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  • 101. Dai, D.
    et al.
    Liu, Liu
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Wosinski, L.ech
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Design and Fabrication of an Ultrasmall Overlapped AWG Demultiplexers Based on α-Si Nanowire Waveguides2006In: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 42, no 7, p. 400-402Article in journal (Refereed)
    Abstract [en]

    A novel layout for an ultra-compact arrayed-waveguide grating (AWG) demultiplexer is presented. The present layout has two overlapped free propagation regions, and is more compact than a conventional layout. Using αSi-on-SiO2 nanowire waveguides, an ultra-small 4×4 AWG (about 40×50 μm2) with channel spacing of 11 nm is fabricated and characterised.

  • 102.
    Dai, Daoxin
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Liu, Liu
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Three-dimensional hybrid modeling based on a beam propagation method and a diffraction formula for an AWG demultiplexer2007In: Optics Communications, ISSN 0030-4018, E-ISSN 1873-0310, Vol. 270, no 2, p. 195-202Article in journal (Refereed)
    Abstract [en]

    An efficient and accurate three-dimensional (3D) hybrid modeling, which combines a 3D beam propagation method (BPM) and the two-dimensional (2D) Kirchhoff-Huygens diffraction formula, is developed to simulate the field propagation in an arrayed waveguide grating (AWG) dernultiplexer. The 2D Kirchhoff-Huygens diffraction formula is used for the simulation of the light propagation in the free propagation regions (FPRs). A 3D BPM in a polar coordinate system is used to simulate the light propagation in the transition region between the input FPR and the arrayed waveguides so that the coupling coefficients for the arrayed waveguides are calculated conveniently and accurately. For the simulation in the transition region between the arrayed waveguides and the output FPR, only the central arrayed waveguide and several adjacent ones are needed in the computational window of a standard BPM and thus the computation efficiency is improved. Finally, a flat-top AWG is designed and fabricated to verify the reliability of the present simulation method. The calculated and measured spectral responses are in a good agreement.

  • 103. Dai, Daoxin
    et al.
    Liu, Liu
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Zhen, Sheng
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Design and fabrication of ultrasmall arrayed waveguide grating multiplexers based on Si nanowire waveguides2007In: Optoelectronics Letters, ISSN 1673-1905, Vol. 3, no 1, p. 7-9Article in journal (Refereed)
    Abstract [en]

    The large refractive index difference between Si and SiO2 makes it possible to realize ultrasmall photonic integrated circuits. A 5 × 5 ultracompact arrayed waveguide grating multiplexer based on 500×250 nm Si nanowire waveguides is designed and fabricated by using the technologies of E-beam writing and amorphous-Si deposition. The measured channel spacing is about 1.5 nm (close to the design value) and the channel crosstalk is about -8 dB.

  • 104.
    Dainese, Matteo
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Plasma assisted technology for Si-based photonic integrated circuits2005Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The last two decades have witnessed a large increase in capacity in telecommunication systems, thanks to the development of high bandwidth, fiber optic based networks. Nevertheless the continuing growth of Internet data traffic, fuelled by the development of numerous services like on-line commerce, video on demand, large audio/video files downloads, demands for a significant increase in the ability of the network nodes to manage incoming and outcoming data streams effectively and fast. The different functionalities that are needed include add/drop channel multiplexing, routing, signal reshaping and retiming, electrical/optical and optical/electrical conversion. This has stimulated a large effort towards the investigation of technologies for opto-electronic integration at a wafer level, in order to cope with all the required operations, while limiting overall costs. Among the different approaches proposed, one of the most promising is the “Silicon optical bench”, which relies on the well established VLSI technology for the microelectronics part and on planar lightwave circuits (PLCs) made either with silica-on-silicon waveguide technology (low index contrast) of amorphous silicon technology (high index contrast) on the integrated optics side.

