| 1. |
- 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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| 2. |
- Persson, Johan, et al.
(författare)
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Geometrical Optimization of Jetting Duct
- 2020
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Ingår i: 2020 8th International Electrical Engineering Congress (iEECON). - : IEEE. - 9781728130767 ; , s. 1-3
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Konferensbidrag (refereegranskat)abstract
- This paper presents and evaluates three new designs of fibre optic cable ducts for jetting. The three designs are longitudinal ridges with square, triangular and semicircular geometries. The effects of the geometries are evaluated with regards to electrostatic force, fluid drag force and jetting length with limited push force. An optimal design is suggested, with triangular longitudinal ridges on the inner surface of the duct.
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| 3. |
- Akram, Shazad, et al.
(författare)
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Design and Development of a Battery Powered Electrofusion Welding System for Optical Fiber Microducts
- 2020
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Ingår i: IEEE Access. - 2169-3536. ; 8, s. 173024-173043
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Tidskriftsartikel (refereegranskat)abstract
- At present, optical fiber microducts are coupled together by mechanical types of joints. Mechanical joints are thick, require a large space, and reduce the installation distance in multi-microduct installation. They may leak or explode in the blown fiber installation process. Mechanical joints are subjected to time dependent deterioration under long service times beneath the earth's surface. It may start with a small leakage, followed by damage due to water freezing inside the optical fiber microduct. Optical fiber microducts are made up of high-density polyethylene, which is considered most suitable for thermoelectric welding. For thermoelectric welding of two optical fiber microducts, the welding time should be one second, and should not cause any damage to the inner structure of the microducts that are being coupled. To fulfill these requirements, an LTspice simulation model for the welding system was developed and validated. The developed LTspice model has two parts. The first part models the power input to joule heating wire and the second part models the heat propagation inside the different layers of the optical fiber microduct and surrounding joint by using electro-thermal analogy. In order to validate the simulation results, a battery powered prototype welding system was developed and tested. The prototype welding system consists of a custom-built electrofusion joint and a controller board. A 40 volt 4 ampere-hour Li-Ion battery was used to power the complete system. The power drawn from the battery was controlled by charging and discharging of a capacitor bank, which makes sure that the battery is not overloaded. After successful welding, a pull strength test and an air pressure leakage test were performed to ensure that the welded joints met the requirements set by the mechanical joints. The results show that this new kind of joint and welding system can effectively replace mechanical joints in future optical fiber duct installations.
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| 4. |
- Bakar, Muhammad Abu, 1969-
(författare)
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Wide Range Isolated Power Converters
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Power electronics technology is rapidly growing in most industrialapplications. There is an increasing demand for efficient and low profilepower converters in the industry like automotive, power grids, renewableenergy systems, electric rail systems, home appliances, and informationtechnology. In some applications, there is an increasing demand for powerconverters showing a stable performance over a wide variation in inputvoltage, whereas in others the demand is for converters showing a stableperformance over a wide variation of output voltage. In this regard, not somuch work has been done to combine both requirements into one solution;this is the primary focus of the dissertation. It presents a unique solution tothe industry, which addresses both requirements. The technique can beapplied in a one size fits all solution which not only extends the range of theline voltage and the output voltage but also provides the flexibility to adjustthe required set of line/output voltage. The variation in line voltage severelydegrades the performance of power converters because of the extendedfreewheeling interval, more circulating current, narrow range of zero voltageswitching and increased EMI. To overcome this, the converter consists of tworeconfigurable modes on the input side that can be configured following thevariation in line voltage to maintain a stable performance. In addition, itproposes three reconfigurable steps for the output voltage, which can be usedto adjust the output voltage from base level X to 2X and 4X in discrete stepsand/or from X - 4X volt while showing stable performance. This makes theproposal a 2x3 reconfigurable modes power converter, which means that thegain of the proposed converter can be raised to 4 or 8. Furthermore, theflexibility in the reconfigurable structure simplifies the implementation of theproposed single solution in a range of applications. Each concept proposed inthe thesis is verified analytically, experimentally and modelling it into aSPICE simulation. Then the whole concept is confined into a single entity,which is applied in an example application of a phase shifted full bridgeconverter. The full converter is characterized for input voltage 100-400Vdc, theoutput voltage 24-96Vdc, and up to the load power of 1kW.
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| 5. |
- Du, Yijun, et al.
(författare)
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Design of ultra-wideband antenna with high-selectivity band notches using fragment-type etch pattern
- 2020
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Ingår i: Microwave and optical technology letters (Print). - : Wiley. - 0895-2477 .- 1098-2760. ; 62:2, s. 912-918
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Tidskriftsartikel (refereegranskat)abstract
- By specifying objective functions defining the two bands to be notched with high roll-off criteria (ROCs), optimization searching for the best fragment-type etch pattern on ultra-wideband (UWB) antenna is implemented by using multi-objective optimization. The optimization with too many objective functions requires special treatment to improve the searching efficiency. In this design, two slits are preset on appropriate positions on different sides of the UWB radiator to constrain the decision space for etch pattern searching and yield two initial notched bands to speed up the optimization. For demonstration, a UWB patch antenna is designed with dual-band notches of ROC = 0.63 at WiMAX band and ROC = 0.65 at WLAN band. Both the simulation and measurement results indicate that there is significant improvement of the selectivity of the dual-band notches.
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