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  • 101.
    Ashraf, Shakeel
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Thermal detector with integrated absorber structure for mid-IR gas detection2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Measurement of the concentration of greenhouse gases, such as carbon dioxide(CO 2 ) and methane (CH 4 ), in the atmosphere has received significant attention in the last few decades. This work focusses on the development of high-performance thermopile detectors for use with the non-dispersive infrared (NDIR) measurements of such gases. The performance of the thermopile detectors could effectively be increased by selecting membrane materials with a low thermal conductivity value and an efficient infrared (IR) absorbing material and by selecting the materials with high Seebeck coefficient values. Graphite black paint can be used as a radiation absorber, as it has high absorption (80—93%) for a wide spectral range (2.5 μm — 20 μm). By using spray paint or a paint brush, the application of the absorber is simple and fast. However, the control over the processing process suffers with these simple methods. The thermal capacitance of the detector will rapidly increase due to uneven distribution and unknown thickness of the absorber, although the response of the thermopile detector will be maximum due to high absorption; however, the response time (τ th )for the detector will be longer.In order to improve the performance, IR absorbers have been designed to utilise the membrane (SU-8 epoxy) of the detector as an active part of the IR absorber. This utilisation of the SU-8 epoxy membrane will result in a maximum detector sensitivity and a minimum increase in both the thermal capacitance and thermal conductance of the thermopile detector. Absorber structures, based on SU-8 epoxy, with a narrow absorption band at 4.26 µm and a wider multi-layered absorption band at 3-6 µm, were designed, simulated, and fabricated, and their integration into the membrane of thermopile detectors have been presented. The response of the thermopile detector could also be increased by using materials with high Seebeck coefficient [1] values such as semiconductor materials, as they have higher Seebeckvalues compared to the metals. In the thesis, molybdenum disulfide (MoS 2 ) flakes were characterised, and Seebeck values were estimated through a measurement setup as a function of temperature difference (ΔT). The fabricated thermopile detectors were characterised, and the response time(τ th ) of a thermocouple with a multi-layered absorber structure has been estimated to be 21 ms. The detector has shown high responsivity value in the wavelength range of 3 µm – 4.5 µm, which is used for CO 2 and CH 4 detection. The thermopile detector was evaluated for CO 2 gas through a long-path-length NDIR platform. The results show that the evaluated thermopile could be used for the measurement of gas concentration down to levels of a few parts per million (ppm) by using the long-path-length NDIR platform.

  • 102.
    Ashraf, Shakeel
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Mattsson, Claes
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Thungström, Göran
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Fabrication and characterization of a SU8-epoxy membrane based thermopile detector with an integrated multilayered absorber structure for the mid-IR region2019In: IEEE Sensors Journal, ISSN 1530-437X, E-ISSN 1558-1748, Vol. 19, no 11, p. 4000-4007Article in journal (Refereed)
    Abstract [en]

    This paper reports on the fabrication and characterization of a thermopile detector with an integrated mid-infrared absorber structure. The fabricated absorber structure has shown an absorption of more than 95% in the wavelength range of 3.2 – 5.47 μm. The detector was fabricated with standard cleanroom process techniques and equipment. The serial resistance was measured at about 315 kΩ at room temperature. The photosensitivity of the detector was characterized for a signle wavelength (4.26 µm) and a band of wavelength ranging from 2.5 –5.5 µm through two different measurement setups. In the first measurement setup, the photosensitivity was estimated at 57.5 V·mm2·W-1 through a MEMS-based infrared radiation source and with an optical band-pass filter of wavelength 4.26µm. The following characterization was performed to characterise the photosensitivity of the detector in a broader wavelength range. This measurement was taken using a monochromator setup utilizing a reference photodetector for calculations of the optical power of the infrared source. The photosensitivity and the specific detectivity (D*) of the fabricated detector were measured to values of 30-92 V·W-1 and 8.0×107-2.4×108 cm·Hz1/2·W-1, respectively, in the wavelength range of 2.8 – 5 µm. The time constant was estimated to around 21 ms

  • 103.
    Ashraf, Shakeel
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Mattsson, Claes
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Thungström, Göran
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Fabrication of a mid-Ir sensitive thermopile detector2016In: Proceedings of IEEE Sensors, IEEE, 2016, article id 7808481Conference paper (Refereed)
    Abstract [en]

    This paper reports on the integration of a multilayered mid-infrared absorber structure into a SU-8 epoxy membrane-based thermopile detector. The absorber structure was designed and simulated using transfer matrix theory. The fabricated absorber structures were characterized through Fourier transform infrared spectroscopy. The structure shows an absorption of more than 95% in the wavelength range of 3.30pm–5pm for simulations, and 3.2pm–5.47pm for FTIR measurements. The complete fabrication process of a thermopile detector including the integration of a multilayered absorber structure has been presented. A MEMS based infrared emitter was used to characterize the fabricated detector. The serial resistance was measured to 315 kΩ and the responsivity was calculated to 57.5 Vmm2W−1 at a wavelength of 4.26pm. The time constant for the fabricated detector was estimated to around 21ms.

  • 104.
    Ashraf, Shakeel
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Mattsson, Claes
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Thungström, Göran
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Gaynullin, B.
    Research and Development Department, SenseAir AB, Delsbo.
    Rödjegård, H.
    Research and Development Department, SenseAir AB, Delsbo.
    Evaluation of a CO2 sensitive thermopile with an integrated multilayered infrared absorber by using a long path length NDIR platform2018In: I2MTC 2018 - 2018 IEEE International Instrumentation and Measurement Technology Conference: Discovering New Horizons in Instrumentation and Measurement, Proceedings, IEEE, 2018, p. 1-6Conference paper (Refereed)
    Abstract [en]

    In this work, a mid-infrared-sensitive thermopile detector was evaluated for carbon dioxide gas. The thermopile has an integrated absorber structure that has more than 95% absorption for the wavelength range of 3.3-5.5 μm. For the measurement of carbon dioxide, the detector was initially assembled on a small printed circuit board holder and then installed in a long path length non-dispersive infrared platform. The measurement setup was calibrated by exposing the detector to carbon dioxide of known concentrations (from 50 ppm to 1,300 ppm) and measuring the corresponding voltage response of the detector. The measured voltage values allowed us to calculate the calibration constant for this detector. This was followed by a verification process using a concentration of 500 ppm (which was not used in the calibration) and a known value of 1,300 ppm. The verification results matched with real values, demonstrating that the sensor can be used for highly sensitive and accurate carbon dioxide measurements at concentrations from a few ppm level up to 1,300 ppm. Above this level, additional calibration is needed. 

  • 105.
    Ashraf, Shakeel
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Mattsson, Claes
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Thungström, Göran
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Rödjegard, Henrik
    Design of a multilayered absorber structure based on SU-8 epoxy for broad and efficient absorption inMid-IR sensitive thermal detectors2014In: Proceedings, 2014, p. 938-941Conference paper (Refereed)
    Abstract [en]

    This paper reports on design, simulation and fabrication of a multilayered interferometric absorption structure with a broad absorption in the mid-infrared band. This region is used for IR based CH4 and CO2 detection. The structure consists of five layers of different thickness. The structure consists of one mirror layer of aluminium, two SU-8 epoxy layers and two thin titanium layers. This structure has been fabricated on a silicon substrate and verified for its absorption properties through Fourier transform infrared spectroscopy. The fabricated structure has been compared with simulations are performed using transfer matrix theory. The structure shows more than 90% absorption in the wavelength range of 3.20μm - 5.35μm for simulations and 3.13μm - 5.47μm for FT-IR measurements. The transmission and reflection of SU-8 epoxy was measured using FT-IR (that), resulting in a calculated absorption between 10 - 20% in the area of interest (3μm - 6μm). The use of SU-8 epoxy as dielectric medium, allows for direct integration of the structure into the membrane of a SU-8 membrane based thermopile. The integration results in minimum increase of the thermal capacitance and conductance, which results in maximum detector sensitivity and minimum time constant.

