Miniaturized RF Components With A Novel Tunable Engineered Substrate For Wireless Communication Systems

There is an increasing demand for reliable sensor system capable of remote sensing and measuring interesting data. Although large communication range can be achieved, active wireless communication systems are still suboptimal in longtime applications due to their harmful battery supply. Inductively coupled passive devices, with the advantages in safe long-term implanting, structural simplicity, small fabrication footprint and low-cost production, are preferred in chronic monitoring, but little work has been done to optimize the performance of these systems, especially under some design constraints. The model and optimization of an inductively coupled wireless pressure sensor system is presented in this dissertation. With MEMS and semiconductor technology, the pressure sensor is designed as a miniaturized LC resonant circuit operating in 402MHz within a small footprint of 3.2 mm by 3.2 mm. An optimization approach is conducted to analyze inductive as well as pressure sensitivity. With mutually dependent geometrical parameters and performance related RF characteristics considered in the full optimization of the system, the applied design of this experiment method can reduce the large number of combined groups of values in fractional simulations with a focus on a few performance related factors. The second task of this research is to improve the limited working range of the sensing system. A half-active wireless communication system is studied as an alternative solution to this problem. Wireless power harvesting circuits and auxiliarydata-acquisition circuits are integrated in the system for long distance communication. However, physical size of system also becomes large with the added circuits. The challenges of designing compact wireless communication system are proposed to be solved in this dissertation. With the requirements of multi-band and multi-function in wireless communication systems with improved performance and reduced size, development of tunable miniaturized RF components are a promising solution to fulfill the trend. Many technologies have been investigated and applied to develop tunable devices including MEMS and semiconductor varactors, ferroelectric capacitors, and magnetically tunable inductors with ferromagnetic materials, etc. However, the tunability of reported devices using the above technologies is directly dependent on the individual design configurations, which limits the design flexibility and broader application. A unique solution is to design arbitrary tunable RF components using an engineered substrate with an embedded patterned permalloy (Py) thin film which was developed for the first time in this dissertation. With high and current-dependent permeability, an engineered substrate embedded with Py thin film is a promising and flexible approach to design compact frequency-agile RF devices. Py thin film is patterned into slim bars on an engineered substrate to improve its ferromagnetic resonant frequency (FMR) for RF and mmwave applications. Miniaturized RF components are first developed with the proposed engineered magneto-dielectric substrate in this dissertation. Permeability tunable smart substrate was also developed by integrating an array of DC bias lines to provide a tuning path of Py patterns. The design principles and factors affecting the characteristics of the engineered substrate have been fully analyzed. Design efficacy of the developed tunable substrate has been demonstrated with implemented components including a patch antenna, a phase shifter, a bandpass filter, and a three-port bandpass filtering balun. The proposed engineered substrate is feasible in implementing arbitrary RF and microwave devices with improved tuning capability and design flexibility

Wireless Sensors and Actuators for Structural Health Monitoring of Fiber Composite Materials

This work evaluates and investigates the wireless generation and detection of Lamb-waves on fiber-reinforced materials using surface applied or embedded piezo elements. The general target is to achieve wireless systems or sensor networks for Structural Health Monitoring (SHM), a type of Non-Destructive-Evaluation (NDE). In this sense, a fully wireless measurement system that achieves power transmission implementing inductive coils is reported. This system allows a reduction of total system weight as well as better integration in the structure. A great concern is the characteristics of the material, in which the system is integrated, because the properties can have a direct impact on the strength of the magnetic field. Carbon-Fiber-Reinforced-Polymer (CFRP) is known to behave as an electrical conductor, shielding radio waves with increasing worse effects at higher frequencies. Due to the need of high power and voltage, interest is raised to evaluate the operation of piezo as actuators at the lower frequency ranges. To this end, actuating occurs at the International Scientific and Medical (ISM) band of 125 kHz or low-frequency (LF) range. The feasibility of such system is evaluated extensively in this work. Direct excitation, is done by combining the actuator bonded to the surface or embedded in the material with an inductive LF coil and setting the circuit in resonance. A more controlled possibility, also explored, is the use of electronics to generate a Hanning-windowed-sine to excite the PWAS in a narrow spectrum. In this case, only wireless power is transmitted to the actuator node, and this lastly implements a Piezo-driver to independently excite Lamb-waves. Sensing and data transfer, on the other hand, is done using the high-frequency (HF) 13.56 MHz. The HF range covers the requirements of faster sampling rate and lower energy content. A re-tuning of the antenna coils is performed to obtain better transmission qualities when the system is implemented in CFRP. Several quasi-isotropic (QI) CFRP plates with sensor and actuator nodes were made to measure the quality of transmission and the necessary energy to stimulate the actuator-sensor system. In order to produce baselines, measurements are prepared from a healthy plate under specific temperature and humidity conditions. The signals are evaluated to verify the functionality in the presence of defects. The measurements demonstrate that it is possible to wirelessly generate Lamb-waves while early results show the feasibility to determine the presence of structural failure. For instance, progress has been achieved detecting the presence of a failure in the form of drilled holes introduced to the structure. This work shows a complete set of experimental results of different sensor/-actuator nodes

