| 1. |
- Amin, Yasar
(författare)
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Printable Green RFID Antennas for Embedded Sensors
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the recent years, radio-frequency identification (RFID) technology has been widely integrated into modern society applications, ranging from barcode successor to retail supply chain, remote monitoring, detection and healthcare, for instance. In general, an RFID tag or transponder is composed of an antenna and an application-specific integrated circuit chip. In a passive UHF RFID system (which is the focus of presented research), the communication between the transponder tag and the reader is established by modulating the radar cross section (RCS) of the transponder tag. The need for flexible RFID tags has recently been increased enormously; particularly the RFID tags for the UHF band ensure the widest use but in the meantime face considerable challenges of cost, reliability and environmental friendliness.The multidimensional focus of the aforementioned research encompasses the production of low-cost and reliable RFID tags. The state-of-the-art fabrication methods and materials for proposed antennas are evaluated in order to surmount the hurdles for realization of flexible green electronics. Moreover, this work addresses the new rising issues interrelated to the field of economic and eco-friendly tags comprising of paper substrate. Paper substrates offer numerous advantages for manufacturing RFID tags, not only is paper extensively available, and inexpensive; it is lightweight, recyclable and can be rolled or folded into 3D configurations.The most important aspect of an RFID system's performance is the reading range. In this research several pivotal challenges for item-level tagging, are resolved by evolving novel structures of progressive meander line, quadrate bowtie and rounded corner bowtie antennas in order to maximize the reading distance with a prior selected microchip under the various constraints (such as limited antenna size, specific antenna impedance, radiation pattern requirements). This approach is rigorously evolved for the realization of innovative RFID tag antenna which has incorporated humidity sensor functionality along with calibration mechanism due to distinctiveness of its structural behavior which will be an optimal choice for future ubiquitous wireless sensor network (WSN) modules.The RFID market has grown in a two-dimensional trend, one side constitutes standalone RFID systems. On the other side, more ultramodern approach is paving its way, in which RFID needs to be integrated with broad operational array of distinct applications for performing different functions including sensors, navigation, broadcasting, and personal communication, to mention a few. Using different antennas to include all communication bands is a straightforward approach, but at the same time, it leads to increase cost, weight, more surface area for installation, and above all electromagnetic compatibility issues. The indicated predicament is solved by realization of proposed single wideband planar spirals and sinuous antennas which covers several bands from 0.8-3.0GHz. These antennas exhibit exceptional performance throughout the operational range of significance, thus paving the way for developing eco-friendly multi-module RF industrial solutions.
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| 2. |
- Ahmad, Jawad, 1985-
(författare)
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Development and Characterization of Large Area Pressure Sensors and Sitting Posture Monitoring Systems
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- With the emergence of the Internet and rapid development of science and technology over the past few decades, many individuals worldwide now rely on the Internet to conduct daily activities ranging from education, business and creativity to communication and shopping. As we tend to spend more and more time on the Internet and engage less in physical activities, this persistent behaviour could result in some health-related issues within a relatively short period of time. This behaviour, known as sedentary lifestyle, may be related to a higher risk of cardiovascular disease, osteoporosis, obesity, anxiety, pressure ulcers and many other illnesses. As a consequence, there has been great interest in developing non-invasive and unobtrusive measurement techniques for a variety of health care-monitoring applications, such as for blood oxygen saturation, stress levels, electrocardiograms and glucose monitoring. In such systems, wearable and flexible electronics technologies may enable monitoring of vital signs, offering significant potential for early screening as well as long-term behaviour modelling.In this thesis, large area pressure sensors based on non-conventional materials are proposed and realised by screen printing technique for monitoring sitting postures. The developed pressure sensing system measures distributed pressure when an individual sits on a chair equipped with a pressure sensor array. This technology could provide grounding for the advancement of health-related monitoring systems for both able-bodied and disabled individuals and inform them of their sitting time and sitting posture, and this could be used to establish a sitting pattern. To accomplish this, pressure sensors have been designed using non-conventional flexible electronics. A blend of non-conductive and low-resistance ink is used as pressure-sensitive material to enable the realization of screen-printed sensors. To characterise the performance of the suggested pressure sensor, several tests, such as repeatability, drift and flexibility, are conducted. The sensor has also been exposed to different humidity and temperature conditions in a climate chamber to examine its functionalities.A graphical user interface was developed for real-time demonstration of data from distributed pressure points in the form of a pressure map to display the pressure values. Four sitting postures are identified: forward, backward, left, and right leaning. Furthermore, a stretchable pressure sensor is proposed that could follow slight stretching with regard to changes in the shape of the human skin. Machine learning algorithms have been employed to further enhance the sitting posture identification, and accuracy of 99.03% is attained. A standalone embedded system capable of illustrating real-time pressure data has been developed with the potential to be used in portable health monitoring systems. In summary, this work provides a promising framework for measuring pressure distribution and identifying irregular sitting postures that may help to reduce the potential risks of developing health-related issues associated with prolonged sitting time.
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| 3. |
- Li, Xiaotian
(författare)
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Towards Large-Area Electronic Systems Using Non-Conventional Substrate and Conductor Materials
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Flexible circuits, also known as flexible printed circuit boards, were originally developed in the 1950s for interconnection between multiple electronic devices when flexibility and movement were required. Nowadays, flexible circuits can be used for implementing electronic systems much more complicated than just interconnections. A commonly seen material combination of flexible circuits is copper foils laminated on polyimide substrates, although these solutions are both expensive and environmentally hazardous. With developments in printed electronics, many non-conventional materials can be used in fabricating flexible circuits that have advantages such as increased flexibility, low cost, a small environmental impact, etc. In addition, fast and efficient manufacturing methods can produce flexible electronics in large volumes. This opens a window of opportunity to create electronic systems over geometrically large areas. This thesis proposes methods and guidelines for how to implement largearea electronic devices using non-conventional flexible materials and technologies. The thesis specifically focuses on electronic systems that integrate both digital and analogue signals. Further, it demonstrates and provides examples of how signals in the microwave frequencies, commonly requiring expensive materials, can be handled with non-conventional materials and technologies. Several conductor-substrate material combinations are used, which are fabricated using industrial processes. The conductor materials include conductive inks, copper foils, and aluminium foils, while the substrate materials comprise papers, a nonwoven fabric, and a polyimide. In particular, methods are investigated in order to achieve a low DC resistance in printed conductiveink-based tracks, which opens the possibilities for them to be used in highcurrent applications. Several surface mounting techniques are developed for incorporating surface mount devices within the fabricated flexible circuits, including the use of low-temperature solder paste, isotropic conductive adhesives, and anisotropic conductive adhesives. Some of the techniques have achieved sufficiently low contact resistance and adequate component bonding strengths, and thus can be used in implementing hybrid electronic systems. In addition, most of the techniques have the potential to be used in automated component assembly lines. As demonstrators, two antenna systems for commercial RFID readers operating at high frequency (13.56 MHz) and ultra-high frequency (867 MHz) iv Abstract bands are implemented, which comprise both digital and analogue signals. The two antenna systems are designed as part of SP4T switching networks using standard antenna elements as the loads of the network. It is shown in the results that both antenna systems have low RF attenuations, the potential to perform passive RFID tag positioning, and the possibility to be expanded to larger areas. Based on the characterisations to the two antenna systems, discussions are made about how large the antenna system areas can be as well as how many antenna elements can be achieved in a single antenna system. This thesis provides a material-to-system approach and demonstrates that non-conventional flexible materials and printed electronic technologies are suitable choices for large-area electronics.
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