  • 106.
    Ashraf, Shakeel
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Mattsson, Claes
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Thungström, Göran
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Rödjegard, Henrik
    SenseAir AB, Delsbo, Sweden.
    Integration of an interferometric IR absorber into an epoxy membrane based CO2 detector2014In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 9, no 5, p. Art. no. C05035-Article in journal (Refereed)
    Abstract [en]

    Measurements of carbon dioxide levels in the environment are commonly performedby using non-dispersive infrared technology (NDIR). Thermopile detectors are often used in NDIRsystems because of their non-cooling advantages. The infrared absorber has a major influence onthe detector responsivity. In this paper, the fabrication of a SU-8 epoxy membrane based Al/Bithermopile detector and the integration of an interferometric infrared absorber structure of wavelength around 4 µ m into the detector is reported. The membrane of thermopile detector has beenutilized as a dielectric medium in an interferometric absorption structure. By doing so, a reduction in both thermal conductance and capacitance is achieved. In the fabrication of the thermopile,metal evaporation and lift off process had been used for the deposition of serially interconnectedAl/Bi thermocouples. Serial resistance of fabricated thermopile was measured as 220 kΩ. Theresponse of fabricated thermopile detector was measured using a visible to infrared source of radiation flux 3.23 mW mm−2. The radiation incident on the detector was limited using a band passfilter of wavelength 4.26 µ m in front of the detector. A responsivity of 27.86 V mm2W−1at roomtemperature was achieved using this setup. The fabricated detector was compared to a referencedetector with a broad band absorber. From the comparison it was concluded that the integratedinterferometric absorber is functioning correctly.

  • 107.
    Aslam, Muhammad Shehryar
    et al.
    National University of Sciences and Technology (NUST), Pakistan.
    Khan, Alishba
    National University of Sciences and Technology (NUST), Pakistan.
    Atif, Abeera
    National University of Sciences and Technology (NUST), Pakistan.
    Hassan, Syed Ali
    National University of Sciences and Technology (NUST), Pakistan.
    Mahmood, Aamir
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Qureshi, Hassaan Khaliq
    National University of Sciences and Technology (NUST), Pakistan.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Exploring Multi-Hop LoRa for Green Smart Cities2019In: IEEE Network, ISSN 0890-8044, E-ISSN 1558-156XArticle in journal (Refereed)
    Abstract [en]

    With the growing popularity of Internet-of-Things (IoT)-based smart city applications, various long-range and low-power wireless connectivity solutions are under rigorous research. LoRa is one such solution that works in the sub-GHz unlicensed spectrum and promises to provide long-range communication with minimal energy consumption. However, the conventional LoRa networks are single-hop, with the end devices connected to a central gateway through a direct link, which may be subject to large path loss and hence render low connectivity and coverage. This article motivates the use of multi-hop LoRa topologies to enable energy-efficient connectivity in smart city applications. We present a case study that experimentally evaluates and compares single-hop and multi-hop LoRa topologies in terms of range extension and energy efficiency by evaluating packet reception ratio (PRR) for various source to destination distances, spreading factors (SFs), and transmission powers. The results highlight that a multi-hop LoRa network configuration can save significant energy and enhance coverage. For instance, it is shown that to achieve a 90% PRR, a two-hop network provides 50% energy savings as compared to a single-hop network while increasing 35% coverage at a particular SF. In the end, we discuss open challenges in multi-hop LoRa deployment and optimization.

  • 108.
    Assoufid, Lahsen
    et al.
    Advanced Photon Source, Argonne National Laboratory, USA.
    Graafsma, Heinz
    Photon-Science Detector Group, Deutsches Elektronen-Synchrotron, Germany.
    Next-generation materials for future synchrotron and free-electron laser sources2017In: MRS bulletin, ISSN 0883-7694, E-ISSN 1938-1425, Vol. 42, no 6, p. 418-423Article in journal (Refereed)
    Abstract [en]

    The development of new materials and improvements of existing ones are at the root of the spectacular recent developments of new technologies for synchrotron storage rings and free-electron laser sources. This holds true for all relevant application areas, from electron guns to undulators, x-ray optics, and detectors. As demand grows for more powerful and efficient light sources, efficient optics, and high-speed detectors, an overview of ongoing materials research for these applications is timely. In this article, we focus on the most exciting and demanding areas of materials research and development for synchrotron radiation optics and detectors. Materials issues of components for synchrotron and free-electron laser accelerators are briefly discussed. The articles in this issue expand on these topics.

  • 109.
    Atif, Sohaib
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems. Mid sweden University.
    Cooperative diversity and downlink power control using PARPS with application to LTE services (eMBMS and CoMP)2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Mobile devices and their applications are continuing to develop and the more advanced they are, the more they require high data ranges and the more they demand of the available wireless communication networks. At present, LTE (Long Term Evolution) is a good solution as it provides the users of mobile devices with a good throughput and a low latency. In the future, the two most important aspects for end users will be system spectral efficiency and system power controlling. This thesis deals with LTE downlink spectral efficiency and power controlling. The thesis will show how, by using IP multicasting for the LTE downlink, the base station is able to provide the necessary data through a significantly smaller spectrum and, additionally, how cooperative diversity, i.e. the cooperation between several base stations, can improve or even maximise the total network channel capacity, regardless of bandwidth size. A Packet and Resource Plan Scheduling algorithm (PARPS) is used to schedule the transmissions, and the results are calculated in MATLAB. By this means it is possible to analyse the efficiency of the spectrum management, the coverage probability and the power controlling for the different transmitters used for the LTE downlink.The LTE downlink scheme is simulated in Matlab for different numbers of transmitters (2-3). IP multicasting over the LTE downlink manages to transmit the same amount of data using less transmission power (50- 66.6%) with a better system spectral efficiency.

