| 1. |
- Nilsson, Joakim, 1989-
(författare)
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Wireless High-Temperature Monitoring of Power Semiconductors : A Single-Chip Approach
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Because failures in power electronic equipment can cause production stops and unnecessary damage to interconnected equipment, monitoring schemes that are able to predict such failures provide various economic and safety benefits. The primary motivation for this thesis is that such monitoring schemes can increase the reliability of energy production plants. Power semiconductors are crucial components in power electronic equipment, and monitoring their temperatures yields information that can be used to predict emerging failures.This thesis presents a system concept for wireless, single-chip, high-temperature monitoring of power semiconductors. A wireless single-chip solution is both cost effective and easy to integrate with existing power semiconductor modules. However, the concept presents two major challenges: the implementation of wireless power and communication, and the low-power design of the temperature sensors. To address these challenges, the feasibility of using on-chip coils to provide communication with and to obtain power from an external reader coil is demonstrated, and a low-power, high-temperature bandgap temperature sensor is developed.For the challenge of generating geometries of on-chip coils with high power transfer efficiencies, a gradient ascent algorithm is used to generate geometries that provide high power transfer efficiency at the frequency of interest. A theory is developed, focused on the relation between optimised coil geometries and the load requirements of an application. A cutoff-point is discovered, beyond which power delivered to the load does not increase even if the load is made lighter. Electromagnetic simulations for an on-chip coil model are presented, which show that this load-limit lies around 10 kΩ for one 350 nM process. The model is verified with measurements on manufactured devices.To generate coils which operate within a desired frequency band in which sufficient radiated energy is permitted, a methodology for tuning on-chip coils with on-chip fuses is presented. The decision to use fuses for tuning instead of transistors for this application is due a transistor's requirement of a DC supply for bias. For wireless single-chip systems, no such DC supply is available at system start-up. The methodology presented addresses the challenge of achieving high Q~factors for capacitor-fuse series connections despite the fact the fuse resistance of on-chip fuses is finite in their blown state and non-zero in their active state.A single-chip, on-chip coil solution comes with advantages such as galvanic isolation from the power device and simplicity of integration in existing modules. However, because a wireless design with a small on-chip coil will limit the amount of available power, it incurs the disadvantage of requiring a low-power design for the temperature sensor. Therefore, a design is presented of a temperature sensor consuming power in the microwatt range in the high-temperature region where it is useful for detecting incipient faults, particularly solder faults. This is achieved by compensating for leakage currents that arise in hot reverse-biased p-n junctions, which become significant at these temperatures.At high temperatures, these leakage currents can approach or even surpass the level of a circuit's quiescent current. Earlier work on leakage current compensation techniques is examined, compared to and combined with a compensation technique designed to compensate for collector-base leakage in the main bipolar pair of a Brokaw bandgap reference. Experiments show that fully analogue sensors operating at up to at least 230 °C for a sensitivity of 2 mV/°C are feasible at a power consumption around 10 µW. Such sensors would yield a resolution of 2 °C if an 8-bit analogue-to-digital converter is employed. However, the transmission of data to the transmitter coil remains future work. Furthermore, a discussion is held to address design of unimplemented system components which are needed in order to implement a complete single-chip temperature measurement system. Points discussed include high-temperature analogue-to-digital conversion, clock generation and wireless communication.
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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. |
- Ahmad, Jawad, 1985-, et al.
(författare)
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A Proposal of Implementation of Sitting Posture Monitoring System for Wheelchair Utilizing Machine Learning Methods
- 2021
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Ingår i: Sensors. - : MDPI. - 1424-8220. ; 21
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a posture recognition system aimed at detecting sitting postures of a wheelchair user. The main goals of the proposed system are to identify and inform irregular and improper posture to prevent sitting-related health issues such as pressure ulcers, with the potential that it could also be used for individuals without mobility issues. In the proposed monitoring system, an array of 16 screen printed pressure sensor units was employed to obtain pressure data, which are sampled and processed in real-time using read-out electronics. The posture recognition was performed for four sitting positions: right-, left-, forward- and backward leaning based on k-nearest neighbors (k-NN), support vector machines (SVM), random forest (RF), decision tree (DT) and LightGBM machine learning algorithms. As a result, a posture classification accuracy of up to 99.03 percent can be achieved. Experimental studies illustrate that the system can provide real-time pressure distribution value in the form of a pressure map on a standard PC and also on a raspberry pi system equipped with a touchscreen monitor. The stored pressure distribution data can later be shared with healthcare professionals so that abnormalities in sitting patterns can be identified by employing a post-processing unit. The proposed system could be used for risk assessments related to pressure ulcers. It may be served as a benchmark by recording and identifying individuals’ sitting patterns and the possibility of being realized as a lightweight portable health monitoring device.
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| 4. |
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| 5. |
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| 6. |
- 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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| 7. |
- Ahmad, Jawad, 1985-
(författare)
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Screen Printed Large Area Sensors for Pressure Distribution Monitoring in Wheelchairs
- 2019
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A sedentary lifestyle can induce health related problems including pressure ulcers. Prolonged sitting inadequacies constitute a risk for pressure ulcer to many individuals, in particular people with disabilities and reduced mobility. The measurement of distributed pressure and detection of irregular sitting postures are essential in prevention of the risk of developing pressure ulcers.In this thesis, a screen-printed pressure sensor for a large area is presented, with the objective of measuring the distributed pressure of a seated person in a wheelchair. The conductors and interdigital patterns are printed with silver-based ink. A blend of a non-conductive and a low resistive ink is used for customized resistance for an optimal sensing range of the pressure sensor. The effect of moisture and temperature are realized in an environment chamber. For characterization, other key performance tests such as repeatability, drift and flexibility are carried out. The surface morphology is carried out for structural analysis of printed samples. The sensor data is acquired and processed using an 8-bit ATmega-2560 microcontroller and wirelessly transmitted to a PC for post-processing, storage and analysis. For real-time data presentation of distributed pressure points, a GUI has been developed to display the values obtained from the large area sensor. The detection of four sitting postures; forward leaning, backward leaning, left leaning and right leaning along with a normal sitting posture is attained. An analysis for stretchable printed tracks has been conducted to investigate the changes in electrical resistance using elongation tests, surface morphology and EDS. The optimal curing time and temperature were investigated to manufacture stretchable conductive tracks.In summary, the contributions in this thesis provides an effective approach regarding pressure distribution measurement and recognizing irregular sitting postures for wheelchair users.
