Analysis And Design Of Low Profile Multiband Multifunctional Antenna Arrays

Light-weight phased array antennas for aerospace and mobile applications require utilizing the same antenna aperture to provide multiple functions with dissimilar radiation pattern specifications (e.g., multiband operation for communications and tracking). Multi-functional antennas provide advantages over aggregate antenna clusters by reducing space requirements, and can aid in the optimal placement of all required apertures to provide adequate isolation between channels. Furthermore, the combination of antenna apertures into a comgeometry mitigates co-site installation issues by addressing interference within the integrated radiator design itself as opposed to the extensive analysis which is required to configure multiple radiators in close proximity. The combination of multiple radiators into a single aperture can only be achieved with the proper selection of antenna topology and accompanying feed network design. This research proposes a new technique for the design of multiband arrays in which a comaperture is used. Highlighted by this method is the integration of a tri-band array comprised of an x-band (12 ghz) microstrip patch array on a superstrate above printed dual-band (1 and 2 ghz) slot loop antenna arrays in an octave-spaced lattice. The selection of a ground backing reflector is considered for improved gain and system packaging, but restricts the utility of the design principally due to the î›/4 depth of the ground plane. Therefore, a novel multiband high impedance surfaces (his) is proposed to load the slot apertures for reduced height. The novel techniques proposed here will enable the design of a low profile and conformal single aperture supporting multi-band and multi-functional operations

1.45GHz-1.55GHz Tunable RF Band-pass Filter

RF signals are used in the communication field in general. It has special band called microwave band which is the focus of this project. The idea of filtering comes from the need to transmit certain frequency of ranges of interest and block others. In this project the focus is on tunable filters using MEMS idea to solve the problem of complexity and price of the conventional tunable filters. The project focuses on L band to get the range from 1.45GHz to 1.55 GHz. The project starts by designing the low pass prototype and convert it to comb-line filter to find the capacitance range for the design of the tuneable capacitor using CMOS-MEMS technology. The tunable capacitor has to be modelled and designed. Theoretical modelling and ADS simulation determined the tuning range required for the capacitor is from 1.72pF to 1.84pF. A CMOS-MEMS fixed and tuneable capacitors were designed and simulated to achieve this range of capacitance and requires a voltage of 20V for tuning. Thus the objectives of the study have been achieved successfully and recommendations are made to achieve a wider frequency range for the filter and for integration of the filter with the tunable capacitor

Development of a low-cost graphene-based impedance biosensor

PhD ThesisThe current applicability and accuracy of point-of-care devices is limited, with the need of future technologies to simultaneously target multiple analytes in complex human samples. Graphene’s discovery has provided a valuable opportunity towards the development of high performance biosensors. The quality and surface properties of graphene devices are critical for biosensing applications with a preferred low contact resistance interface between metal and graphene. However, each graphene production method currently results in inconsistent properties, quality and defects thus limiting its application towards mass production. Also, post-production processing, patterning and conventional lithography-based contact deposition negatively impact graphene properties due to chemical contamination. The work of this thesis focuses on the development of fully-functional, label-free graphene-based biosensors and a proof-of-concept was established for the detection of prostate specific antigen (PSA) in aqueous solution using graphene platforms. Extensive work was carried out to characterize different graphene family nanomaterials in order to understand their potential for biosensing applications. Two graphene materials, obtained via a laser reduction process, were selected for further investigations: reduced graphene oxide (rGO) and laser induced graphene from polyimide (LIG). Electrically conductive, porous and chemically active to an extent, these materials offer the advantage of simultaneous production and patterning as capacitive biosensing structures, i.e. interdigitated electrode arrays (IDE). Aiming to enhance the sensitivity of these biosensors, a novel, radio-frequency (RF) detection method was investigated and compared with conventional electrochemical impedance spectroscopy (EIS) on a well-known biocompatible material: gold (standard). It was shown that the RF detection methods require careful design and testing setup, with conventional EIS performing better in the given conditions. The method was further used on rGO and LIG IDE devices for the electrochemical impedance detection of PSA to assess the feasibility of the graphene based materials as biosensors. The graphene-based materials were successfully functionalized via the available carboxylic groups, using the EDC-NHS chemistry. Despite the difficulty of producing reproducible graphene-based electrodes, highly required for biosensor development, extensive testing was carried out to understand their feasibility. The calibration curves obtained via successive PSA addition showed a moderate-to-high ii sensitivity of both rGO and LIG IDE. However, further adsorption and drift testing underlined some major limitations in the case of LIG, due to its complex morphology and large porosity. To enable low contact resistance to these biosensors, the electroless nickel coating process is shown to be compatible with various graphene-based materials. This was demonstrated by tuning the chemical nickel bath and method conditions for pristine graphene and rGO for nickel contacts deposition