  • 110. Aubry-Fortuna, V.
    et al.
    Perrossier, J.L.
    Mamor, M.
    Meyer, F.
    Fröjdh, Christer
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Thungström, Göran
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Bodnar, S.
    Regolini, J.L.
    What is the role of the metal on the Fermi-level position at the interface with IV-IV compounds?1997In: Microelectronic Engineering, ISSN 0167-9317, Vol. 37/38, no 1, p. 573-579Article in journal (Refereed)
  • 111. Aunet, S.
    et al.
    Oelmann, Bengt
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Abdalla, Suliman
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Berg, Y.
    Reconfigurable Subthreshold CMOS Perceptron2004In: IEEE International Joint Conference on Neural Networks 2004, 2004Conference paper (Refereed)
  • 112. Aunet, Snorre
    et al.
    Oelmann, Bengt
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    200 mV Full Adder Based on a Reconfigurable CMOS Perceptron2004In: Proceedings of IEEE International Conference on Signals and Electronic Systems, 2004Conference paper (Refereed)
  • 113. Aunet, Snorre
    et al.
    Oelmann, Bengt
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Lande, Tor-Sverre
    Yngvar, Berg
    Multifunction Subthreshold Gate used for a Low Power Full Adder2004In: Proceedings of the IEEE Norchip Conference, 2004Conference paper (Refereed)
  • 114. Aunet, Snorre
    et al.
    Oelmann, Bengt
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Norseng, Per Andreas
    Berg, Yngvar
    Real-time reconfigurable subthreshold CMOS perceptron2008In: IEEE Transactions on Neural Networks, ISSN 1045-9227, E-ISSN 1941-0093, Vol. 19, no 4, p. 645-657Article in journal (Refereed)
    Abstract [en]

    In this paper, a new, real-time reconfigurable perceptron circuit element is presented. A six-transistor version used as a threshold gate, having a fan-in of three, producing adequate outputs for threshold of T = 1, 2 and 3 is demonstrated by chip measurements. Subthreshold operation for supply voltages in the range of 100-350 mV is shown. The circuit performs competitively with a standard static complimentary metal-oxide-semiconductor (CMOS) implementation when maximum speed and energy delay product are taken into account, when used in a ring oscillator. Functionality per transistor is, to our knowledge, the highest reported for a variety of comparable circuits not based on floating gate techniques. Statistical simulations predict probabilities for making working circuits under mismatch and process variations. The simulations, in 120-nm CMOS, also support discussions regarding lower limits to supply voltage and redundancy. A brief discussion on bow the circuit may be exploited as a basic building block for future defect tolerant mixed signal circuits, as well as neural networks, exploiting redundancy, is included.

     

  • 115.
    Aurangzeb, Khursheed
    et al.
    King Saud Univ, Riyadh, Saudi Arabia; COMSATS Inst Informat Technol, Attack, Pakistan.
    Alhussein, Musaed
    King Saud Univ, Riyadh, Saudi Arabia.
    O'Nils, Mattias
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Analysis of Binary Image Coding Methods for Outdoor Applications of Wireless Vision sensor Networks2018In: IEEE Access, E-ISSN 2169-3536, Vol. 6, p. 16932-16941Article in journal (Refereed)
    Abstract [en]

    The processing of images at the vision sensor nodes (VSN) requires a high computation power and their transmission requires a large communication bandwidth. The energy budget is limited in outdoor applications of wireless vision sensor networks (WVSN). This means that both the processing of images at the VSN and the communication to server must be energy efficient. The wireless communication of uncompressed data consumes huge amounts of energy. Data compression methods are efficient in reducing data in images and can be used for the reduction in transmission energy. We have evaluated seven binary image coding techniques. Our evaluation is based on the processing complexity and energy consumption of the compression methods on the embedded platforms. The focus is to come up with a binary image coding method, which has good compression efficiency and short processing time. An image coding method with such attributes will result in reduced total energy requirement of the node. We have used both statistically generated images and real captured images, in our experiments. Based on our results, we conclude that International Telegraph and Telephone Consultative Committee Group 4, gzip_pack and JPEG-LS are suitable coding methods for the outdoor applications of WVSNs.

  • 116.
    Aurangzeb, Khursheed
    et al.
    Computer Engineering Department, College of Computer and Information Sciences, King Saud University, Riyadh 11543, Saudi Arabia.
    Alhussein, Musaed
    Computer Engineering Department, College of Computer and Information Sciences, King Saud University, Riyadh 11543, Saudi Arabia.
    O'Nils, Mattias
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Data Reduction Using Change Coding for Remote Applications of wireless Visual Sensor Networks2018In: IEEE Access, E-ISSN 2169-3536, Vol. 6, p. 37738-37747Article in journal (Refereed)
    Abstract [en]

    The data reduction capability of image compression schemes is limited by the underlying compression technique. For applications with minor changes between consecutive frames, change coding can be used to further reduce the data. We explored the efficiency of change coding for data reduction in a wireless visual sensor network (WVSN). This paper presents an analysis of the compression efficiency of change coding for a variety of changes, such as different shapes, sizes, and locations of white objects in adjacent sets of frames. Compressing change frame provides a better performance compared with compressing the original frames for up to 95% changes in the number of objects in adjacent frames. Due to illumination noise, the size of the objects increases at its boundaries, which negatively affects the performance of change coding. We experimentally proved that the negative impact of illumination noise could be reduced by applying morphology on the change frame. Communication energy consumption of the VSN is dependent on the data that are transmitted to the server. Our results show that the communication energy consumption of the VSN can be reduced by 27%, 29%, and 46% by applying change coding in combination with JBIG2, Group4, and Gzip_pack, respectively. The findings presented in this paper will aid researchers in enhancing the compression potential of image coding schemes in the energy-constrained applications of WVSNs.

  • 117.
    Aydogan, Emre
    et al.
    Hacettepe University, Ankara, Turkey.
    Yilmaz, Selim
    Hacettepe University, Ankara, Turkey.
    Sen, Sevil
    Hacettepe University, Ankara, Turkey.
    Butun, Ismail
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Forsström, Stefan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    A Central Intrusion Detection System for RPL-Based Industrial Internet of Things2019In: 2019 15th IEEE International Workshop on Factory Communication Systems (WFCS), IEEE, 2019, article id 8758024Conference paper (Refereed)
    Abstract [en]

    Although Internet-of-Things (IoT) is revolutionizing the IT sector, it is not mature yet as several technologies are  still being offered to be candidates for supporting the backbone of this system. IPv6 Routing Protocol for Low-Power and Lossy Networks (RPL) is one of those promising candidate technologies to be adopted by IoT and Industrial IoT (IIoT). Attacks against RPL have shown to be possible, as the attackers utilize the unauthorized parent selection system of the RLP protocol. In this work, we are proposing a methodology and architecture to detect intrusions against IIoT. Especially, we are targeting to detect attacks against RPL by using genetic programming. Our results indicate that the developed framework can successfully (with high accuracy, along with high true positive and low false positive rates) detect routing attacks in RPL-based Industrial IoT networks.

  • 118.
    Backlund, Hans-Olof
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Höglund, Hans
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Gradin, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Study of tangential forces and temperature profiles in commercial refiners2003In: 2003 International Mechanical Pulping Conference, 2003, p. 379-388Conference paper (Refereed)
  • 119.
    Badel, X
    et al.
    KTH.
    Galeckas, A
    Linnros, Jan
    KTH.
    Kleimann, Pascal
    KTH.
    Fröjdh, Christer
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Petersson, Sture
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Improvement of an X-ray imaging detector based on a scintillating guides screen2002In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 487, no 1-2, p. 129-135Article in journal (Refereed)
  • 120. Badel, X.
    et al.
    Linnros, J.
    Kleimann, P.
    Norlin, Börje
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Koskiahde, E.
    Valpas, K.
    Nenonen, S.
    Petersson, Sture
    Department of Microelectronics, Roy. Inst. of Technology of Sweden, Kista.
    Fröjdh, Christer
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Metallized and Oxidized Silicon Macropore Arrays Filled with a Scintillator for CCD-based X-ray Imaging Detectors2004In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 51, no 3 Part 3, p. 1001-1005Article in journal (Refereed)
    Abstract [en]

    Silicon Charge Coupled Devices (CCD)covered with a scintillating film are now available on the market for use in digital medical imaging. However, these devices could still be improved in terms of sensitivity and especially spatial resolution by coating the CCD with an array of scintillating waveguides. In this work, we fabricated such waveguides by first etching pores in silicon, then performing metallization or oxidation of the pore walls and finally filling the pores with CsI(Tl). The resulting structures were observed using SEM and tested under X-ray exposure. The detector performances were also compared with simulations, indicating that the optimal pore depth for metallized macropore arrays is about 80 um while it is around 350 um for oxidized ones. This result, together with the roughness of the metal coating, explains why lower performances were measured experimentally with the metallized macropores. Indeed, our macropore arrays had depths in the range of 210-390 um, which is favorable to oxidized structures.