    This thesis presents the development of new techniques and methodologies utilized in photonic device fabrication, which can be used to facilitate integration of temperature sensitive elements. The process is based on low temperature, plasma assisted, thick film deposition. First, a low temperature (300°C) deposition process based on Plasma assisted Chemical Vapour Deposition (PACVD) for the fabrication of silica based Planar Lightwave Circuits (PLC) is developed. The low thermal budget lends itself to monolithic integration with devices fabricated with different technologies. Absorption bands at around the wavelengths 1.48µm and 1.51µm caused by N-H and Si-H bonds within the material, respectively, had previously been thought to be intrinsic to the PACVD deposition method, when using N2O as oxidant gas of SiH4 and the other dopant precursors. The traditional method to eliminate these absorption bands was high temperature (>1000°C) annealing that seriously hinders device integration. An important achievement in this thesis is the improved suppression of these two absorption bands while keeping the whole fabrication temperature below 300°C and also having a high deposition rate. A complete fabrication process for silica planar lightwave circuits was also developed, by optimising the photolithography and etching step. Finally the effect of dopants like Ge and B on the optical properties of the deposited silica glass was investigated, with particular emphasis to the photosensitive properties of the material upon illumination in the near UV. UV trimming is shown to be a versatile method to selectively control polarization birefringence of devices. Transmission dips of above 50dB were achieved in photo-induced gratings in low temperature deposited B-Ge codoped waveguide cores, without the need for hydrogen loading or other sensitisation techniques. The application of a high refractive index like amorphous silicon is addressed for the realization of efficient Bragg reflectors, either as vertical cavity laser mirrors or as dispersive element for planar waveguides used in highly selective co-directional coupler filters. Applications of amorphous silicon as core material for photonic crystal devices are also shown. The investigations carried out in this thesis show that PACVD technology can provide low-loss and UV sensitive material suitable for realizing a variety of low cost integrated devices for future all optical networks.

  • 105.
    Dainese, Matteo
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Swillo, Marcin
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Wosinski, Lech
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Effects of process parameters on the photosensitivity properties of Ge doped silica films deposited with plasma CVD2005In: Proceedings of the 13th International Congress on Thin Films, 2005Conference paper (Refereed)
  • 106.
    Dainese, Matteo
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Swillo, Marcin
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Wosinski, Lech
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Spectroscopic investigation of the photosensitive properties of B-Ge codoped silica films2005In: Proceedings of the 13th International Congress on Thin Films, 2005Conference paper (Refereed)
  • 107.
    Dainese, Matteo
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Swillo, Marcin
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Wosinski, Lech
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Thylén, Lars
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Directional coupler wavelength selective filter based on dispersive  Bragg Reflection Waveguide2006In: Optics Communications, ISSN 0030-4018, E-ISSN 1873-0310, Vol. 260, no 2, p. 514-521Article in journal (Refereed)
    Abstract [en]

    A new type of wavelength selective filter, based on high differential dispersion between two coupled waveguides, is presented. The Bragg Reflection Waveguide displays high effective refractive index dispersion, due to the interaction of the guided mode with the two confining Bragg reflectors. When coupled with a weakly guided buried channel silica waveguide, a very narrow bandwidth filter (< 1 nm) can be easily produced, in a shorter length, with respect to directional couplers made with standard step index channel waveguides. The complete design methodology, fabrication and characterization are presented.

  • 108.
    Dam, Mads
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Regular SPKI2005In: Lecture Notes in Computer Science, ISSN 0302-9743, E-ISSN 1611-3349, Vol. 3364, p. 134-152Article in journal (Refereed)
    Abstract [en]

    SPKI is a certificate-based framework for authorisation in distributed systems. The SPKI framework is extended by an iteration construct, essentially Kleene star, to express constraints on delegation chains. Other possible applications, not explored in the paper, include multidomain network routing path constraints. The main decision problems for the extended language are shown to correspond to regular language membership and containment respectively. To support an efficient decision algorithm in both cases we give a sound and complete inference system for a fragment of the language which is decidable in polynomial time. We finally show how to use the extended syntax to represent constrained delegation in SPKI.

  • 109.
    Dam, Mads
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Stadler, Rolf
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    A Generic Protocol for Network State Aggregation2005Conference paper (Refereed)
    Abstract [en]

    Aggregation functions, which compute global parameters, such as the sum, minimum or average of local device variables, are needed for many network monitoring and management tasks. As networks grow larger and become more dynamic, it is crucial to compute these functions in a scalable and robust manner. To this end, we have developed GAP (Generic Aggregation Protocol), a novel protocol that computes aggregates of device variables for network management purposes. GAP supports continuous estimation of aggregates in a network where local state variables and the network graph may change. Aggregates are computed in a decentralized way using an aggregation tree. We have performed a functional evaluation of GAP in a simulation environment and have identied conguration choices that potentially allow us to control the performance characteristics of the protocol.