Wave-based sensor, actuator and optimizer

Programa doutoral em Sistemas Avançados de Engenharia para a Indústria (AESI)A presente tese explora a utilização de ondas para abordar dois desafios significativos na indústria automóvel. O primeiro desafio consiste no desenvolvimento de um sistema de cancelamento ativo de ruído (ANC) que possa reduzir os ruídos não estacionários no compartimento de passageiros de um veículo. O segundo desafio é criar uma metodologia de conceção ótima para sensores de posição indutivos capazes de medir deslocamentos lineares, rotacionais e angulares. Para abordar o primeiro desafio, foi desenvolvido de um sistema ANC onde wavelets foram combinadas com um banco de filtros adaptativos. O sistema foi implementado em uma FPGA, e testes demonstraram que o sistema pode reduzir o ruído não estacionário em um ambiente acústico aberto e não controlado em 9 dB. O segundo desafio foi abordado através de uma metodologia que combina um algoritmo genético com um método numérico rápido para otimizar um sensor de posição indutivo. O método numérico foi usado para simular o campo eletromagnético associado à geometria do sensor, permitindo a maximização da corrente induzida nas bobinas recetoras e a minimização da não-linearidade no sensor. A minimização da não-linearidade foi conseguida através do desenho (layout) das bobinas que compõem o sensor. Sendo este otimizado no espaço de Fourier através da adição de harmónicos apropriados na geometria. As melhores geometrias otimizadas apresentaram uma não-linearidade inferior a 0,01% e a 0,25% da escala total para os sensores de posição angular e linear, respetivamente, sem calibração por software. O sistema ANC proposto tem o potencial de melhorar o conforto dos ocupantes do veículo, reduzindo o ruído indesejado dentro do compartimento de passageiros. Isso poderia reduzir o uso de materiais de isolamento acústico no veículo, levando a um veículo mais leve e, em última análise, a uma redução no consumo de energia. A metodologia desenvolvida para sensores de posição indutivos contribui para o estado da arte de sensores de posição eficientes e económicos, o que é crucial para os requisitos complexos da indústria automóvel. Essas contribuições têm implicações para o desenho de sistemas automotivos, com requisitos de desempenho e considerações ambientais e económicas.This thesis explores the use of waves to tackle two major engineering challenges in the automotive industry. The first challenge is the development of an Active Noise Cancelling (ANC) system that can effectively reduce non-stationary noise inside a vehicle’s passenger compartment. The second challenge is the optimization of an inductive position sensor design methodology capable of measuring linear, rotational, and angular displacements. To address the first challenge, this work designs an ANC system that employs wavelets combined with a bank of adaptive filters. The system was implemented in an FPGA, and field tests demonstrate its ability to reduce non-stationary noise in an open and uncontrolled acoustic environment by 9 dB. The second challenge was tackled by proposing a new approach that combines a genetic algorithm with a fast and lightweight numerical method to optimize the geometry of an inductive position sensor. The numerical method is used to simulate the sensor’s electromagnetic field, allowing for the maximization of induced current on the receiver coils while minimizing the sensor’s non-linearity. The non-linearity minimization was achieved through its unique sensor’s coils design optimized in the Fourier space by adding the appropriate harmonics to the coils’ geometry. The best optimized geometries exhibited a non-linearity of less than 0.01% and 0.25% of the full scale for the angular and linear position sensors, respectively. Both results were achieved without the need for signal calibration or post-processing manipulation. The proposed ANC system has the potential to enhance the comfort of vehicle occupants by reducing unwanted noise inside the passenger compartment. Moreover, it has the potential to reduce the use of acoustic insulation materials in the vehicle, leading to a lighter vehicle and ultimately reducing energy consumption. The developed methodology for inductive position sensors represents a state-of-the-art contribution to efficient and cost-effective position sensor design, which is crucial for meeting the complex requirements of the automotive industry.I would like to thank the Fundação para a Ciência e Tecnologia (FCT) and Bosch Car Multimedia for funding my PhD (grant PD/BDE/142901/2018)

High dynamic range optical devices and applications.