  • 121.
    Badel, X
    et al.
    KTH.
    Norlin, Börje
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Kleimann, P
    Université Claude Bernard Lyon-I, France.
    Williams, L
    Applied Scintillation Technology, United Kingdom.
    Moody, S.J.
    Applied Scintillation Technology, United Kingdom.
    Tyrrell, G.C.
    Applied Scintillation Technology, United Kingdom.
    Fröjdh, Christer
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Linnros, J
    KTH.
    Performance of Scintillating Waveguides for CCD-based X-ray Detectors2006In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 53, no 1, p. 3-8Article in journal (Refereed)
    Abstract [en]

    Scintillating films are usually used to improve the sensitivity of CCD-based X-ray imaging detectors. For an optimal spatial resolution and detection efficiency, a tradeoff has to be made on the film thickness. However, these scintillating layers can also be structured to provide a pixellated screen. In this paper, the study of CsI(Tl)-filled pore arrays is reported. The pores are first etched in silicon, then oxidized and finally filled with CsI(Tl) to form scintillating waveguides. The dependence of the detector sensitivity on pore depth, varied from 40 to 400 µm here, follows rather well theoretical predictions. Most of the detectors produced in this work have a detective quantum efficiency of the incoming X-ray photons of about 25%; however, one detector shows that higher efficiency can be achieved. The comparison of its efficiency to a 1-mm thick CsI(Tl) crystal indicates that light collection efficiency in the guides may approach what is theoretically possible. Imaging capabilities of the detectors are demonstrated.

  • 122.
    Bader, Sebastian
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Enabling autonomous envionmental measurement systems with low-power wireless sensor networks2011Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Wireless Sensor Networks appear as a technology, which provides the basisfor a broad field of applications, drawing interest in various areas. On theone hand, they appear to allow the next step in computer networks, buildinglarge collections of simple objects, exchanging information with respect totheir environment or their own state. On the other hand, their ability tosense and communicate without a fixed physical infrastructure makes theman attractive technology to be used for measurement systems.Although the interest inWireless Sensor Network research is increasing,and new concepts and applications are being demonstrated, several fundamentalissues remain unsolved. While many of these issues do not requireto be solved for proof-of-concept designs, they are important issues to beaddressed when referring to the long-term operation of these systems. Oneof these issues is the system’s lifetime, which relates to the lifetime of thenodes, upon which the system is composed.This thesis focuses on node lifetime extension based on energy management.While some constraints and results might hold true from a moregeneral perspective, the main application target involves environmental measurementsystems based onWireless Sensor Networks. Lifetime extensionpossibilities, which are the result of application characteristics, by (i) reducingenergy consumption and (ii) utilizing energy harvesting are to be presented.For energy consumption, we show howprecise task scheduling due to nodesynchronization, combined with methods such as duty cycling and powerdomains, can optimize the overall energy use. With reference to the energysupply, the focus lies on solar-based solutions with special attentionplaced on their feasibility at locations with limited solar radiation. Furtherdimensioning of these systems is addressed.It will be shown, that for the presented application scenarios, near-perpetualnode lifetime can be obtained. This is achieved by focusing on efficient resourceusage and by means of a carefully designed energy supply.

  • 123.
    Bader, Sebastian
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    On the lifetime and usability of environmental monitoring wireless sensor networks2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Wireless sensor networks have been demonstrated, at an early stage in their development, to be a useful measurement technology for environmental monitoring applications. Based on their independence from existing infrastructures, wireless sensor networks can be deployed in virtually any location and provide sensor samples in a spatial and temporal resolution, which otherwise would only be achievable at high cost or involve significant work by humans.The feasibility of the usage of wireless sensor networks in real-world applications, however, is only maintained if certain technological challenges are overcome. Amongst these challenges, are the limited lifetime of the distributed sensor nodes, and user interfaces, which allow for the technology to be utilized in an efficient manner. Contributions to the solution of these challenges have been the objective of this thesis.

    After an analysis of the contributions wireless sensor networks can provide

    to the application domain of environmental monitoring, and the introduction

    to the restrictions, which are posed by a limited operational lifetime and low

    system usability, these issues are addressed at the system level of sensor nodedevices.

    The lifetime of sensor nodes, which is closely linked to the lifetime of the

    complete wireless sensor network, is addressed with regards to the energy

    efficiency of nodes, as well as the utilization of solar energy harvesting in

    order to increase the available energy resources. With respect to energy

    efficiency, an analysis has been performed of the contributions to the energy

    consumption of environmental monitoring sensor nodes, which leads to the

    desire to minimize the nodes' duty cycles and quiescent currents. A sensor

    node design is presented, which features energy efficiency as a key attribute by utilizingmodern semiconductor architectures. Moreover, an argument for the usage of synchronization-based, contention-free communication is made

    in order to reduce active communication periods and, thus, the duty cycle

    of a sensor node. A synchronization method with its focus on low protocol

    overhead is introduced as a basis for such communication forms. After an initial feasibility study in relation to using battery-less solar energy

    harvesting architectures in locations with limited solar irradiation, multiple

    architectural implementations are analyzed in a comparative manner.

    Among these comparisons is an analysis of short-termenergy storage devices in the form of double-layer capacitors and thin-film batteries, which provide prolonged component lifetimes than those for conventional secondary batteries, but which can only buffer for short periods of time due to their limited energy capacity. In order to be able to dimension such energy harvesting systems with respect to the individual application constraints at hand, state of charge simulations are proposed. Amethod for such simulations is presented and demonstrated for the implementation of an energy harvester model on a component basis. While the modeling in this manner is time consuming, the model can predict the state of charge of the energy buffer in the architecture with a high level of accuracy. Finally, a method for the systematic evaluation of solar energy harvesting architectures is presented. The presented method can be summarized as a solar energy harvesting testbed, which utilizes configurable energy harvesting circuits in order to create a deploy-once-test-many type of system. The output results of this testbed can significantly improve

    the efficiency of architecture comparisons and system modeling.

    Contributions to the improvement of the usability of wireless sensor nodes

    are made on two separate levels, namely, developer usability and end user

    usability. A method for the programming of sensor nodes based on hierarchical finite state machines is presented, which improves the usability of software development by creating familiarity for technically experienced

    users. Moreover, the utilization of finite state machine principles allows

    for the software to be developed in a systematic andmodular manner. As

    implemented applications typically require to be verified, which, in the environmental monitoring domain, usually results in outdoor deployments,

    usability considerations for sensor nodes are presented, which can simplify

    this process. Special attention has been paid in order for these improvements to be achieved with low overheads. While software development is a familiar concept for most system developers, this is not the case for the end users of these systems, who are typically domain experts. In order to allow for wireless sensor nodes to be operated

    by domain experts, a method for the configuration of sensor nodes has been proposed.The method uses a combination of graphical specification of the node behavior and a configurable sensor node. Theevaluation of this method, which has been based on a proof-of-concept implementation, demonstrated that the performance can remain high, while end users, without technical experience, are enabled to configure sensor nodes without prior training.