  • 110.
    Damola, Ayodele
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Peer to peer networking in Ethernet broadband access networks2005Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The use of peer-to-peer (P2P) applications is growing dramatically, particularly for sharing content such as video, audio, and software. The traffic generated by these applications represents a large proportion of Internet traffic. For the broadband access network providers P2P traffic presents several problems.

    This thesis identifies the performance and business issues that P2P traffic has on broadband access networks employing the McCircuit separation technique. A mechanism for managing P2P within the access network is proposed. The P2P diversion algorithm aims to manage P2P traffic within the access network based on layer 2 and layer 3 information without employing intrusive layer 7 traffic detection. To solve the contention problem experienced by best effort traffic in the access network, a solution based on the diversion algorithm and on a QoS based traffic classification scheme is proposed. A business model defining the business roles and pricing schemes is presented based on the features offered by the P2P diversion algorithm introducing new opportunities for gaining revenue from P2P traffic for the network service providers and providing better services to users.

  • 111.
    Danielsson, Erik
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Domeij, Martin
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Lee, Hyung-Seok
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Zetterling, Carl-Mikael
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Östling, Mikael
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Schöner, Adolf
    Acreo AB.
    Hallin, Christer
    Department of Physics and Measurement Technology, Linköping University.
    A 4H-SiC BJT with an Epitaxially Regrown Extrinsic Base Layer2005In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 483-485, p. 905-908Article in journal (Refereed)
    Abstract [en]

    4H-SiC BJTs were fabricated using epitaxial regrowth instead of ion implantation to form a highly doped extrinsic base layer necessary for a good base ohmic contact. A remaining p(+) regrowth spacer at the edge of the base-emitter junction is proposed to explain a low current gain of 6 for the BJTs. A breakdown voltage of 1000 V was obtained for devices with Al implanted JTE.

  • 112.
    Darko-Ampem, Sakyibea
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Katsoufi, M.
    Giambiagi, Pablo
    Swedish Institute of Computer Science, Sweden.
    Secure negotiation in virtual organizations2006In: Proceedings - 2006 10th IEEE International Enterprise Distributed Object Computing Conference Workshops, 2006Conference paper (Refereed)
    Abstract [en]

    Virtual organizations are dynamic associations of business partners that join forces to achieve a common goal. Because partners live in very competitive environments and they do not fully trust each other, they establish contractual agreements to help reduce the risk of participating in the virtual organization. This naturally puts severe demands on the security of the process leading to the establishment of a contract, including negotiation of terms and conditions. The open context in which virtual organizations are created raises further security concerns. This papers discusses the security requirements over contract negotiation that arise in this context, examines current negotiation protocols and proposes enhancements to one of them.

  • 113. de Rossi, S.
    et al.
    Sagnes, I.
    Legratiet, L.
    Talneau, A.
    Berrier, A.
    Mulot, M.
    Anand, Srinivasan
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Gentner, J. L.
    Longitudinal mode selection in constricted photonic crystal guides and electrically injected lasers2005In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 23, no 3, p. 1363-1368Article in journal (Refereed)
    Abstract [en]

    Locally reducing the width of a wide photonic crystal (PhC) waveguide generates a constriction which acts as an internal reflector. We have simulated and measured the spectral behavior of a wide PhC waveguide locally constricted to a narrower PhC waveguide and ended by two cleaved facets, thus generating two coupled cavities. Passive structures as well as electrically injected active structures have been investigated. The multimode behavior of wide PhC waveguides is evidenced to play a deciding role. Modal reflection and transmission at the constriction are simulated and measured on passive PhC waveguides, when varying the constrictions' hole size and length. The spectral behavior of full-PhC electrically pumped lasers including such a constriction is measured and analyzed according to the constriction geometry. Design rules are finally proposed to take advantage of this coupled-cavities behavior for high rejection and high external efficiency monomode laser operation.