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| 8. |
- Ahmad, Jawad, 1985-, et al.
(författare)
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Screen Printed Piezoresistive Sensors for Monitoring Pressure Distribution in Wheelchair
- 2019
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Ingår i: IEEE Sensors Journal. - : IEEE. - 1530-437X .- 1558-1748. ; 19:6, s. 2055-2063
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Tidskriftsartikel (refereegranskat)abstract
- Prolonged sitting inadequacies cause pressure ulcer to many individuals, especially to disadvantaged with reduced mobility. The measurement of distributed pressure and detection of irregular sitting postures is essential for preventing the risk of developing pressure ulcer. In this paper, a pressure sensing system capable of recognizing sitting postures by means of measuring interface pressure through printed pressure sensors is presented. A thin and flexible large area sensor is screen-printed using silver flake and carbon particle inks and comprises 16 sensing elements. For the evaluation of practical usability, the sensor characterization is carried out by conducting stability, repeatability, drift and bending tests. The performance of the sensor is checked under varying environmental conditions. Sitting posture detection accuracy above 80 % is achieved using a classification algorithm for four different sitting postures. Pressure distribution is monitored at a scanning rate of 10 Hz. A low power and small form factor of read-out electronics enables a compact packaging inside the seat cushion. The presented sensor design targets smart wheelchairs, but it is extendable to much larger areas, for example to be used in beds. The proposed sensing system would be of a great assistance for caregivers and health professionals.
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| 9. |
- Ahmad, Jawad, 1985-, et al.
(författare)
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Sitting Posture Recognition using Screen Printed Large Area Pressure Sensors
- 2017
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Ingår i: Proceedings of IEEE Sensors. - : IEEE. - 9781509010127 ; , s. 232-234
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Konferensbidrag (refereegranskat)abstract
- In the biomedical sector, pressure sensors exhibit an important role towards monitoring and recognition of sitting posture for wheelchair users, which is helpful for pressure ulcer prevention and cure. In this paper, a flexible and inexpensive screen printed large area pressure sensing system is presented. The large area sensor comprise three layers, is able to cancel-out false pressure detection, and achieves a sitting classification accuracy over 80 percent. The sensor matrix contains 16 sensors distributed over an area of 23.5 cm × 21.5 cm and the pressure points are monitored at a scanning rate of 77 Hz. The sensor system provides wireless communication and a Windows based GUI is developed that allows real-time presentation of pressure data by means of a pressure map. The presented sensor design targets smart wheelchairs but is suitable for any low cost and high throughput pressure distribution monitoring systems.
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| 10. |
- Ahmad, Jawad, 1985-, et al.
(författare)
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Stretchable Pressure Sensor Using Thermoplastic Polyurethane and Conductive Inks
- 2021
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Ingår i: Proceedings of IEEE Sensors. - : IEEE. - 9781728195018
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Konferensbidrag (refereegranskat)abstract
- The development of wearable health devices is an emerging technology, and pressure sensors have been widely used in several of these applications. Plenty of research within pressure sensors is focused on tactile sensing and artificial skin. In this paper, a highly flexible and stretchable pressure sensor is presented. The sensor comprises stretchable thermoplastic polyurethane (TPU) film as substrate and stretchable conductive inks as electrodes and sensing material. Screen printing is used to fabricate electrodes and pressure sensing components on TPU sheets. Electrical and mechanical properties of the fabricated sensors indicate good mechanical and electrical stability while retaining pressure sensing properties and marginal deterioration even after 100 elongation cycles. The findings show that the presented stretchable pressure sensor has a great potential for usage on surfaces where bending and stretching will occur while retaining nearly all of its electrical and mechanical capabilities. The proposed sensor may be employed as a wearable device to detect human movements.
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| 11. |
- Akram, Shazad, et al.
(författare)
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Battery powered inductive welding system for electrofusion joints in optical fiber microducts
- 2021
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Ingår i: Electronics. - : MDPI AG. - 2079-9292. ; 10:6
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Tidskriftsartikel (refereegranskat)abstract
- Optical fiber microducts are joined together by mechanical joints. These mechanical joints are bulky, require more space per joint, and are prone to air pressure leakage and water seepage during service. A battery powered electrofusion welding system with a resistive-type joint has been recently developed to replace mechanical joints. These resistive-type electrofusion joints require physical connectors for power input. Due to a different installation environment, the power input connectors of resistive optical fiber microduct joints may corrode over time. This corrosion of connectors will eventually cause water seepage or air pressure leakage in the long run. Moreover, due to connector corrosion, resistive-type optical fiber microduct joints cannot be re-heated in future if the need arises. In this study, an inductively coupled electrofusion-type joint was proposed and investigated. This inductive-type electrofusion joint is not prone to long-term corrosion risk, due to the absence of power connectors. Inductive-type electrofusion joints can be re-heated again for resealing or removal in the long run, as no metal part is exposed to the environment. The battery powered inductive welding system can be easily powered with a 38 volts 160 watt-hour battery. The inductive-type electrofusion joint was welded within one second, and passed a 300-newton pull strength test and a 10-bar air pressure leakage test. It was demonstrated that the power input requirement for inductive electrofusion joints is 64% higher than that of resistive electrofusion joints. However, these inductive joints are relatively easy to manufacture, inexpensive, have no air leakage, and no water seepage risk in highly corrosive environments.
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| 12. |
- Akram, Shazad, et al.