    In summary, the contributions, presented in this thesis, address system

    lifetime and usability with regards to the sensor node level. The results have

    led to the implementation of an energy efficient sensor node, which allows for the operation frombattery-less solar energy harvesting sources. Furthermore, support tools for the implementation of these nodes, both on the hardware and software level, have been proposed.

  • 124.
    Bader, Sebastian
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Anneken, Mathias
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Goldbeck, Manuel
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Oelmann, Bengt
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    SAQnet: Experiences from the Design of an Air Pollution Monitoring System Based on Off-the-Shelf Equipment2011In: Proceedings of the 2011 7th International Conference on Intelligent Sensors, Sensor Networks and Information Processing, ISSNIP 2011, IEEE conference proceedings, 2011, p. 223-228Conference paper (Refereed)
    Abstract [en]

    Nowadays, air pollution is monitored with accurate, but large-sized measurement stations, leading to an overall limited number of monitored locations. Combining these stations, with a higher number of less accurate stations can provide additional information, such as with regards to pollutant distributions. In this paper we present the design, implementation and initial results of such stations based on Wireless Sensor Network technology. For the implementation of the network purely off-the-shelf equipment was chosen, which allows us to analyze the current status of commercially available Wireless Sensor Network technology. While the system was fully implemented and demonstrated operationally, the experiences found during the project showed a limited matureness with regards to the off-the-shelf equipment and uncovered flaws in typical assumptions underlying Wireless Sensor Network research. © 2011 IEEE.

  • 125.
    Bader, Sebastian
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Krämer, Matthias
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Oelmann, Bengt
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    A Domain-Specific Platform for Research in Environmental Wireless Sensor Networks2013In: SENSORCOMM 2013, The Seventh International Conference on Sensor Technologies and Applications / [ed] Sergey Yurish, IFSA - Barcelona, Spain Muhammad Shakeel Virk, Narvik University College, Norway, 2013, p. 200-207Conference paper (Refereed)
    Abstract [en]

    Wireless Sensor Networks have the ability to improve a multitude of existing application domains. These networks are built up from a number of sensor nodes with sensing, communication and processing capabilities and the performance of the networked system is defined by the performance of the node platform it is based on. In this paper, we present SENTIO-em, a hardware platform for research in the environmental monitoring application domain. Based on the application domain requirements, the architecture and implementation of SENTIO-em is optimized for environmental monitoring constraints, while it is sufficiently flexible to be reused for different applications within the domain. The architecture of the platform is presented and evaluated under both laboratory and different environmental conditions. The obtained results are compared to a number of existing node platforms, demonstrating that SENTIO-em provides high energy efficiency with increased processing performance, short state transition times, and low quiescent currents.

  • 126.
    Bader, Sebastian
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Krämer, Matthias
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Oelmann, Bengt
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    A Testbed for the Evaluation of Solar Energy Harvesting ArchitecturesManuscript (preprint) (Other academic)
  • 127.
    Bader, Sebastian
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Ma, Xinyu
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Oelmann, Bengt
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    On the Modeling of Solar-Powered Wireless Sensor Nodes2014In: Journal of Sensor and Actuator Networks, ISSN 2224-2708, Vol. 3, no 3, p. 207-223Article in journal (Refereed)
    Abstract [en]

    Solar energy harvesting allows for wireless sensor networks to be operated over extended periods of time. In order to select an appropriate harvesting architecture and dimension for its components, an effective method for the comparison of system implementations is required. System simulations have the capability to accomplish this in an accurate and efficient manner. In this paper, we evaluate the existing work on solar energy harvesting architectures and common methods for their modeling. An analysis of the existing approaches demonstrates a mismatch between the requirement of the task to be both accurate and efficient and the proposed modeling methods, which are either accurate or efficient. As a result, we propose a data-driven modeling method based on artificial neural networks for further evaluation by the research community. Preliminary results of an initial investigation demonstrate the capability of this method to accurately capture the behavior of a solar energy harvesting architecture, while providing a time-efficient model generation procedure based on system-level data.

  • 128.
    Bader, Sebastian
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Oelmann, Bengt
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    A concept for remotely reconfigurable solar energy harvesting testbeds2017In: Proceedings of IEEE Sensors, IEEE, 2017, p. 837-839Conference paper (Refereed)
    Abstract [en]

    Existing solar energy harvesting systems are typically evaluated with a single configuration. However, results on different harvester configurations are often desired in order to select the appropriate match to specific ambient conditions and application requirements. In this paper, we therefore present a concept for remotely reconfigurable solar energy harvesting testbeds, which allows for multiple harvester configurations to be evaluated with a single system deployment. We demonstrate that such a testbed can be implemented in an efficient manner by utilizing the benefits of wireless sensor networks, resulting in a scalable and flexible system with low power consumption. 

  • 129.
    Bader, Sebastian
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Oelmann, Bengt
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Concealing the complexity of node programming in wireless sensor networks2013In: Proceedings of the 2013 IEEE 8th International Conference on Intelligent Sensors, Sensor Networks and Information Processing: Sensing the Future, ISSNIP 2013, IEEE conference proceedings, 2013, p. 177-182Conference paper (Refereed)
    Abstract [en]

    There is a significant potential for Wireless sensor networks to be used as a general distributed measurement and monitoring system. The integration of computation, communication and sensing enables smart sensors to be built that can be adapted to a plethora of application requirements and allow for automated data collection throughout the network. However, the potential end users of this systems are domain experts, who usually do not possess the technical expertise to program, and thus operate, wireless sensor nodes, which prohibits the technology from becoming off-the-shelf equipment. In this paper, we present a method which enables the complexity of programming sensor nodes to be concealed in order to allow domain experts to use wireless sensor networks in basic applications without the requirement of technical assistance. We propose to use a computer-based specification entry, which generates a configuration parameter set to adjust the sensor node's application behavior. The method has been implemented in a proof-of-concept system and evaluated with test subjects who possess limited programming skills. The results show that users without any prior programming knowledge, or experience with embedded systems, are capable of configuring a sensor node according to a given application scenario within minutes.

  • 130.
    Bader, Sebastian
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Oelmann, Bengt
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Enabling battery-less wireless sensor operation using solar energy harvesting at locations with limited solar radiation2010In: Proceedings - 4th International Conference on Sensor Technologies and Applications, SENSORCOMM 2010, IEEE conference proceedings, 2010, p. 602-608Conference paper (Refereed)
    Abstract [en]

    Environmental monitoring applications demand wireless sensor networks to operate over a long period of time. Although energy consumption of these systems has been tremendously reduced, lifetime of sensor nodes is still limited by the capacity and lifetime of batteries used as energy sources. Energy harvesting, and in outdoor deployments particular, solar energy harvesting becomes a suitable way of powering wireless sensor nodes as their power consumption decreases. In this paper we address the feasibility of battery-less operation of wireless sensor nodes using solar energy harvesting at locations where the amount of solar radiation is severely limited and seasonal variations are large. We present two circuit architectures optimized for low energy leakage and evaluate their performance based on data gathered in a deployment during winter in Sundsvall, Sweden. We show that both architectures allow operation of sensor nodes even in the darkest period of the year. Furthermore comparisons between the two architecture designs are provided. © 2010 IEEE.