  • 114.
    Dejanovic, Slavko
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Manufacture and characterization of elastic interconnection microstructures in silicone elastomer2006Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    The subject of this thesis is a new chip to substrate interconnection technique using self-aligning elastic chip sockets. This work was focused on the technology steps which are necessary to fulfill in order to realize the suggested technique. Elastic chip sockets offer a solution for several assembly and packaging challenges, such a thermo-mechanical mismatch, effortless rework, environmental compatibility, high interconnection density, high frequency signal integrity, etc.

    Two of the most challenging technology aspects, metallization and etching of the silicone elastomer were studied, but also, air bubble free casting of the silicone elastomer was taken into consideration. Elastic chip sockets and single elastic micro-bump contacts of different shapes and sizes were manufactured and characterized.

    The contact resistance measurements revealed that the elastic micro-bump contacts manufactured by using the developed methods require less than one tenth of the contact force to achieve the same low contact resistance as compared to commercial elastic interconnection structures.

    The analysis and measurements of the high frequency properties of the elastic micro-bump structures have shown that they can operate up to several tens of GHz without a serious degradation of the signal quality.

    The same methods were applied to manufacture very high density contact area array (approximately 80000 connections/cm2), which until now was achieved only using so called chip-first techniques.

    The low contact resistance, the absence of environmentally harmful materials, no need of soldering, easy rework as well as capability of very high interconnecting density and very high frequency compatibility, indicates a high potential of this technique for assembly and packaging.

    Moreover, the presented technology of the silicone elastomer micromachining (metallization and RIE in particular) can be used for manufacturing of other microstructures, like chemical or biological micro reactors.

  • 115.
    Dejanovic, Slavko
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Hesselbom, Hjalmar
    Norberg, Gunnar
    CF4/O2 versus SF6/O2 RIE of Silicon Elastomer: Characterization and ComparisonIn: IEEE transactions on components and packaging technologies (Print), ISSN 1521-3331, E-ISSN 1557-9972Article in journal (Other academic)
  • 116.
    Dejanovic, Slavko
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Hesselbom, Hjalmar
    Norberg, Gunnar
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Sputter Deposing of Chromium, Gold and Copper on Silicone ElastomerIn: IEEE transactions on components and packaging technologies (Print), ISSN 1521-3331, E-ISSN 1557-9972Article in journal (Other academic)
  • 117.
    Dejanovic, Slavko
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Norberg, Gunnar
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Hesselbom, Hjalmar
    Haglund, Daniel
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Metal Covered Elastic Micro-Bump Contacts as an Alternative to Commercial Elastic Interconnection TechniquesIn: IEEE transactions on components and packaging technologies (Print), ISSN 1521-3331, E-ISSN 1557-9972Article in journal (Other academic)
    Abstract [en]

    In this work, a novel chip-to-board interconnection structure have been manufactured, and some of its characteristics have been investigated. This chip connection technique can for instance serve as a FCOB (Flip Chip on Board) technique, for connecting test equipments during testing bare chip on wafer, and with some more development, in three dimensional multi chip modules. A setup of elastic micro-bumps was cast, metal covered, patterned, and electro-mechanically characterized. The metal-covered silicon elastomer contact-structures were manufactured on FR-4 carrier-plates. Visual inspection of the micro-bumps was conducted in a SEM (Scanning Electron Microscope). The electro-mechanical properties were measured by simultaneous use of a DMA (Dynamic Mechanical Analyzer) and a Kelvin Bridge structure for resistance measurement. The measurements gave the micro-bump to chip resistance behavior as a function of the micro-bump deflection distance and applied mechanical force when direct current was applied. The results obtained from the measurements have revealed that such a technique requires less than one tenth of the mechanical contact force for achieving the contact resistance of the same magnitude as for commercial elastic interconnection techniques. This would be of significant advantage because the amount of electrical contacts per unit of area has tendency of continued growth.