Much of what we know about fundamental physical law and the universe derives from observations and measurements using optical methods. The passive use of the electromagnetic spectrum can be the best way of studying physical phenomenon in general with minimal disturbance of the system in the process. While for many applications ambient visible light is sufficient, light outside of the visible range may convey more information. The signals of interest are also often a small fraction of the background, and their changes occur on time scales so quickly that they are visually imperceptible. This thesis reports techniques and technologies developed for sensing and detecting rapid transient phenomenon using ambient light in the infrared (IR) spectrum. Currently, high dynamic range optical sensor technology leveraging low-noise and real-time signal processing is employed for applications to human, animal and structural health monitoring, Earth surface motion and environmental monitoring, material defect analysis and astronomy. This work describes the development and fabrication of devices that are made using a novel 32-bit data acquisition system (DAQ), as well as custom-designed circuits for integrating current optical sensing devices into systems for such applications. This thesis also describes the design, construction, and application of an impulse generator for materials testing and a custom-designed Ethernet-connected automated optical fiber positioning stage with examples of their applications to passive non-contact optical sensing

Electromagnetic Wave Propagation for Industry and Biomedical Applications

This book highlights original research and high-quality technical briefs on electromagnetic wave propagation, radiation, and scattering, and their applications in industry and biomedical engineering. It also presents recent research achievements in the theoretical, computational, and experimental aspects of electromagnetic wave propagation, radiation, and scattering. The book is divided into three sections. Section 1 consists of chapters with general mathematical methods and approaches to the forward and inverse problems of wave propagation. Section 2 presents the problems of wave propagation in superconducting materials and porous media. Finally, Section 3 discusses various industry and biomedical applications of electromagnetic wave propagation, radiation, and scattering

Eddy current angular position sensor for automotive

Programa doutoral em Líderes para Indústrias TecnológicasOs sensores angulares usados em aplicações automóveis, requerem uma boa resolução, fiabilidade, baixa manutenção, baixo custo de produção e capacidade de trabalhar sob condições adversas. Devido a estes requisitos, os sensores mais utilizados são os magnéticos, indutivos e magneto-indutivos. Outro fator crítico é a dimensão do sensor, quanto mais reduzido e compacto, maior é o número de aplicações em que pode ser aplicado. No caso dos sensores magneto-indutivos e indutivos, uma forma de reduzir o seu tamanho é através do uso de a bobines planares impressas em placas de circuito impresso (PCB). Estas, para além de mais compactas, conseguem também reduzir os custos de produção, otimizar a repetibilidade e assemblagem, e permitir que o seu desenho seja facilmente adaptado às suas aplicações. No desenvolvimento de sensores indutivos, obter a indutância das bobinas, que funcionam como elemento transdutor, é essencial e desafiador no caso de bobinas planas. Atualmente, há duas abordagens no estado da arte: fórmulas de aproximação (para geometrias regulares), e simulações de modelos de elementos finitos (FEM). As simulações são demoradas e recorrem a ferramentas de software dispendiosas e que exigem muitos recursos computacionais. Esta tese tem como objetivo desenvolver uma ferramenta de cálculo analítico para obter a indutância de bobinas planas genéricas, reduzindo o tempo de desenvolvimento. A ferramenta possibilita ainda o cálculo da interferência que um alvo planar condutivo tem na indutância da bobine, tornando assim possível obter a resposta de um sensor indutivo baseado em eddy currents durante a sua fase de desenvolvimento. Esta tese, além de detalhar o desenvolvimento da ferramenta mencionada, também descreve todos os processos de validação implementados, através de simulações FEM e testes experimentais. A metodologia proposta foi aplicada com sucesso no desenvolvimento de um sensor de posição angular automotivo baseado em eddy currrents. Foi possível comprovar que a precisão da ferramenta desenvolvida está de acordo com as metodologias usualmente utilizadas, com a vantagem de ser mais rápida e económica.Angular sensors used in automotive applications require good precision, reliability, low maintenance, low production costs and the ability to work in harsh conditions. Due to these requirements, magnetic, inductive and magneto-inductive sensors are preferred and are used in current generations of automotive angular position sensors. The size of the sensors is another relevant factor in the development of new solutions. The smaller and more compact, the larger the number of applications in which they can be applied. In the case of magneto-inductive and inductive sensors, one way to reduce their size is to use planar coils printed on printed circuit boards (PCBs). These, in addition to occupy a smaller volume when compared to solenoids, also reduce production costs and optimize repeatability and simplify assembly. When developing inductive sensors, knowing the required inductance value of its coils is essential and this task can be challenging in the case of planar coils. Currently, two approaches are used to calculate the inductances of planar coils. When the coils have regular geometry approximation formulas are used, configuring some parameters. When they have irregular geometry or a more accurate result is desired, simulations using finite element methods (FEM) are chosen. These simulations have the disadvantage of being time-consuming, requiring expensive software applications and a huge computing resources. In view of the budget and the reduction of development time, this thesis provides an analytical calculation tool for the inductance of generic multi-layer planar coils. In this way, it is possible to develop dedicated applications in reduced time. The tool also allows to calculate the interference that a planar conductive target, of arbitrary geometry, can have on the coil inductance. Thus, it is possible to obtain the response of an inductive sensor based on eddy currents during its development phase. This thesis, in addition to detailing the development of the aforementioned tool, also describes all the validation processes implemented using FEM simulations and experimental tests. The proposed methodology was successfully applied in the development of an automotive angular position sensor based on eddy currents. It was possible to prove that the precision of the developed analytical tool is in concordance with the methodologies usually used, with the advantage of being faster and open source.Fundação para a Ciência e a Tecnologia (FCT) - bolsa de doutoramento PD/BD/128142/201

