyperbolic lenses, and elliptical mirrors. The ray tracing technique is implemented to describe reception scenarios and visualize the phase aberrations in the QO systems. The FO method represents the fields focalized by a QO component on its focal plane as a Plane Wave Spectrum (PWS). This spectrum is calculated by using the GO method and can be used in spectral techniques like equivalent Floquet circuit. Moreover, the tool is able to use this spectrum to estimate the power delivered to an antenna placed at the focal plane. By obtaining this delivered power, the performance of the antenna-coupled QO system is analyzed, including pattern, directivity, common efficiency terms, and gain. In addition, the performance calculated in reception is validated by CST and GRASP full-wave simulation software. Therefore, this GUI tool represents a GO/FO based tool that can be used to analyze and design antenna-coupled QO systems in reception.

Typical antenna arrays are designed such that the active element pattern is symmetric around the broadside direction. However, applications exist, for example in satellite communication, where a symmetric pattern is not needed or even unwanted. This angular selectivity can be achieved using asymmetric elements. However, it is known that for well sampled infinite arrays the asymmetry of the active element pattern disappears. Although designs of under-sampled antenna arrays achieving an asymmetric active element pattern have been presented in literature, the fundamental properties of this type of arrays in terms of radiation characteristics have not been investigated in detail. This thesis studies the asymmetry in the active element pattern of a finite linear array of asymmetric elements. To this end an in-house method of moments code is developed in Matlab to simulate tilted dipoles in free space and in the proximity of a ground plane. The dependency of the asymmetry of the active element pattern on the inter-element distance, the skew angle of the elements and the number of elements in the array is analyzed and design rules are derived. Using entire domain basis functions, closed form expressions for spectral integrals and the periodicity of the array the implemented code enables the simulation of large arrays in a much shorter time compared to commercially available software, such as CST.

Regarding the choice of antenna element, a dipole bent into a Z-shape is proposed as an alternative for a tilted dipole. This type of dipole can be defined to have an equivalent radiation pattern to that of a tilted dipole. This shape of dipole can be implemented using standard PCB technology using horizontal metal strips and vertical vias. The Z-shaped dipoles are analyzed using a method of moments code based on horizontal and vertical dipoles. The spectral Green's function of stratified media can be included in the spectral domain expressions to account for the presence of dielectric slabs in realistic designs.

In this work, the analytical models to describe artificial dielectric layers (ADLs), when a lateral shift between layers is present, is presented. The alternate lateral displacement between layers is an important parameter to engineer the desired effective electromagnetic properties of the equivalent homogeneous material realized with the ADLs. More specifically, the equivalent dielectric constants that can be realized by alternatively shifting the layers are higher compared to the aligned case. Closed-form expressions are derived for the equivalent layer reactance that includes the higher-order interaction between shifted layers. Furthermore, the effect of finite conductivity of the metal patches is studied and included to the extended versions of the formulas. The given analytical formulas can be used to derive an equivalent circuit model that describes the scattering parameters of a plane wave impinging on a slab composed by an arbitrary finite number of metal layers. To aid the design of artificial dielectric slabs, the effective permittivity and permeability tensors are also retrieved from the scattering parameters.