  • 118.
    Dejanovic, Slavko
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Norberg, Gunnar
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Olsson, Rickard
    Hesselbom, Hjalmar
    Manufacturing of Via Holes in Silicon ElastomerIn: IEEE transactions on components and packaging technologies (Print), ISSN 1521-3331, E-ISSN 1557-9972Article in journal (Refereed)
  • 119. Derakhshandeh, J.
    et al.
    Abdi, Y.
    Mohajerzadeh, S.
    Hosseinzadegan, H.
    Soleimani, E. A.
    Radamson, Henry
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Fabrication of 100 nm gate length MOSFET's using a novel carbon nanotube-based nano-lithography2005In: Materials Science & Engineering: B. Solid-state Materials for Advanced Technology, ISSN 0921-5107, E-ISSN 1873-4944, Vol. 124, p. 354-358Article in journal (Refereed)
    Abstract [en]

    PECVD-grown carbon nanotubes on (100)silicon substrates have been studied and exploited for electron emission applications. After the growth of vertical CNT's [Y. Abdi, J. Koohsorkhi, J. Derakhshandeh, S. Mohajerzadeh, H. Hosseinzadegan, M.D. Robertson, C. Benet, EMRS Spring Meeting, Strasbourg, France, May 2005] the grown nanotubes are encapsulated by means of an insulating TiO(2) layer, leading to beam-shape emission of electrons from the cathode towards the opposite anode electrode. The electron emission occurs using an anode-cathode voltage of 100 V with ability of direct writing on a photo-resist-coated substrates. Straight lines with widths between 50 and 200 nm have been successfully drawn. This technique has been applied on P-type (100)silicon substrates for the formation of the gate of N-MOSFET devices. The successful realization of MOSFET devices indicates its usefulness for applications in nano-electronic devices. This device has inversion Cox exceeding 0.7 mu F/cm(2), drive current equal to 3 10 mu A/mu m.

  • 120.
    Di Benedetto, Luigi
    et al.
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Kolahdouz, Mohammadreza
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Malm, B. Gunnar
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Östling, Mikael
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Radamson, Henry H.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Strain balance approach for optimized signal-to-noise ratio in SiGe quantum well bolometers2009In: ESSDERC 2009 - Proceedings of the 39th European Solid-State Device Research Conference, 2009, p. 101-104Conference paper (Refereed)
    Abstract [en]

    This work presents thermal and electrical characterization of SiGe/Si multi-quantum wells (MQWs) with different layer profiles in complete bolometer structures. The thermal property of the bolometers was studied by measuring thermal coefficient of resistivity (TCR) through I-V curves for five temperatures (25, 40, 55, 80 and 100°C) and for four different pixel areas. The results show a strong dependency of TCR on the Si/SiGe layer thickness and the presence of dopant impurity in the MQW. The noise measurements of MQWs were performed carefully by eliminating all external contributions and the noise spectroscopy provided the noise characteristic parameters. The results demonstrate that the noise depends on the geometric size of the MQW and it increases with decreasing of the pixel area. The investigations show the noise level in the bolometer structures is sensitive to any dopant segregation from the contact layers.

  • 121. Diaz, R. G.
    et al.
    Romero, J. L.
    Björk, Gunnar
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Bourennane, M.
    Certainty relations between local and nonlocal observables2005In: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 7Article in journal (Refereed)
    Abstract [en]

    We point out that for an arbitrary number of identical particles, each defined on a Hilbert space of arbitrary dimension, there exists a whole ladder of relations of complementarity between certain local and nonlocal measurements corresponding to every conceivable grouping of the particles, e. g., the more accurately we can know ( by a measurement) some joint property of three qubits ( projecting the state onto a tripartite-entangled state), the less accurate some other property, local to the three qubits, becomes. We investigate the relation between these complementarity relations and a similar relation based on interference visibilities. We also show that the complementarity relations are particularly tight for particles defined on prime dimensional Hilbert spaces.