Advanced Sensors for Real-Time Monitoring Applications

It is impossible to imagine the modern world without sensors, or without real-time information about almost everything—from local temperature to material composition and health parameters. We sense, measure, and process data and act accordingly all the time. In fact, real-time monitoring and information is key to a successful business, an assistant in life-saving decisions that healthcare professionals make, and a tool in research that could revolutionize the future. To ensure that sensors address the rapidly developing needs of various areas of our lives and activities, scientists, researchers, manufacturers, and end-users have established an efficient dialogue so that the newest technological achievements in all aspects of real-time sensing can be implemented for the benefit of the wider community. This book documents some of the results of such a dialogue and reports on advances in sensors and sensor systems for existing and emerging real-time monitoring applications

Micro-manufactured Rogowski coils for fault detection of aircraft electrical wiring and interconnection systems (EWIS)

Aircraft wiring failures have increased over the last few years resulting in arc faults and high-energy flashover on the wiring bundle, which can propagate down through aircraft Electrical Wiring and Interconnect Systems (EWIS). It is considered cost prohibitive to completely rewire a plane in terms of man hours and operational time lost to do this, and most faults are only detectable whilst the aircraft is in flight. Temperature, humidity and vibration all accelerate ageing and failure effects on EWIS. This research investigates methods of in-situ non-invasive testing of aircraft wiring during fight. Failure Mode Effects and Analysis (FMEA) was performed on legacy aircraft EWIS using data obtained from RAF Brize Norton. Micro-Electro-mechanical- Systems (MEMS) were evaluated for use in a wire monitoring system that measures the environmental parameters responsible for ageing and failure of EWIS. Such MEMS can be developed into a Health and Usage Monitoring MicroSystem (HUMMS) by incorporating advanced signal processing and prognostic software. Current and humidity sensors were chosen for further investigation in this thesis. These sensors can be positioned inside and outside cable connectors of EWIS so that arc faults can be reliably detected and located. This thesis presents the design, manufacture and test of micro-manufactured Rogowski sensors. The manufactured sensors were benchmarked against commercial high frequency current transformers (HFCT), as these devices can also detect high frequency current signature due to wire insulation failure. Results indicate that these sensors possess superior voltage output compared to the HFCT. The design, manufacture and test of a polymer capacitive humidity sensor is also presented. Two different types of polymer were reviewed as part of the evaluation. A feature of the sensor design is recovery from exposure to chemicals found on wiring bundles. Current and humidity sensors were demonstrated to be suitable for integrating onto a common substrate with accelerometers, temperature sensors and pressure sensors for health monitoring and prognostics of aircraft EWIS.Engineering and Physical Sciences Research Council (EPSRC

Micro-manufactured Rogowski coils for fault detection of aircraft electrical wiring and interconnect systems (EWIS)