(författare)
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Capacitive and optical sensing for automatic detection and characterization of cleaning sponges in fiber optic microduct installations
- 2019
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Ingår i: Proceedings - 2019 8th International Workshop on Advances in Sensors and Interfaces, IWASI 2019. - : IEEE. - 9781728105574 ; , s. 274-278
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Konferensbidrag (refereegranskat)abstract
- Optical fiber duct installation requires blowing of cleaning sponges for dirt and moisture removal before blowing the fiber cables. The traditional method requires one operator that blows the sponge and one operator in the receiving end that manually evaluate the sponges until a dry sponge is received. The proposed system eliminates the need of a second operator by introducing a solution for automatic sponge detection and characterization of moisture in sponges at the receiving end. An optical sensor is used for detection and a capacitive sensor is developed to measure the sponge's wetness. Sensor data is automatically transmitted back to the operator at the feeding end via a mobile phone. The system is characterized to work with sponges ranging from saturated with wetness to what is deemed as dry.
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| 13. |
- 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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| 14. |
- Akram, Shazad, et al.
(författare)
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LTspice electro-thermal model of joule heating in high density polyethylene optical fiber microducts
- 2019
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Ingår i: Electronics. - : MDPI AG. - 2079-9292. ; 8:12
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Tidskriftsartikel (refereegranskat)abstract
- At present, optical fiber microducts are joined together by mechanical type joints. Mechanical joints are bulky, require more space in multiple duct installations, and have poor water sealing capability. Optical fiber microducts are made of high-density polyethylene which is considered best for welding by remelting. Mechanical joints can be replaced with welded joints if the outer surface layer of the optical fiber microduct is remelted within one second and without thermal damage to the inner surface of the optical fiber duct. To fulfill these requirements, an electro-thermal model of Joule heat generation using a copper coil and heat propagation inside different layers of optical fiber microducts was developed and validated. The electro-thermal model is based on electro-thermal analogy that uses the electrical equivalent to thermal parameters. Depending upon the geometric shape and material properties of the high-density polyethylene, low-density polyethylene, and copper coil, the thermal resistance and thermal capacitance values were calculated and connected to the Cauer RC-ladder configuration. The power input to Joule heating coil and thermal convection resistance to surrounding air were also calculated and modelled. The calculated thermal model was then simulated in LTspice, and real measurements with 50 µm K-type thermocouples were conducted to check the validity of the model. Due to the non-linear transient thermal behavior of polyethylene and variations in the convection resistance values, the calculated thermal model was then optimized for best curve fitting. Optimizations were conducted for convection resistance and the power input model only. The calculated thermal parameters of the polyethylene layers were kept intact to preserve the thermal model to physical structure relationship. Simulation of the optimized electro-thermal model and actual measurements showed to be in good agreement.
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| 15. |
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| 16. |
- Andersson, Henrik, et al.
(författare)
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Assembling surface mounted components on ink-jet printed double sided paper circuit board
- 2014
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 25:9
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Tidskriftsartikel (refereegranskat)abstract
- Printed electronics is a rapidly developing field where many components can already be manufactured on flexible substrates by printing or by other high speed manufacturing methods. However, the functionality of even the most inexpensive microcontroller or other integrated circuit is, at the present time and for the foreseeable future, out of reach by means of fully printed components. Therefore, it is of interest to investigate hybrid printed electronics, where regular electrical components are mounted on flexible substrates to achieve high functionality at a low cost. Moreover, the use of paper as a substrate for printed electronics is of growing interest because it is an environmentally friendly and renewable material and is, additionally, the main material used for many packages in which electronics functionalities could be integrated. One of the challenges for such hybrid printed electronics is the mounting of the components and the interconnection between layers on flexible substrates with printed conductive tracks that should provide as low a resistance as possible while still being able to be used in a high speed manufacturing process. In this article, several conductive adhesives are evaluated as well as soldering for mounting surface mounted components on a paper circuit board with ink-jet printed tracks and, in addition, a double sided Arduino compatible circuit board is manufactured and programmed.
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| 17. |
- Andersson, Henrik, et al.
(författare)
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Chemically programmed ink-jet printed resistive WORM memory array and readout circuit
- 2014
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Ingår i: Materials Research Express. - : Institute of Physics (IOP). - 2053-1591. ; 1:3, s. 035021-
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Tidskriftsartikel (refereegranskat)abstract
- In this paper an ink-jet printed write once read many (WORM) resistive memory fabricated on paper substrate is presented. The memory elements are programmed for different resistance states by printing triethylene glycol monoethyl ether on the substrate before the actual memory element is printed using silver nano particle ink. The resistance is thus able to be set to a broad range of values without changing the geometry of the elements. A memory card consisting of 16 elements is manufactured for which the elements are each programmed to one of four defined logic levels, providing a total of 4294 967 296 unique possible combinations. Using a readout circuit, originally developed for resistive sensors to avoid crosstalk between elements, a memory card reader is manufactured that is able to read the values of the memory card and transfer the data to a PC. Such printed memory cards can be used in various applications.
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| 18. |
- Andersson, Henrik, et al.
(författare)
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Investigation of Humidity Sensor Effect in Silver Nanoparticle Ink Sensors Printed on Paper
- 2014
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Ingår i: IEEE Sensors Journal. - 1530-437X .- 1558-1748. ; 14:3, s. Art. no. 6615915-
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Tidskriftsartikel (refereegranskat)abstract
- Thin inkjet-printed tracks of silver nanoparticles have previously been observed to show a non-reversible decrease in resistance when exposed to a high degree of relative humidity and thus providing sensor functionality with a memory effect. This paper provides a more in-depth explanation of the observed humidity sensor effect that originates from inkjet-printed silver nanoparticle sensors on a paper substrate. It is shown that the geometry of the sensor has a large effect on the sensor's initial resistance, and therefore also on the sensor's resistive dynamic range. The importance of the sensor geometry is believed to be due to the amount of solvent from the ink interacting with the coating of the paper substrate, which in turn enables the diffusion of salts from the paper coating into the ink and thus affecting the silver ink.
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| 19. |
- Andersson, Henrik, et al.