  • 122.
    Dokoohaki, Nima
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Matskin, Mihhail
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Structural Determination of Ontology-Driven Trust Networks in Semantic Social Institutions and Ecosystems2007In: Proceedings of the International Conference on Mobile Ubiquitous Computing, Systems, Services and Technologies (UBICOMM'07) and the International Conference on Advances in Semantic Processing SEMAPRO, 2007, p. 263-268Conference paper (Refereed)
    Abstract [en]

    Social institutions and ecosystems are growing across the web and social trust networks formed within these systems create an extraordinary test-bed to study relation dependant notions such as trust, reputation and belief. In order to capture, model and represent the semantics of trust relationships forming the trust networks, main components of relationships are represented and described using ontologies. This paper investigates how effective design of trust ontologies can improve the structure of trust networks created and implemented within semantic web-driven social institutions and systems. Based on the context of our research, we represent a trust ontology that captures the semantics of the structure of trust networks based on the context of social institutions and ecosystems on semantic web.

  • 123.
    Domeij, Martin
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Danielsson, Erik
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Lee, Hyung-Seok
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Zetterling, Carl-Mikael
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Östling, Mikael
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Current gain of 4H-SiC bipolar transistors including the effect of interface states2005In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 483, p. 889-892Article in journal (Refereed)
    Abstract [en]

    The current gain (&beta;) of 4H-SiC BJTs as function of collector current (I-C) has been investigated by DC and pulsed measurements and by device simulations. A measured monotonic increase of &beta; with I-C agrees well with simulations using a constant distribution of interface states at the 4H-SiC/SiO2 interface along the etched side-wall of the base-emitter junction. Simulations using only bulk recombination, on the other hand, are in poor agreement with the measurements. The interface states degrade the simulated current gain by combined effects of localized recombination and trapped charge that influence the surface potential. Additionally, bandgap narrowing has a significant impact by reducing the peak current gain by about 50% in simulations.

  • 124.
    Domeij, Martin
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Lee, Hyung-Seok
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Danielsson, Erik
    Zetterling, Carl-Mikael
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Östling, Mikael
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Schöner, Adolf
    Acreo AB, Stockholm .
    Geometrical effects in high current gain 1100-V 4H-SiC BJTs2005In: IEEE Electron Device Letters, ISSN 0741-3106, E-ISSN 1558-0563, Vol. 26, no 10, p. 743-745Article in journal (Refereed)
    Abstract [en]

    This paper reports the fabrication of epitaxial 4H-SiC bipolar junction transistors (BJTs) with a maximum current gain beta = 64 and a breakdown voltage of 1100 V. The high beta value is attributed to high material quality obtained after a continuous epitaxial growth of the base-emitter junction. The BJTs show a clear emitter-size effect indicating that surface recombination has a significant influence on beta. A minimum distance of 2-3 mu m between the emitter edge and base contact implant was found adequate to avoid a substantial beta reduction.

  • 125.
    Domeij, Martin
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Lee, Hyung-Seok
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Zetterling, Carl-Mikael
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Östling, Mikael
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Schoner, A.
    Current gain dependence on emitter width in 4H-SiC BJTs2006In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 527-529, p. 1425-1428Article in journal (Refereed)
    Abstract [en]

    This paper reports the fabrication of epitaxial 4H-SiC bipolar junction transistors (BJTs) with a maximum current gain beta = 64 and a breakdown voltage of 1100 V. The high beta value is attributed to high material quality obtained after a continuous epitaxial growth of the base-emitter junction. The current gain of the BJTs increases with increasing emitter width indicating a significant influence of surface recombination. This "emitter-size" effect is in good agreement with device simulations including recombination in interface states at the etched termination of the base-emitter junction.

  • 126.
    Domeij, Martin
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Lee, Hyung-Seok
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Zetterling, Carl-Mikael
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Östling, Mikael
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Schöner, A.
    SiC power bipolar junction transistors: Modeling and improvement of the current gain2005In: 2005 European Conference on Power Electronics and Applications, Dresden, 2005, Vol. 2005, p. 1665888-Conference paper (Refereed)
    Abstract [en]

    Epitaxial silicon carbide bipolar junction transistors (BJTs) for power switching applications have been designed and fabricated with a maximum breakdown voltage of 1100 V. The BJTs have high common emitter current gains with maximum values exceeding 60, a result that is attributed to design optimization of the base and emitter layers and to a high material quality obtained by a continuous epitaxial growth. Device simulations of the current gain as function of collector current have been compared with measurements. The measurements show a clear emitter-size effect that is in good agreement with simulations including surface recombination in interface states at the etched termination of the base-emitter junction. Simulations indicate an optimum emitter doping around 1-1019 cm-3 in agreement with typical state-of-the-art BJTs.