Utilisation of microsystems technology in radio frequency and microwave applications

The market trends of the rapidly growing communication systems require new product architectures and services that are only realisable by utilising technologies beyond that of planar integrated circuits. Microsystems technology (MST) is one such technology which can revolutionise radio frequency (RF) and microwave applications. This article discusses the enabling potential of the MST to meet the stringent requirements of modern communication systems. RF MST fabrication technologies and actuation mechanisms empower conventional processes by alleviating the substrate effects on passive devices and provide product designers with high quality versatile microscale components which can facilitate system integration and lead to novel architectures with enhanced robustness and reduced power consumption. An insight on the variety of components that can be fabricated using the MST is given, emphasizing their excellent electrical performance and versatility. Research issues that need to be addressed are also discussed. Finally, this article discusses the main approaches for integrating MST devices in RF and microwave applications together with the difficulties that need to be overcome in order to make such devices readily available for volume-production.peer-reviewe

The effect of bending on laser-cut electro-textile inductors and capacitors attached on denim as wearable structures

In this paper we present the design, fabrication and characterization of electro-textile inductor and capacitor patterns on denim fabric as a basis for the development of wearable e-textiles. Planar coil inductors have been harnessed as antenna structures for the development of Near Field Communication (NFC) tags with temperature sensing capability, while interdigitated electrode (IDE) capacitors have been used as humidity sensors for wearable applications. The effect of bending in the electrical performance of such structures was evaluated, showing variations below 5% in both inductance and capacitance values for bending angles in the range of interest, i.e. those fitting to human limbs. In the case of the fabricated NFC tags, a shift in the resonance frequency below 1.7% was found, meaning that the e-textile tag would still be readable by an NFC- enabled smartphone. In respect of the capacitive humidity sensor, we obtained a minimum capacitance variation of 40% for a relative humidity range from 10% to 90%. Measured thermal shift was below 5% in the range from 10 to 40oC. When compared to the 4% variation due to bending, it can be concluded that this capacitive structure can be harnessed as humidity sensor even under bending strain conditions and moderate temperature variations. The development and characterization of such structures on denim fabrics, which is one of the most popular fabrics for everyday clothing, combined with the additional advantage of affordable and easy fabrication methodologies, means a further step towards the next generation of smart e-textile products

On-Chip Power Supply Noise: Scaling, Suppression and Detection

Design metrics such as area, timing and power are generally considered as the primary criteria in the design of modern day circuits, however, the minimization of power supply noise, among other noise sources, is appreciably more important since not only can it cause a degradation in these parameters but can cause entire chips to fail. Ensuring the integrity of the power supply voltage in the power distribution network of a chip is therefore crucial to both building reliable circuits as well as preventing circuit performance degradation. Power supply noise concerns, predicted over two decades ago, continue to draw significant attention, and with present CMOS technology projected to keep on scaling, it is shown in this work that these issues are not expected to diminish. This research also considers the management and on-chip detection of power supply noise. There are various methods of managing power supply noise, with the use of decoupling capacitors being the most common technique for suppressing the noise. An in-depth analysis of decap structures including scaling effects is presented in this work with corroborating silicon results. The applicability of various decaps for given design constraints is provided. It is shown that MOS-metal hybrid structures can provide a significant increase in capacitance per unit area compared to traditional structures and will continue to be an important structure as technology continues to scale. Noise suppression by means of current shifting within the clock period of an ALU block is further shown to be an additional method of reducing the minimum voltage observed on its associated supply. A simple, and area and power efficient technique for on-chip supply noise detection is also proposed

A Pipe-Embeddable Impedance Sensor for Monitoring Water Leaks in Distribution Networks: Design and Validation

Water leakage is one of main problems of distribution infrastructures, reaching unacceptable peaks of 50% of water lost in old networks in several countries. In order to address this challenge, we present an impedance sensor able to detect small water leaks (below 1 L of released volume). The combination of real-time sensing and such a sensitivity allows for early warning and fast response. It relies on a set of robust longitudinal electrodes applied on the external surface of the pipe. The presence of water in the surrounding medium alters its impedance in a detectable way. We report detailed numerical simulations for the optimization of electrode geometry and sensing frequency (2 MHz), as well as the successful experimental proof in the laboratory of this approach for a pipe length of 45 cm. Moreover, we experimentally tested the dependence of the detected signal on the leak volume, temperature, and morphology of the soil. Finally, differential sensing is proposed and validated as a solution to reject drifts and spurious impedance variations due to environmental effects