(författare)
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Modified EAS Tag Used as a Resistive Sensor Platform
- 2012
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Ingår i: Electronics. - : MDPI AG. - 2079-9292. ; 1:2, s. 32-46
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Tidskriftsartikel (refereegranskat)abstract
- In this article, a modified design of an RF Radio Frequency Electronic ArticleSurveillance (EAS) tag, used as a sensor platform, is manufactured and characterized. EAStags are passive devices consisting of a capacitor and coil, tuned to a resonance frequencyreadable by the detector equipment, in this case 8.2 MHz. They were originally used todetect whether merchandise was being moved through the detection gates at shop exits, inwhich case an alarm was triggered. If the capacitance is divided in two and a resistivesensor device inserted in between, the resonant Inductor-Capacitor (LC) circuit becomes anInductor-Capacitor-Capacitor-Resistor LCCR circuit and can be used as a sensor tag. Ahigh sensor resistance means that one capacitor is decoupled, leading to one resonancefrequency, while a low resistance will couple both capacitances into the circuit, resulting ina lower resonance frequency. Different types of resistive sensors exist that are able todetect properties such as pressure, moisture, light and temperature. The tag is manufacturedin Aluminum foil on a polyetylentereftalat (PET) substrate, resulting in a cost effectiveRF-platform for various resistive sensors. Two types of tags are designed andmanufactured, one with parallel plate capacitors and the other with interdigital capacitors.To test the tags, a resistive tilt sensor is mounted and the tags are characterized using anetwork analyzer. It is shown that for high resistance, the tags have a resonance frequencyof more than 10 MHz while for low values the frequency approaches 8.2 MHz.
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| 20. |
- Andersson, Henrik, et al.
(författare)
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Soldering Surface Mount Components onto Inkjet Printed Conductors on Paper Substrate using Industrial Processes
- 2016
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Ingår i: IEEE Transactions on Components, Packaging, and Manufacturing Technology. - 2156-3950 .- 2156-3985. ; 6:3, s. 478-485
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes mounting of standard surface mount component packages on a paper substrate using an industrial solder process with a low-temperature solder. The use of paper as a substrate for printed flexible electronics is becoming more and more widespread as an alternative to the more commonly used plastic substrates, such as polyethylene and polyimide. Paper has the benefits of being environmentally friendly, recyclable, and renewable, as well as inexpensive. It is shown that it is possible to mount standard surface mount device components on paper substrates using low-temperature solder in an industrial soldering process. The contact resistances obtained are mostly low, although the yield of functioning contacts is low. The reason is cracking of the substrate coating layer that goes through the printed silver tracks. It was observed that the cracks appear mostly close to the contact pads, the most likely cause is thermal mismatch between the coating layer and solder and also thermal expansion of the photo paper resin coating. The smallest component package size, 0201, resulted in the highest yield of >80% with decreasing yield for larger package sizes.
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| 21. |
- Andersson, Olov, 1979-, et al.
(författare)
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Real-Time Robotic Search using Structural Spatial Point Processes
- 2020
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Ingår i: 35TH UNCERTAINTY IN ARTIFICIAL INTELLIGENCE CONFERENCE (UAI 2019). - : Association For Uncertainty in Artificial Intelligence (AUAI). ; , s. 995-1005
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Konferensbidrag (refereegranskat)abstract
- Aerial robots hold great potential for aiding Search and Rescue (SAR) efforts over large areas, such as during natural disasters. Traditional approaches typically search an area exhaustively, thereby ignoring that the density of victims varies based on predictable factors, such as the terrain, population density and the type of disaster. We present a probabilistic model to automate SAR planning, with explicit minimization of the expected time to discovery. The proposed model is a spatial point process with three interacting spatial fields for i) the point patterns of persons in the area, ii) the probability of detecting persons and iii) the probability of injury. This structure allows inclusion of informative priors from e.g. geographic or cell phone traffic data, while falling back to latent Gaussian processes when priors are missing or inaccurate. To solve this problem in real-time, we propose a combination of fast approximate inference using Integrated Nested Laplace Approximation (INLA), and a novel Monte Carlo tree search tailored to the problem. Experiments using data simulated from real world Geographic Information System (GIS) maps show that the framework outperforms competing approaches, finding many more injured in the crucial first hours.
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| 22. |
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| 23. |
- 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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| 24. |
- Dancila, Dragos, et al.
(författare)
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Antennas on Paper Using Ink-Jet Printing of Nano-Silver Particles for Wireless Sensor Networks in Train Environment
- 2016
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Ingår i: Microwave and optical technology letters (Print). - : Wiley. - 0895-2477 .- 1098-2760. ; 58:4, s. 754-759
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the design, manufacturing and measurements of antennas on paper, realized using ink-jetprinting of conductive inks based on nano-silver particles (nSPs). The extraction of the substrate characteristicssuch as the dielectric constant and dielectric loss is performed using a printed ring resonator technique. Thecharacterization of the nSPs conductive inks assesses different parameters as sintering time and temperature.Two antennas are realized corresponding to the most common needs for Wireless Sensor Networks (WSN) inTrains Environment. The first one is a patch antenna characterized by a broadside radiation pattern and suitedfor operation on metallic structures. The second one is a quasi-yagi antenna, with an end fire radiation patternand higher directivity, without requiring a metallic ground plane. Both antennas present a good matching (S11 < -20 dB and S11 < -30 dB, respectively) and acceptable efficiency (55 % and 45 %, respectively) for the papersubstrate used at the center frequency of 2.4 GHz, corresponding to the first channel of the IEEE 802.15.4 band.
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| 25. |
- Du, Yijun, et al.
(författare)
-
Design of Sharp Roll-Off Band Notch with Fragment-Type Pattern Etched on UWB Antenna
- 2018
-
Ingår i: IEEE Antennas and Wireless Propagation Letters. - 1536-1225 .- 1548-5757. ; 17:12, s. 2404-2408
-
Tidskriftsartikel (refereegranskat)abstract
- Fragment-type etch patterns are proposed and designed on ultra-wideband planar antenna to acquire sharp roll-off band notch. Multi-objective evolutionary algorithm is applied to achieve the optimization searching of the best fragment-type etch pattern by setting multiple objectives to acquire the exact notched band and challenge the roll-off criterion (ROC) of band notch. Efficiency of the design can be improved by properly presetting slits on the patch radiator. For demonstration, designs with different slit presetting are implemented and tested. With single slit preset, band notch of ROC=0.72 at the WLAN band ranging from 5.15 GHz to 5.85GHz is acquired.