  • 127.
    Dominique, Torkel
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Push services based on SIP2001Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The Session Initiation Protocol (SIP) is the most potential protocol for Real Time IP communication, for example IP telephony, today. This M.Sc. thesis project aim to create a solution for information providers to push information to a large numbers of users, using the SIP protocol and a number of proposed extensions to SIP. The system will be built on a SUBSCRIBE/NOTIFY mechanism similar to the one used for instant messages and presence. This system can be used for companies to build information push services (i.e. News, Traffic information, etc.) or to push commercial advertisement.

    The reason to use the SIP protocol for this is that SIP has already solved the addressing problem by introducing email-like addresses that follow the user when he moves around in the system. This is perfect for the push service that wants to reach the user wherever he is.

  • 128. Douheret, O.
    et al.
    Bonsels, S.
    Anand, Srinivasan
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Determination of spatial resolution in atomic-force-microscopy-based electrical characterization techniques using quantum well structures2005In: Journal of Vacuum Science & Technology B, ISSN 1071-1023, E-ISSN 1520-8567, Vol. 23, no 1, p. 61-65Article in journal (Refereed)
    Abstract [en]

    In this work, a procedure to determine the spatial resolution in scan ning capacitance (SCM) and scanning spreading resistance microscopy (SSRM) is proposed and demonstrated. It is based on profiling of confined carriers (in cross section) in quantum well (QW) structures consisting of QWs with different well widths and interwell spacing. Spatial resolution of sub-5 nm was observed for SSRM with commercially available diamond-coated silicon probes and sub-30 nm for SCM with IrPt5-coated probes. The influence of experimental parameters such as tip-sample bias and tip averaging on lateral resolution is discussed and appropriate measurement conditions for performing high-resolution measurements are highlighted. Finally, it is proposed that such structures can be used not only to select probes appropriate for high resolution measurements, but also in the development of new probes.

  • 129.
    Douheret, Oliver
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Maknys, Kestutis
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Anand, Sathyanarayan
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Electrical characterisation of III-V buried heterostructure lasers by scanning capacitance microscopy2005In: Scanning Probe Microscopy: Characterization, Nanofabrication and Device Application of Functional Materials / [ed] Vilarinho, PM; Rosenwaks, Y; Kingon, A, 2005, Vol. 186, p. 413-+Conference paper (Refereed)
    Abstract [en]

    In this work, cross-sectional scanning capacitance microscopy (SCM) is used to investigate GaAs/AlGaAs buried heterostructure (BH) lasers regrown with semi-insulating GaInP:Fe. The basic principles involved in the SCM methodology are first introduced, including resolution. The concept of doping contrast in SCM is experimentally demonstrated using InP doping staircase structure where in the doping in the different layers covers a reasonably wide dynamic range [similar to 10(18) cm(-3) to similar to 10(16) cm(-3)]. The capability of SCM to achieve complete electrical characterization of complex optoelectronic devices is then established using BH GaAs based lasers as an example. It is shown that a complete 2D map of the electrical properties of device structure, including delineation of regrown interfaces and the electrical nature of the regrown GaInP layer can be obtained. Characteristic peaks in the SCM signal (dC/dV) are seen at the interface between the regrown layers and the n-doped regions and attributed to band-bending at the interface. The behavior of the SCM signal with ac-bias is used to verify the semi-insulating nature of the regrown layer at different locations of the sample. The measured SCM signal for the regrown GaInP:Fe layer is uniformly zero indicating very low free carrier densities and confirms semi-insulating properties. This observation strongly suggests, in addition, uniform Fe incorporation in the regrown layers, close to and far away from the mesa. Finally, a nanoscale feature in the SCM contrast appearing as a bright spot in dC/dV mode is observed at the mesa sidewall close to the interface between the regrown GaInP:Fe and the p-barrier layer. The origin of this contrast is discussed in terms of local band-bending effects and supported by 2D Poisson simulations of the device structure.