Sensores de toque para electrónica automóvel impressa em 3D: análise, síntese, e aspectos de compatibilidade electromagnética

The Additive Manufacturing has been developing more and more, providing numerous advantages to the industry. Among such advantages is the use of materials with conductive properties combined with 3D printing techniques, which enables development of new devices embedded in plastic elements. One of the industries where Additive Manufacturing methods can be applied most successfully is the automotive industry. The electrification of cars, connected cars, autonomous driving, equipment enriched with sensors for better comfort are some of the challenges that this industry faces. Thus, innovation is made in the sense of developing new products to meet the presented challenges, always focusing on the user. Thus, this Master Thesis aims to study, explore and expand these concepts and apply them to the development of a touch sensor, as well as to understand what are the problems of compatibility and electromagnetic interference that can be encountered in automotive environment, specifically, in a smart door for a car. This work begins with the study of Additive Manufacturing methods, the types of measurements for a touch sensor, the sensor designs, and the electromagnetic compatibility and interference issues relevant for such sensors. Useful tools are developed to calculate the sensor capacitance, inductance and resonant frequency. Also, a script is developed to obtain the structural parameters for the resonant frequencies in desired ranges. These tools made it possible to develop a macro to automate creation of 3D structures in CST Studio Suite and thus to be able to simulate such structures for a large set of obtained parameters. Based on the simulations, we designed two sensor structures operating at the desired frequencies and, with the 3D structures ready, moved on to the experimental measurements, producing a PCB prototype for each structure. Thus, by completing these procedures it was concluded that the experimental measurements allowed us to test the developed tools and models and to validate the entire study.A Manufatura Aditiva tem vindo a desenvolver-se cada vez mais, proporcionando inúmeras vantagens à indústria. Dentro delas a utilização de um material com propriedades condutoras e aliado a técnicas de impressão 3D, permite desenvolver novos dispositivos embutidos/incorporados numa peça de plástico. Uma das indústrias que mais se pode aplicar métodos de Manufatura Aditiva é a indústria automóvel. A eletrificação dos automóveis, os carros conetados, condução autónoma, a sonorização dos equipamentos e o conforto são alguns dos desafios que esta indústria enfrenta. Assim, a inovação faz-se no sentido de desenvolvimento de produtos para responder aos desafios apresentados, sempre com o foco no utilizador. Assim, esta Dissertação de Mestrado tem como objetivo estudar, explorar e expandir estes conceitos e aplicá-los ao desenvolvimento de um sensor de toque, além de perceber quais os problemas de compatibilidade e interferências eletromagnéticas num ambiente automóvel, mais concretamente numa porta inteligente para um carro. O trabalho iniciou-se com o estudo dos métodos de Manufatura Aditiva, tipos de medidas para um sensor de toque, design, compatibilidade e interferência eletromagnética destes sensores. Desenvolveram-se ferramentas para auxílio dos cálculos de capacitância, indutância e frequência de ressonância. Também se elaborou um script para obtenção dos parâmetros das frequências de ressonância nas gamas desejadas. Estas ferramentas possibilitaram o desenvolvimento de uma macro para criar as estruturas 3D num simulador e, assim, poder simular os parâmetros obtidos. Com as simulações alcançaram-se duas estruturas nas frequências desejadas e com as estruturas 3D criadas passámos à medição experimental, produzindo uma Printed Circuit Board (PCB) para cada estrutura. Assim, com estes processos, concluiu-se que as nossas medições experimentais permitem validar as ferramentas desenvolvidas, assim como todo o estudo e teoria desenvolvida.Mestrado em Engenharia Eletrónica e Telecomunicaçõe

A Reconfigurable Pseudohairpin Filter Based on MEMS Switches

This work presents a bandpass-reconfigurable planar pseudohairpin filter based on RF-MEMS switches. Hairpin-line structures are preferred to design microstrip filters because this class of filters offers a more compact size, and, in general, hairpin filters do not need ground connections for resonators. In this work, the U-shape resonators are arranged to obtain an interdigit capacitor to improve the coupling between the resonators. RF-MEMS switches modify the lengths of coupled resonators by adding microstrip segments to control the filter bandwidth, moving the center frequency and the return loss. An experimental hairpin tunable filter prototype based on RF-MEMS has been designed, fabricated, numerically and experimentally assessed, and compared concerning its tunability, quality factor, and capability with standard tunable filters based on PIN diodes. In conclusion, the tunable hairpin filter based on RF-MEMS switches offers the best performance in center frequency tuning range, compactness, and power consumption regarding reconfigurable filters based on standard PIN diodes switches. The obtained results are appealing and demonstrate the capabilities and potentialities of RF-MEMS to operate with the new communication standards that work at high microwave frequency bands