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| 26. |
- Du, Yijun, et al.
(författare)
-
Design of ultra-wideband antenna with high-selectivity band notches using fragment-type etch pattern
- 2020
-
Ingår i: Microwave and optical technology letters (Print). - : Wiley. - 0895-2477 .- 1098-2760. ; 62:2, s. 912-918
-
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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| 27. |
- Forsström, Stefan, 1984-, et al.
(författare)
-
Specialanpassade kurser för yrkesverksamma ingenjörer : Erfarenheter och upplevelser
- 2023
-
Ingår i: Bidrag från den 9:e utvecklingskonferensen för Sveriges ingenjörsutbildningar. - : Mälardalens universitet. - 9789174856200 ; , s. 348-353
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- I dagens samhälle blir det allt viktigare att fortbilda sig under hela sitt yrkesverksamma liv. För att möta efterfrågan på det livslånga lärandet har Mittuniversitetet utvecklat och genomfört ett antal kurser som riktar sig mot yrkesverksamma ingenjörer. Detta arbete presenterar våra erfarenheter av att ge dessa kurser, med en tyngdpunkt på studenternas upplevelser. Syftet med detta är att bygga upp en vetenskaplig bas för vad vi gör som är bra, men även vad som kan förbättras och förändras. Målsättningen är att göra dessa specialanpassade kurser riktade mot yrkesverksamma ingenjörer så givande och flexibla som möjligt. Våra initiala resultat visar bland annat att studenternas negativa upplevelser ofta var kopplade till antagningsförfarandet och det praktiska genomförandet av kurserna. Man hade svårigheter med att hitta hur man skulle registrera sig på kursen och att tidsramen för registrering kunde vara ett problem. Läroplattformen uppfattades som svår att överblicka och det förekom även viss otydlighet gällande var undervisningen skulle äga rum. Den positiva responsen i utvärderingarna gällde främst det faktiska kursinnehållet, då man ansåg att uppgifter och kursmaterial var givande. Vidare uppskattades kursupplägget, att man kunde kombinera studierna med arbete. Framledes kommer vi att fortsätta med dessa utvärderingar i takt med att kurserna ges, och därefter anpassa vårt mottagande och kommunikationen med studenterna. Även kursupplägget ses över kontinuerligt via den återkoppling vi mottar.
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| 28. |
- Gao, Jinlan, et al.
(författare)
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An Analytical Model for Electro-magnetically Coupled UHF RFID Sensor Tags
- 2013
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Ingår i: 2013 IEEE INTERNATIONAL CONFERENCE ON RFID (RFID). - : IEEE conference proceedings. - 9781467357500 - 9781467357487 ; , s. 66-73
-
Konferensbidrag (refereegranskat)abstract
- This paper presents an analytical model for electromagnetically coupled UHF RFID sensor tags where a coupling loop with an embedded sensor is attached to an ordinary UHF RFID tag with a small gap. Electromagnetic coupling is used, in this case, to modulate the properties of the tag antenna in proportion to the values of the embedded sensor. The antenna together with the coupling loop are represented as an equivalent circuit and the analysis of the sensor tag becomes a circuit-level calculation after extracting parameters from full-wave simulations for, respectively, the separated dipole antenna and coupling loop. The results calculated from the equivalent circuit model are compared with the results from full-wave simulations and show good agreement. The presented model can thus be used for analyzing and predicting the behavior of electromagnetically coupled sensor tags. Based on the analysis with the presented model, the methods for optimizing the sensory performance of this kind of RFID sensor tags are also presented in this paper.
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| 29. |
- Gao, Jinlan
(författare)
-
Antenna-based passive UHF RFID sensor tags : Design and application
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- RFID, as a low cost technology with a long life time, provides great potential for transmitting sensor data in combination with the ordinary ID number. The sensor can, for example, be integrated either in the chip or in the antenna of an RFID tag.This thesis focuses on the design of antenna-based UHF RFID sensor tags as wireless sensors at the lowest possible cost level compatible with standard communication systems in logistics. The applications of the sensor tags, in this work, mainly target remote humidity sensing. Antenna-based sensory UHF RFID tags utilize the influence that the physical or chemical parameters to be sensed have on the electrical properties of a tag antenna. The variations of the electrical properties of the tag antenna can be measured in many ways. In the thesis, a description is provided as to how these variations are normally measured by an RFID reader without any other assistant equipment. Three structures of antenna-based RFID sensor tags are presented with detailed characterizations. The first one utilizes the sensitivity of the antenna to the surrounding environment to construct RFID sensor tags, where a moisture absorbing layer providing wetness/humidity sensor functionality is placed on the RFID tag antenna to increase the humidity concentration surrounding the tag antenna and the thesis describes how to overcome certain limitations due to disturbances associated with background materials. The second structure directly integrates a small resistive sensor element into an RFID tag antenna and the sensor information can thus modulate the antenna performance by means of galvanic contact. The third structure embeds a small resistive sensor element into a loop which is positioned on top of the tag antenna and the sensor information can thus modulate the performance of the tag antenna by means of electromagnetic coupling. Both theoretical analysis and fullwave simulations are presented for the latter two sensor tag structures in order to characterize the performance of the sensor tags. An ultra-low cost printed humidity sensor with memory functionality is also designed and thoroughly characterized for integration into RFID tag antennas by means of galvanic contact or electromagnetic coupling. The sensor is a 1-bit write-once-read-many (WORM) memory printed using conductive ink. The WORM works as a pure resistive humidity sensor and can provide information about an historical event. The WORM sensor is presented by introducing its geometry, characterizingits behavior in humidity and explaining the principle of the humidity effect. The WORM sensors are also integrated into the RFID tags by means of both galvanic contact and electromagnetic coupling in order to experimentally verify the two concepts. To lower the cost of the RFID tags, the antennas are normally printed, milledor etched on flexible substrates using low-cost high-speed manufacturing methods which in some cases cause a high degree of edge roughness. The edge roughness will affect the behavior of the antenna, however, the characteristics of edge roughness on RFID antennas have previously not received any significant attention. Unforeseen antenna behavior can affect the antenna-based sensor tags, thus the influence of edge roughness is also investigated in the thesis.