  • 131.
    Bader, Sebastian
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Oelmann, Bengt
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Short-term energy storage for wireless sensor networks using solar energy harvesting2013In: Networking, Sensing and Control (ICNSC), 2013 10th IEEE International Conference on, IEEE , 2013, p. 71-76Conference paper (Refereed)
    Abstract [en]

    Solar energy harvesting has become a common energy source for outdoor wireless sensor networks. To avoid the lifetime limitation of traditional secondary battery technologies in these systems, energy harvesting architectures with short-term energy storage can be chosen. These technologies offer long shelf-life and many recharge cycles, but can buffer for only short periods of time due to their small storage capacity. In this paper we present the analysis of two of these short-term energy storage devices, namely double layer capacitors and thin-film batteries. We present different harvesting architectures using these buffer elements and compare their advantages and disadvantages in relation to being used in low-power wireless sensor network applications. Experimental results show that both storage types are viable options for the intended application, each bringing their own strengths and weaknesses.

  • 132.
    Bader, Sebastian
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Oelmann, Bengt
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Brunig, M.
    Autonomous Systems Laboratory, ICT Centre, CSIRO, Brisbane, Australia.
    Challenges for RF two-way time-of-flight ranging in wireless sensor networks2012In: Proceedings - Conference on Local Computer Networks, LCN, IEEE conference proceedings, 2012, p. 908-916Conference paper (Refereed)
    Abstract [en]

    In applications where a priori determination of location is infeasible, node localization schemes are desirable, which allow the node to estimate its location during network operation. The majority of these schemes are based on ranging between node pairs, which should ideally be performed without adding cost or size to the sensor node. Two-way time-of-flight schemes can fulfill this desire, by utilizing the measurement of the time-of-flight of electromagnetic waves to determine the distance between two sensor nodes. In this paper, we present the implementation and analysis of such a ranging scheme. Because a small error in time measurement can result in a large distance estimation error, the focus of this work lies on the determination and analysis of influencing factors, which limit the accuracy of round-trip-time measurements. We analyze two main contributing factors to the accuracy of the ranging scheme, namely the radio transceiver clock quantization and the link quality during round-trip-time measurement. These effects and their impact on the overall ranging error have been investigated by means of simulation and experimentation. Initial ranging errors as large as 24 m RMS were observed, which could be reduced to errors between 5 and 8 m RMS by utilizing compensation techniques.

  • 133.
    Bader, Sebastian
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Schölzel, Torsten
    Solar Watt AG, Germany.
    Oelmann, Bengt
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    A Method for Dimensioning Micro-Scale Solar Energy HarvestingSystems Based on Energy Level Simulations2010In: Proceedings - IEEE/IFIP International Conference on Embedded and Ubiquitous Computing, EUC 2010, IEEE conference proceedings, 2010, p. 372-379Conference paper (Refereed)
    Abstract [en]

    Solar energy harvesting gains more and more attention in the field of wireless sensor networks. In situations, where these sensor systems are deployed outdoors, powering sensor nodes by solar energy becomes a suitable alternative to the traditional way of battery power supplies. Since solar energy, opposed to batteries, can be considered as an inexhaustible energy source, scavenging this source allows longer system lifetimes and brings wireless sensor networks closer to be an autonomous system with perpetual lifetime. Despite the possibility of designing and constructing these harvesting system, dimensioning becomes a crucial task to fit implemented components to application and load system demands. In this paper we present a way of dimensioning solar harvesting systems based on simulation. Method and implementation of component and system models are described on the basis of an example architecture that has been used in prior work. Furthermore we evaluate the model in comparison to deployment of the same architecture and show the suitability of using the simulation as a support to optimize choices for system parameters

  • 134.
    Bakar, Muhammad Abu
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Design and optimization of soft switched power converters for low and medium power applications2016Licentiate thesis, comprehensive summary (Other academic)
  • 135.
    Bakar, Muhammad Abu
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Alam, Farhan MuhammadMid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.Barg, SobhiMid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.Bertilsson, KentMid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Reconfigurable three state dc-dc power converter for the wide output range applications2019Conference proceedings (editor) (Refereed)
    Abstract [en]

    Improving the dc voltage gain of power converters has been the primary focus of the current and past research in the area of power electronics. This work presents another solution to widen the range of the output voltage. It proposes three reconfigurable steps for the output voltage. The range of the output voltage varies up to four times the base level. These configurations together vary the output voltage from 15 to 96 volts. A soft switched dc-dc power converter is built with the traditional topology of phase shifted full bridge converter along with improved characteristics. For better management of the transformer loss, a configuration of four transformers has been employed. The proportional gate drive approach is implemented to obtain four similar isolated blocks of the output voltage. This makes it possible to either configure these blocks all in series, parallel or in series/ parallel combination of two. The concept is verified in a low-profile prototype. The hardware is characterized up to the load power of 1kW for the input voltage of 400Vdc. The converter reports better efficiency over the complete range of output voltage.

  • 136. Bakar, Muhammad Abu
    et al.
    Alam, Farhan Muhammad
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Barg, Sobhi
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Moumita, Das
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Bertilsson, Kent
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Reconfigurable three state dc-dc power converter forthe wide output range applications2019In: IECON2019, Lisbon: IEEE, 2019Conference paper (Refereed)
    Abstract [en]

    Improving the dc voltage gain of power convertershas been the primary focus of the current and past research in thearea of power electronics. This work presents another solution towiden the range of the output voltage. It proposes threereconfigurable steps for the output voltage. The range of theoutput voltage varies up to four times the base level. Theseconfigurations together vary the output voltage from 15 to 96 volts.A soft switched dc-dc power converter is built with the traditionaltopology of phase shifted full bridge converter along withimproved characteristics. For better management of thetransformer loss, a configuration of four transformers has beenemployed. The proportional gate drive approach is implementedto obtain four similar isolated blocks of the output voltage. Thismakes it possible to either configure these blocks all in series,parallel or in series/ parallel combination of two. The concept isverified in a low-profile prototype. The hardware is characterizedup to the load power of 1kW for the input voltage of 400Vdc. Theconverter reports better efficiency over the complete range ofoutput voltage.

  • 137.
    Bakar, Muhammad Abu
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Alam, Farhan Muhammad
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Bertilsson, Kent
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    A phase shifted full bridge converter with novel control over the leakage inductance2016In: 2016 18TH EUROPEAN CONFERENCE ON POWER ELECTRONICS AND APPLICATIONS (EPE'16 ECCE EUROPE), Institute of Electrical and Electronics Engineers (IEEE), 2016, article id 7695545Conference paper (Refereed)
    Abstract [en]

    The electronics industry is progressing towards the high density board solutions due to the requirement of compact and intelligent electronic systems. In order to meet the industry demands, the power system is required to be of high power density. This article proposes one of the solution to improve the power density for the medium power applications. In phase shifted full bridge converter, the intrinsic leakage inductance of the main transformer is not high enough to obtain the zero voltage switching of the power switches for the entire operating conditions. An additional shim inductor is usually connected in series with the primary winding of the main transformer to increase the collective leakage inductance. This additional shim inductor degrades the power density of the converter. This paper proposes a method to embed and control the resonance inductance inside the main transformer. In addition to the increased inter-winding spacing, this paper proposes a practical approach to integrate the ferrite rods inside the main transformer for further increase in the leakage inductance. A power transformer is constructed and investigated by using the modelled equations to estimate the leakage inductance. A prototype phase shifted full bridge converter is also developed to investigate the performance of the proposed transformer. The converter is designed for the switching frequency of 400kHz, and tested up to 600watts output power at the input voltage of 200Vdc. The performance of the proposed converter is also compared with the converter of using an external inductor. The investigations show that, in addition to the improved power density, the converter with the proposed transformer is more efficient than the converter with the traditional transformer.