Aircraft wiring failures have increased over the last few years resulting in arc faults and high-energy flashover on the wiring bundle, which can propagate down through aircraft Electrical Wiring and Interconnect Systems (EWIS). It is considered cost prohibitive to completely rewire a plane in terms of man hours and operational time lost to do this, and most faults are only detectable whilst the aircraft is in flight. Temperature, humidity and vibration all accelerate ageing and failure effects on EWIS. This research investigates methods of in-situ non-invasive testing of aircraft wiring during fight. Failure Mode Effects and Analysis (FMEA) was performed on legacy aircraft EWIS using data obtained from RAF Brize Norton. Micro-Electro-mechanical- Systems (MEMS) were evaluated for use in a wire monitoring system that measures the environmental parameters responsible for ageing and failure of EWIS. Such MEMS can be developed into a Health and Usage Monitoring MicroSystem (HUMMS) by incorporating advanced signal processing and prognostic software. Current and humidity sensors were chosen for further investigation in this thesis. These sensors can be positioned inside and outside cable connectors of EWIS so that arc faults can be reliably detected and located. This thesis presents the design, manufacture and test of micro-manufactured Rogowski sensors. The manufactured sensors were benchmarked against commercial high frequency current transformers (HFCT), as these devices can also detect high frequency current signature due to wire insulation failure. Results indicate that these sensors possess superior voltage output compared to the HFCT. The design, manufacture and test of a polymer capacitive humidity sensor is also presented. Two different types of polymer were reviewed as part of the evaluation. A feature of the sensor design is recovery from exposure to chemicals found on wiring bundles. Current and humidity sensors were demonstrated to be suitable for integrating onto a common substrate with accelerometers, temperature sensors and pressure sensors for health monitoring and prognostics of aircraft EWIS

A Novel Power-Efficient Wireless Multi-channel Recording System for the Telemonitoring of Electroencephalography (EEG)

This research introduces the development of a novel EEG recording system that is modular, batteryless, and wireless (untethered) with the supporting theoretical foundation in wireless communications and related design elements and circuitry. Its modular construct overcomes the EEG scaling problem and makes it easier for reconfiguring the hardware design in terms of the number and placement of electrodes and type of standard EEG system contemplated for use. In this development, portability, lightweight, and applicability to other clinical applications that rely on EEG data are sought. Due to printer tolerance, the 3D printed cap consists of 61 electrode placements. This recording capacity can however extend from 21 (as in the international 10-20 systems) up to 61 EEG channels at sample rates ranging from 250 to 1000 Hz and the transfer of the raw EEG signal using a standard allocated frequency as a data carrier. The main objectives of this dissertation are to (1) eliminate the need for heavy mounted batteries, (2) overcome the requirement for bulky power systems, and (3) avoid the use of data cables to untether the EEG system from the subject for a more practical and less restrictive setting. Unpredictability and temporal variations of the EEG input make developing a battery-free and cable-free EEG reading device challenging. Professional high-quality and high-resolution analog front ends are required to capture non-stationary EEG signals at microvolt levels. The primary components of the proposed setup are the wireless power transmission unit, which consists of a power amplifier, highly efficient resonant-inductive link, rectification, regulation, and power management units, as well as the analog front end, which consists of an analog to digital converter, pre-amplification unit, filtering unit, host microprocessor, and the wireless communication unit. These must all be compatible with the rest of the system and must use the least amount of power possible while minimizing the presence of noise and the attenuation of the recorded signal A highly efficient resonant-inductive coupling link is developed to decrease power transmission dissipation. Magnetized materials were utilized to steer electromagnetic flux and decrease route and medium loss while transmitting the required energy with low dissipation. Signal pre-amplification is handled by the front-end active electrodes. Standard bio-amplifier design approaches are combined to accomplish this purpose, and a thorough investigation of the optimum ADC, microcontroller, and transceiver units has been carried out. We can minimize overall system weight and power consumption by employing battery-less and cable-free EEG readout system designs, consequently giving patients more comfort and freedom of movement. Similarly, the solutions are designed to match the performance of medical-grade equipment. The captured electrical impulses using the proposed setup can be stored for various uses, including classification, prediction, 3D source localization, and for monitoring and diagnosing different brain disorders. All the proposed designs and supporting mathematical derivations were validated through empirical and software-simulated experiments. Many of the proposed designs, including the 3D head cap, the wireless power transmission unit, and the pre-amplification unit, are already fabricated, and the schematic circuits and simulation results were based on Spice, Altium, and high-frequency structure simulator (HFSS) software. The fully integrated head cap to be fabricated would require embedding the active electrodes into the 3D headset and applying current technological advances to miniaturize some of the design elements developed in this dissertation