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| 30. |
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| 31. |
- Gao, Jinlan, et al.
(författare)
-
On the Influence of Edge Roughness in High-Speed RFID Antenna Manufacturing Processes
- 2013
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Ingår i: Proceeding of the 34th Progress in Electromagnetics Research Symposium (PIERS 2013). ; , s. 571-576
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Konferensbidrag (refereegranskat)abstract
- High speed manufacturing processes are commonly associated with high mechanical tolerances. For RFID antennas, mechanical manufacturing tolerances imply uncertainties in the antennas outer dimensions as well as in the surface- and line-roughness of the antennas geometry. Rough edges can for example be caused by high speed dry patterning processes. This work investigates the impact that rough patterns along the edges of an antenna structure have on UHF RFID tags' communication capabilities. The work characterizes the negative influence that edge roughness of different levels has on standard RFID dipoles. Results show that, as expected, the performance degradation for an RFID tag antenna increases with increased edge roughness amplitude. The results also show that the performance degradation due to edge roughness is almost identical for the investigated antennas' different line widths when the roughness level is normalized to its specific antenna line width, i.e., an antenna with a wider line width is more robust and can withstand a higher degree of edge roughness.
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| 32. |
- Gao, Jinlan, et al.
(författare)
-
Printed electromagnetic coupler with an embedded moisture sensor for ordinary passive RFID tags
- 2011
-
Ingår i: IEEE Electron Device Letters. - 0741-3106 .- 1558-0563. ; 32:12, s. 1767-1769
-
Tidskriftsartikel (refereegranskat)abstract
- This letter presents a printed UHF RFID sensor solution that indicates if a passive RFID tag has been exposed to a certain degree of moisture. The printed sensor operates as a write-once-read-many (WORM) resistive memory device as it permanently changes its resistance from about 10 to 10 after exposure to moisture or water. A printed coupling loop with an embedded WORM sensor is horizontally placed just above the surface of an ordinary UHF RFID tag. Electromagnetic coupling is used to modulate the properties of the tag antenna by changing its input impedance and introducing ohmic losses in proportion to the embedded sensor values. The passive RFID tag can change state from readable to unreadable when the WORM bit is set, i.e., is put in a low-resistance state. The proposed concept verifies that commercial RFID tags can be used as sensor tags by simply adding an electromagnetically coupled sensor as a sticker or by similar means, without the need for ohmic contacts between the sensor and the original RFID tag. © 2006 IEEE.
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| 33. |
- Gao, Jinlan, et al.
(författare)
-
Printed Humidity Sensor with Memory Functionality for Passive RFID tags
- 2013
-
Ingår i: IEEE Sensors Journal. - 1530-437X .- 1558-1748. ; 13:5, s. 1824-1834
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents a printed UHF RFID sensor solution that indicates whether a passive RFID tag has been exposed to a certain degree of humidity. The printed sensor operates as a Write Once Read Many (WORM) resistive memory as it permanently changes its resistance from about 2 kÙ to less than 50 Ù after exposure to humidity or water. The change of the sensor resistance is used to modulate the properties of a UHF RFID tag antenna by changing antenna input impedance and also introducing or removing ohmic losses in the antenna structure. The final result is reflected in the change of the minimum transmit power required to power-up the RFID tag. Both the sensor and the tag antenna are printed horizontally on a paper substrate. Different geometric combinations of sensor and antenna structures are investigated. Typical applications include non-invasive methods for detecting wetness or humidity levels in hidden locations such as within construction structures. The sensor setup can also serve to provide information as to whether a package sent over a supply chain has exceeded a certain level of humidity during its route.
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| 34. |
- Gao, Jinlan, 1984-, et al.
(författare)
-
Printed Temperature Sensors for Passive RFID Tags
- 2010
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Ingår i: Proceeding of 27th conference in Progress In Electromagnetics Research Symposium (PIERS2010 Xian). ; , s. 835-838
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Konferensbidrag (refereegranskat)
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| 35. |
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| 36. |
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| 37. |
- Jonsson, Peter, et al.
(författare)
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High-Directivity Fractal-Vee Dipoles
- 2002
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Ingår i: IEEE Antennas and Propagation Society, AP-S International Symposium (Digest). - : IEEE conference proceedings. - 0780373308 ; , s. 558-561
-
Konferensbidrag (refereegranskat)
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| 38. |
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| 39. |
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| 40. |
- Li, Xiaotian, et al.
(författare)
-
A Paper-Based Screen Printed HF RFID Reader Antenna System
- 2018
-
Ingår i: IEEE Journal of Radio Frequency Identification. - 445 Hoes Lane Piscataway, NJ 08854, USA : IEEE. - 2469-729X .- 2469-7281. ; 2:3, s. 118-126
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Tidskriftsartikel (refereegranskat)abstract
- Screen printing is a stencil process where conductive inks are patterned onto substrates through a fine mesh of threads. Nowadays, screen printing can be used to print RFID antenna structures onto flexible and ultra-low-cost substrates such as pa-per. In this manuscript, we present an HF RFID reader antenna system, operating at 13.56 MHz, using screen printed Ag particle ink as conductor and using HP photo paper as substrate. The proposed antenna system comprises four loop antenna elements, matched to 50 Ω, and one I2C addressed SP4T multiplexer circuitry, controlled through an exterior embedded system. The geometries, designs and characterizations of the antenna system are described in the manuscript in details. Measurement results show that the antenna system has low power reflections and a suitable Q factor. It has a maximum 11.1 cm RFID tag read range at an antenna system input power of 33 dBm. 2D RFID tag positioning can be enabled by utilizing the RFID tag interrogation zones formed by the four loop antenna elements. In addition, a parametric study is carried out to investigate the effect of loop antenna element DC resistance on the antenna element performance. It can be concluded that the proposed method can be used to create low-cost and large-area HF RFID reader antenna systems.