  • 138.
    Bakar, Muhammad Abu
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Bertilsson, Kent
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    An improved modelling and construction of power transformer for controlled leakage inductance2016In: Environment and Electrical Engineering (EEEIC), 2016 IEEE 16th International Conference on, IEEE, 2016Conference paper (Refereed)
    Abstract [en]

    In this work, a transformer with increased leakage inductance for the soft switched power applications is presented as a practical solution by constructing a transformer with good control over the leakage inductance. An analytical reluctance based model is presented, which accurately predicts the leakage inductance. With the presented approach, a transformer is designed with a leakage inductance varying between 3-7μH. Increasing the efficiency and improving the power density has been the main focus of power electronics researchers in the recent years. In this regards, transformers with increased leakage inductance are becoming more popular in order to accomplish different soft switching concepts and for improving the power density.

  • 139.
    Bakar, Muhammad Abu
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Bertilsson, Kent
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Ambatipudi, Radhika
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    High frequency (MHz) soft switched flyback dc-dc converter using GaN switches and six-layered PCB transformer2016In: IET Conference Publications, UK: Institution of Engineering and Technology, 2016, Vol. 2016, p. 1-6, article id CP684Conference paper (Refereed)
    Abstract [en]

    The increased switching losses with increasing switching frequency are the biggest concerns in designing high power density converters. This paper presents the investigation of an energy efficient DC-DC flyback converter in combination with six layered printed circuit board transformer. The recorded efficiency of the low profile transformer for the frequency range of 1-5MHz is 98% at power density of 770W/in3. The proposed converter is characterized for frequencies up to 4MHz by using possible soft switching techniques such as Boundary Mode and Quasi Resonant Mode. The emerging Gallium Nitride (GaN FET) devices are used as power switch. The control is incorporated with Digital Signal Processor (dsPIC) for both the Boundary and Quasi Resonant Modes of operations. The proposed flyback DC-DC converter is tested on a prototype Printed Circuit Board (PCB). The performance of the proposed converter is investigated for the telecom input voltage range of 36-72Vdc. The maximum obtained energy efficiency of the converter is about 94%. According to the authors' knowledge, this is the maximum efficiency ever achieved in flyback converters switching in MHz frequency range. The results are very encouraging for the development of high frequency, high power density and low cost isolated power converters.

  • 140. Ballabriga, R.
    et al.
    Blaj, G.
    Campbell, M.
    Fiederle, M.
    Greiffenberg, D.
    Heijne, E. H. M.
    Llopart, X.
    Plackett, R.
    Procz, S.
    Tlustos, L.
    Turecek, D.
    Wong, Winnie
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Characterization of the Medipix3 pixel readout chip2011In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 6, no 1Article in journal (Refereed)
  • 141. Ballabriga, R
    et al.
    Campbell, M
    Heijne, E H M
    Llopart Cudié, Xavier
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Tlustos, L
    The Medipix3 prototype, a pixel readout chip working in single photon counting mode with improved spectrometric performance2006In: procedings of Nuclear Science Symposium IEEE 2006, Ocotber 2006, San Diego USA, 2006Conference paper (Refereed)
  • 142. Ballabriga, R.
    et al.
    Campbell, M.
    Heijne, E.
    Llopart, X.
    Tlustos, L.
    Wong, Winnie
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Medipix3: A 64 k pixel detector readout chip working in single photon counting mode with improved spectrometric performance2011In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 633, no SUPPL. 1, p. S15-S18Article in journal (Refereed)
    Abstract [en]

    Medipix3 is a 256×256 channel hybrid pixel detector readout chip working in a single photon counting mode with a new inter-pixel architecture, which aims to improve the energy resolution in pixelated detectors by mitigating the effects of charge sharing between channels. Charges are summed in all 2×2 pixel clusters on the chip and a given hit is allocated locally to the pixel summing circuit with the biggest total charge on an event-by-event basis. Each pixel contains also two 12-bit binary counters with programmable depth and overflow control. The chip is configurable such that either the dimensions of each detector pixel match those of one readout pixel or detector pixels are four times greater in area than the readout pixels. In the latter case, event-by-event summing is still possible between the larger pixels. Each pixel has around 1600 transistors and the analog static power consumption is below 15 μW in the charge summing mode and 9 μW in the single pixel mode. The chip has been built in an 8-metal 0.13 μm CMOS technology. This paper describes the chip from the pixel to the periphery and first electrical results are summarized.

  • 143.
    Balliu, Enkeleda
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Andersson, Henrik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Engholm, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Forsberg, Sven
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Laser-assisted reduction of graphene oxide for paper based large area flexible electronics2016In: Proceedings of SPIE - The International Society for Optical Engineering, SPIE - International Society for Optical Engineering, 2016, Vol. 9736, article id 973610Conference paper (Refereed)
    Abstract [en]

    In this work we present a promising method for fabrication of conductive tracks on paper based substrates by laser assisted reduction of Graphene Oxide (GO). Printed electronics on paper based substrates is be coming more popular due to lower cost and recyclability. Fabrication of conductive tracks is of great importance where metal, carbon and polymer inks are commonly used. An emerging option is reduced graphene oxide (r-GO), which can be a good conductor. Here we have evaluated reduction of GO by using a 532 nm laser source, showing promising results with a decrease of sheet resistance from >100 M Ω/Sqr for unreduced GO down to 126 Ω/Sqr. without any observable damage to the paper substrates.

  • 144.
    Balliu, Enkeleda
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Andersson, Henrik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Engholm, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Öhlund, Thomas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Nilsson, Hans-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Selective laser sintering of inkjet-printed silver nanoparticle inks on paper substrates to achieve highly conductive patterns2018In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, no 1, article id 10408Article in journal (Refereed)
    Abstract [en]

    Development of cost-effective and environmentally friendly manufacturing methods will enable important advances for the production of large-scale flexible electronics. Laser processing has shown to be a promising candidate that offers a fast and non-destructive way to produce highly conductive patterns on flexible substrates such as plastics. However, an emerging option with a lower environmental impact is instead the use of cellulose-based flexible substrates, such as paper. In this work we investigate the use of laser sintering of silver nanoparticle inks, which were inkjet-printed on three different types of paper. Patterns with a high conductivity could be manufactured where a special care was taken to prevent the substrates from damage by the intense laser light. We found that the best results was obtained for a photopaper, with a conductivity of 1.63 107 S/m corresponding to nearly 26% of the bulk silver conductivity. In addition, we demonstrate laser sintering to fabricate a fully functional near field communication tag printed on a photopaper. Our results can have an important bearing for the development of cost-effective and environmentally friendly production methods for flexible electronics on a large scale. 

  • 145.
    Balliu, Enkeleda
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Andersson, Henrik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Engholm, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Laser sintering of silver nano-particles inks printed on paper substrates2015In: Proceedings of SPIE - The International Society for Optical Engineering, SPIE - International Society for Optical Engineering, 2015, p. Art. no. 935112-Conference paper (Refereed)
    Abstract [en]

    In this work we have investigated the use of laser sintering of different ink-jet printed nano-particle inks (NPIs) on paper substrates. Laser sintering is shown to offer a fast and non-destructive way to produce paper based printed electronics. A continuous wave fiber laser source at 1064 nm is used and evaluated in combination with a galvo-scanning mirror system. A conductivity in order of 2.16 ∗ 107 S/m is reached for the silver NPI structures corresponding to nearly 35 % conductivity compared to that of bulk silver and this is achieved without any observable damage to the paper substrate. © 2015 SPIE.