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| 41. |
- Li, Xiaotian, et al.
(författare)
-
Enabling paper-based flexible circuits with aluminium and copper conductors
- 2019
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Ingår i: IOP Flexible and Printed Electronics. - Temple Way, Bristol BS1 6HG, United Kingdom : IOP Publishing. - 2058-8585. ; 4
-
Tidskriftsartikel (refereegranskat)abstract
- Implementing electronics systems on paper is an important area of flexible circuit technologies. One of the approaches is to print conductive inks onto paper substrates, on which silicon-based surface mount device components are mounted. However, one of the problems is that the printed conductors have unneglectable resistivity. In this paper, we present paper-based flexible circuits, using copper and aluminium conductors that are laminated onto paper substrates using a high-speed roll-to-roll method. Edge roughness inspections and repeated two-point bending tests are carried out to evaluate the manufactured flexible circuits. Three surface mount techniques are used to assemble standard surface mount device components onto the flexible circuits, including an isotropic conductive adhesive, an anisotropic conductive adhesive, and a low-temperature solder paste. Several characterizations are performed to the surface mount techniques, including contact resistance measurements, component bonding strength tests, assembled circuit bending tests, and scanning electron microscopy. The results of the characterizations suggest that flexible circuits made from Cu with paper substrate achieve satisfactory results for mechanical reliability, all surface mount techniques, and have the potential to be used on automatic component assembly lines. In order to test whether such flexible circuits and surface mount techniques can be used in implementing electronics systems, passive NFC tags with relative humidity sensing functionality are made, which are interrogated by an NFC equipped mobile phone.
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| 42. |
- Li, Xiaotian
(författare)
-
Flexible Circuits and Materials for Creating Large-Area RFID Reader Antenna Systems
- 2018
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- One of the applications for RFID technology is to monitor and position RFID-tagged objects over large volumes. To achieve this, one possible option is to implement RFID reader antennas, which are relatively thin but with significantly large areas, and place them beneath the RFID-tagged objects. In order to realise RFID reader antennas with large-areas, circuit materials other than conventional rigid PCB materials should be investigated and utilized. Therefore, this thesis addresses how non-conventional PCB materials can be used to achieve large-area RFID reader antenna structures. Non-conventional PCB materials are firstly chosen, which comprises patterned Al-polyimide foil, printed conductive Ag inks onto paper, polyethylene foam as antenna substrate. The physical and electrical properties of the materials are measured. These properties are later used in antenna simulations. In addition, assembly methods, e.g. circuit lamination and VIA fabrication, for the chosen materials are developed. Three novel surface mounting techniques are developed and characterized in this thesis. The techniques are developed for mounting SMD components onto tracks made by Al, a screen printed Ag flake ink, and an inkjet printed Ag nanoparticle ink. These techniques are characterized and evaluated by various methods, including contact resistance measurements, bonding strength tests, and microscopy studies. The characterizations show these techniques have achieved low contact resistance and sufficient bonding strength. Based on the previous efforts, two antenna systems, respectively operating on UHF (867 MHz) and HF (13.56 MHz) bands, are fabricated. The two antenna systems are designed into SP4T switching networks, using standard antenna elements as the loads of the network. The input RFID interrogation signals from commercial industrial RFID readers are directed into every antenna element periodically through the SP4T switching networks. Both antenna systems are characterized by means of various RF power attenuation measurements and passive RFID tag interrogation tests. It is shown in the results that both antenna systems have low RF attenuations, potentials to perform passive RFID tag positioning, and possibilities to be expanded to larger areas. In the end, based on the antenna system characterization results and design parameters, a great amount of calculation is performed in order to discuss how large the antenna system areas can be as well as how many antenna elements can be achieved in one antenna system.
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| 43. |
- Li, Xiaotian, et al.
(författare)
-
Flexible Circuits and Materials for Large-Area UHF RFID Reader Antenna Systems
- 2018
-
Ingår i: IOP Flexible and Printed Electronics. - : IOP Publishing. - 2058-8585. ; 3:1
-
Tidskriftsartikel (refereegranskat)abstract
- RF electronics commonly incorporate PCB-materials with low loss tangents, which limits its use for large-area applications due to its high cost. This work verifies one alternative solution how non-conventional flexible circuit materials can be used to manufacture large functional surfaces for RF-based applications. Laminated Al foils are used for conducting layers and a flexible foam material is used for substrate. An RFID reader system has been developed to demonstrate the functionality, comprising of eight microstrip antenna elements arranged in a SP4T switching structure covering an area of 1.2 m × 0.6 m. Each antenna element is individually addressable with aid of distributed digital and analogue multiplexer circuitry and it is shown how these components can be soldered directly onto the Al conductors. The constructed system shows good RF performance, both with regards to the materials and to the interconnections with the distributed multiplexer circuitry. It can perform far-field RFID tag reading above its surface without dead zones and the system characterization implies that the concept can be further expanded to cover geometrical areas up to 1000 square meters.
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| 44. |
- Li, Xiaotian, et al.
(författare)
-
Flexible Circuits Based on Aluminum Conductor and Nonwoven Substrate
- 2019
-
Ingår i: 2019 IEEE International Flexible Electronics Technology Conference, IFETC 2019. - : Institute of Electrical and Electronics Engineers Inc.. - 9781728117782
-
Konferensbidrag (refereegranskat)abstract
- Electronic textiles, integrating functional electronics circuits into fabric materials, are emerging as an important branch of flexible circuits. In this paper, we introduce a novel material combination for electronic textiles that can be used in implementing hybrid electronics. This type of circuits is fabricated by laminating patterned aluminum foils onto a nonwoven substrate in a high-speed roll-to-roll method. An isotropic conductive adhesive and an anisotropic conductive adhesive are used to assemble standard surface mount device components onto the fabricated circuits. The surface mount techniques are characterized by means of contact resistance measurements, component bonding strength tests, circuit bending tests, and scanning electron microscopy. An NFC tag with relative humidity sensing functionality is fabricated to evaluate the fabricated circuits to an electronic system level.
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| 45. |
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| 46. |
- Li, Xiaotian, et al.