  • 146.
    Balliu, Enkeleda
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Engholm, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Hellström, J.
    Cobolt AB, SE-171 54 Solna, Sweden.
    Elgcrona, G.
    Cobolt AB, SE-171 54 Solna, Sweden.
    Karlsson, H.
    Cobolt AB, SE-171 54 Solna, Sweden.
    Compact nanosecond pulsed single stage Yb-doped fiber amplifier2014In: Proceedings of SPIE - The International Society for Optical Engineering, 2014, p. Art. no. 895910-Conference paper (Refereed)
    Abstract [en]

    In this work we present a compact, nanosecond pulsed, single frequency, single stage Yb-doped fiber amplifier by using an overall fiber core diameter of 20 μm. The key component is a custom made, compact, ultra-low noise, single frequency ring-cavity solid state laser (SSL) at 1064 nm used as a master oscillator. The SSL can be designed to provide nanosecond pulses with pulse energies in the sub-mJ range. Our ultimate goal is to develop a compact linearly polarized, single frequency, nanosecond pulsed laser source in an all-fiber format. Short (less than 1m), highly Yb-doped fibers have been used in order to suppress non-linear effects. © 2014 SPIE.

  • 147.
    Balliu, Enkeleda
    et al.
    Polytechnic of Turin.
    Massimo, Olivero
    Polytechnic of Turin.
    Andrea, Braglia
    Polytechnic of Turin.
    Alessio, Califano
    Polytechnic of Turin.
    Guido, Perrone
    Polytechnic of Turin.
    Pulsed thulium doped fiber laser at 1.94 μm based on a seed diode2013In: Proc. SPIE 8601, Fiber Lasers X: Technology, Systems, and Applications, 860133 (February 26, 2013) / [ed] Proc. SPIE, SPIE - International Society for Optical Engineering, 2013, Vol. 8601Conference paper (Other academic)
    Abstract [en]

    A fiber laser operating at 1.94μm in pulsed regime has been developed in a MOPA configuration. The seed consists of a custom-developed board hosting a laser diode, whose current is modulated to achieve the desired pulse shape, duration and repetition rate. The pulses are amplified through a thulium-doped fiber amplifier pumped at 793 nm. The design of the amplifier stage has been performed by dynamic simulation of a rate-equations model and compared to the experimental measurements. Simulations and experimental measurements have exhibited comparable results, devising the realization of an effective pulsed laser system whose parameters can be easily tuned through the seed. 

  • 148.
    Barac, Filip
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
    Caiola, Stefano
    Natl Instruments Italy, I-20090 Milan, Italy.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
    Sisinni, Emiliano
    Univ Brescia, Dept Informat Engn, I-25123 Brescia, Italy.
    Zhang, Tingting
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
    Channel Diagnostics for Wireless Sensor Networks in Harsh Industrial Environments2014In: IEEE Sensors Journal, ISSN 1530-437X, E-ISSN 1558-1748, Vol. 14, no 11, p. 3983-3995Article in journal (Refereed)
    Abstract [en]

    Wireless sensor network communication in industrial environments is compromised by interference, multipath fading, and signal attenuation. In that respect, accurate channel diagnostics is imperative to selecting the adequate countermeasures. This paper presents the lightweight packet error discriminator (LPED) that infers the wireless link condition by distinguishing between errors caused by multipath fading and attenuation, and those inflicted by interfering wideband single-channel communication systems (e.g., IEEE 802.11b/g), based on the differences in their error footprints. The LPED uses forward error correction in a novel context, namely, to determine the symbol error density, which is then fed to a discriminator for error source classification. The classification criteria are derived from an extensive set of error traces collected in three different types of industrial environments, and verified on a newly collected set of error traces. The proposed solution is evaluated both offline and online, in terms of classification accuracy, speed of channel diagnostics, and execution time. The results show that in ≥91% of cases, a single packet is sufficient for a correct channel diagnosis, accelerating link state inference by at least 270%, compared with the relevant state-of-the-art approaches. The execution time of LPED, for the worst case of packet corruption and maximum packet size, is below 30 ms with ≤3% of device memory consumption. Finally, live tests in an industrial environment show that LPED quickly recovers from link outage, by losing up to two packets on average, which is only one packet above the theoretical minimum.

  • 149.
    Barac, Filip
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
    Zhang, Tingting
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
    Channel Coding and Interleaving in Industrial WSN: Abiding to Timing Constraints and Bit Error Nature2013In: Proceedings - M and N 2013: 2013 IEEE International Workshop on Measurements and Networking, 2013, p. 46-51Conference paper (Refereed)
    Abstract [en]

    Forward Error Correction is a preemptive manner of improving communication reliability. Albeit not a part of IEEE 802.15.4-2006 standard, its application in Industrial Wireless Sensor Networks has been widely considered. Nevertheless, this study is the first performance analysis on real error traces with sufficiently lightweight channel codes, with respect to IEEE 802.15.4-2006 and industrial wireless communication timing constraints. Based on these constraints and bit error properties from the collected traces, the use of Reed-Solomon (15,7) block code is suggested, which can be implemented in software. Experiments show that bit error nature on links affected by multipath fading and attenuation in industrial environments is such that RS(15,7) can correct ≥95% of erroneously received packets, without the necessity for interleaving. On links under IEEE 802.11 interference, typically up to 50% of corrupted packets can be recovered by combining RS(15,7) with symbol interleaving, which has proven to be more effective than its bit counterpart. The optimal interleaving depth is found empirically and it is shown that simple bit-interleaved 1/3 repetition code achieves at least 90% of correcting performance of RS(15,7) code on uninterfered links that operate ≥10 dB above the sensitivity threshold.

  • 150.
    Barac, Filip
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
    Zhang, Tingting
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
    CLAP: Chip-Level Augmentation of IEEE 802.15.4 PHY for Error-Intolerant WSN Communication2015In: IEEE Vehicular Technology Conference, Glasgow, Scotland: IEEE Vehicular Technology Society , 2015, p. 1-7Conference paper (Refereed)
    Abstract [en]

    Communication reliability is the ultimate priority in safety-critical wireless sensor network (WSN) communication. Surprisingly enough, the enormous potential of error control on direct sequence spread spectrum (DSSS) chips in IEEE 802.15.4 has been completely overlooked by the WSN community, possibly due to incorrect presumptions, such as the concerns about computational overhead. Current error-correction schemes in WSN counteract the error process once the errors have already propagated to bit- and packet-level. Motivated by the notion that errors should be confronted at the earliest stage, this work presents CLAP, a novel method that tremendously improves the error correction in WSN by fortifying the IEEE 802.15.4 Physical layer (PHY) with straightforward manipulations of DSSS chips. CLAP is implemented on a software-defined radio platform, and evaluated on real error traces from heavily WLAN-interfered IEEE 802.15.4 transmissions at 3 different environments. CLAP boosts the number of corrected packets by 1.78-6.88 times on severely interfered links, compared to two other state-of-the-art schemes. The overhead in terms of computational complexity is about 10% of execution time of the OQPSK demodulator in the legacy IEEE 802.15.4 receiver chain.

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