(författare)
-
Soldering surface mount components on screen printed Ag patterns on paper and Polyimide substrates for hybrid printed electronics
- 2018
-
Ingår i: Flexible and Printed Electronics. - : IOP Publishing. - 2058-8585. ; 3:1
-
Tidskriftsartikel (refereegranskat)abstract
- The development of printed electronics on flexible substrates is increasing rapidly, where the main benefit is large area and low cost. However, the functionality and performance of printed circuits cannot compete with standard silicon based microprocessors or integrated circuits, though the functionality and performance of printed circuits are increasing. Therefore, in this work we investigate the possibilities of using Sn42/Bi57.6/Ag0.4 low-temperature solder paste together with a reflow solder oven and hot air solder iron to mount regular SMD components on screen-printed silver tracks. It was found that it is possible to solder standard Si SMD pack-ages onto screen-printed Ag ink tracks on paper substrate, however, the component bonding strength to Polyimide were not satisfactory. The resistance of the solder joints was found to be no more than 240 mΩ. The bond strength was found to be higher using the manual hot air sol-der iron than the reflow solder oven. Bending tests show that the bonding strength is higher for the hot air soldered components. Reference samples on FR-4 based copper PCB show a bond strength ~10 times higher but we conclude that it is possible to solder regular Si SMD components onto Ag-printed conductors on paper substrate with good results. The process could be used to fabricate hybrid printed electronics on a standard solder process line.
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| 47. |
- Li, Xiaotian
(författare)
-
Towards Large-Area Electronic Systems Using Non-Conventional Substrate and Conductor Materials
- 2020
-
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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| 48. |
- Li, Xiaotian, et al.
(författare)
-
UHF RFID Shelf Reader Antennas for Object Classification and Distance Estimation of Non-Tagged RFID Objects
- 2017
-
Ingår i: 2017 Ieee International Conference On Microwaves, Antennas, Communications And Electronic Systems (Comcas). - : IEEE. - 9781538631690 ; , s. 289-292
-
Konferensbidrag (refereegranskat)abstract
- RFID readers serve the obvious role of extracting information from RFID tagged objects. Objects without RFID tags or objects with tags that for some reason are unreadable will not be noted at all when positioned within an RFID reader antenna's interrogation zone. In this paper, we investigate how UHF RFID reader systems for smart shelf applications could also be used for classification and distance estimation of non RFID tagged objects, if the reader modules provide access to antenna S-parameters. The investigation is performed with an inset fed microstrip antenna where objects of different materials are positioned at different heights above the antenna. It is shown how objects are detected and classified in terms of their materialistic properties through S-parameter analysis and how the distance from the antenna to the object could be estimated.
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| 49. |
- Neubauer, Björn, et al.
(författare)
-
A new thermally activated battery cell-based forest fire detection and monitoring system
- 2012
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Ingår i: WIT Transactions on Ecology and the Environment. - Southampton : WIT Press. - 9781845645847 ; , s. 113-124
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Detection of forest wildfires at early stages can significantly improve the success of fire fighting and thus it contributes to the damage and cost reduction. Surface deployed sensor networks linked to global nets are often regarded as technically simple options to achieve forest fire detection and progress monitoring. Straightforward solutions with sensor nodes continuously supplying telemetric information demand heavy duty power supplies and periodic service. They are relatively expensive and commonly not environmentally friendly. We have suggested and currently develop an early warning forest fire detection system based on inexpensive, dormant fire-activated detecting sensors and a number of monitoring nodes in a network configuration. Small deploy-and-forget type sensors contain a radio transmitter with recorded identity number, together with an inactive power element. When activated by high temperature of a developing wildfire, this element produces enough power to support the transmitter, broadcasting the unique identity code until the sensor is completely burnt. Monitoring nodes of such system stand by for sensor activation and forward the alarm information along the monitoring nodes network. Implementation of anti-collision transmission protocols in the sensors allows the monitoring nodes to keep track of fire development and progress. Monitoring nodes and nodes linking the forest fire detection and monitoring net to public networks can be made using conventional technology and utilizing existing communication networks. Thus significant efforts have been directed to the design of the primary sensors, designing them to be cost efficient and minimizing their environmental impact. Cellulose-based materials are widely used in the sensor construction to decrease its environmental impact and cost. The core of the sensor power element is made of laminated and screen-printed cellulose- based substrates. The power element is activated by a small amount of water, trapped in crystal hydrate salts in storage and released by elevated temperatures of the fire. These salt-based sensors can be manufactured in a rollto- roll manner, making them cost effective. Absence of any liquids or gels in the sensor construction will guarantee a good shelf time. © 2012 WIT Press.
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| 50. |
- Nilsson, Hans-Erik, et al.
(författare)
-
An incontinence alarm solution utilizing RFID based sensor technology
- 2011
-
Ingår i: 2011 IEEE International Conference on RFID-Technologies and Applications, RFID-TA 2011. - Sitges : IEEE conference proceedings. - 9781457700279 ; , s. 359-363
-
Konferensbidrag (refereegranskat)abstract
- The current work addresses the challenge of measuring urine volume in diapers primarily targeting geriatric care applications. There are number of incontinence alarm innovations suggested and described in patents and scientific reports. However, there are hardly any reports of such systems in permanent use in the hospital care market. One reason might be the challenging system requirements of such applications. According to our own experiences and requirements reported in the literature those are truly demanding. We need meter long communication range, passive sensor functionality, robust and safe measurement, unobtrusive sensor device design (patient) and a convenient reader and user interface (care personal). The list of specifications can be added to, a very low price adding only a small fraction to the over all diaper cost. Finally the system should improve the comfort of the patient and increase diaper management efficiency, reducing the costs of the care provider. The recent progress and usage of RFID technology have reduced the cost levels for inlays and readers. Thus, standard RFID inlays may be a candidate providing the targeted functionality in a smart diaper. In this work we evaluate the possibility to use the RFID antenna as the sensor element when detecting when a diaper has reached a certain degree of urine saturation. The evaluation has been done in a laboratory setup, with real test persons providing authentic readout scenarios. © 2011 IEEE.
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