  • 130.
    Drakenberg, N. Peter
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    A matrix-type for performance-portability: STATE OF THE ART IN SCIENTIFIC COMPUTING2006In: APPLIED PARALLEL COMPUTING: STATE OF THE ART IN SCIENTIFIC COMPUTING / [ed] Dongarra, J; Madsen, K; Wasniewski, J, BERLIN: SPRINGER-VERLAG BERLIN , 2006, Vol. 3732, p. 237-246Conference paper (Refereed)
    Abstract [en]

    When matrix computations are expressed in conventional programming languages, matrices are almost exclusively represented by arrays, but arrays are also used to represent many other kinds of entities, such as grids, lists, hash tables, etc. The responsibility for achieving efficient matrix computations is usually seen as resting on compilers, which in turn apply loop restructuring and reordering transformations to adapt programs and program fragments to target different architectures. Unfortunately, compilers are often unable to restructure conventional algorithms for matrix computations into their block or block-recursive counterparts, which are required to obtain acceptable levels of performance on most current (and future) hardware systems. We present a datatype which is dedicated to the representation of dense matrices. In contrast to arrays, for which index-based element-reference is the basic (primitive) operation, the primitive operations of our specialized matrix-type are composition and decomposition of/into submatrices. Decomposition of a matrix into submatrices (of unspecified sizes) is a key operation in the development of block algorithms for matrix computations, and through direct and explicit expression of (ambiguous) decompositions of matrices into submatrices, block algorithms can be expressed explicitly and at the same time the task of finding good decomposition parameters (i.e., block sizes) for each specific target system, is exposed to and made suitable for compilers.

  • 131.
    Drejhammar, Frej
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Schulte, Christian
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Haridi, Seif
    Brand, Per
    Flow Java: Declarative Concurrency for Java2003In: Proceedings of the Nineteenth International Conference on Logic Programming, 2003, Vol. 2916, p. 346-360Conference paper (Refereed)
  • 132. Driussi, F.
    et al.
    Esseni, D.
    Selmi, L.
    Hellström, Per-Erik
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Malm, B. Gunnar
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Hållstedt, Julius
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Östling, Mikael
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Grasby, T. J.
    Leadley, D. R.
    Mescot, X.
    On the electron mobility enhancement in biaxially strained Si MOSFETs2008In: Solid-State Electronics, ISSN 0038-1101, E-ISSN 1879-2405, Vol. 52, no 4, p. 498-505Article in journal (Refereed)
    Abstract [en]

    This paper reports a detailed experimental and simulation study of the electron mobility enhancement induced by the biaxial strain in (001) silicon MOSFETs. To this purpose, ad hoc test structures have been fabricated on strained Si films grown on different SiGe virtual substrates and the effective mobility of the electrons has been extracted. To interpret the experimental results, we performed simulations using numerical solutions of Schroedinger-Poisson equations to calculate the charge and the momentum relaxation time approximation to calculate the mobility. The mobility enhancement with respect to the unstrained Si device has been analyzed as a function of the Ge content of SiGe substrates and of the operation temperature.

  • 133.
    Dubrova, Elena
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Linear-time algorithm for computing minimum checkpoint sets for simulation-based verification of HDL programs2005In: 2005 IEEE International Symposium On Circuits And Systems (ISCAS), Conference Proceedings, IEEE , 2005, p. 2212-2215Conference paper (Refereed)
    Abstract [en]

    Simulation-based verification is a popular method for functional validation of hardware. It is performed by applying a set of tests to the system under consideration and to its reference model, and comparing the results. The effectiveness of a test suite is measured by the fraction of the system covered by the tests. In this paper, we present a technique for selecting a part of the system, called checkpoints, with the property that any set of tests which covers the checkpoints covers the entire system. Thus, by constructing a test suit for the checkpoints, a 100% coverage can be achieved. We present a linear-time algorithm for computing a minimum checkpoint set based on pre- and post-dominator relations of the control flow graph of the HDL program representing the system.

  • 134.
    Dubrova, Elena
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Modeling gene regulatory systems by random Boolean networks2005In: Bioengineered and Bioinspired Systems II / [ed] Carmona, RA; LinanCembrano, G, SPIE - International Society for Optical Engineering, 2005, Vol. 5839, p. 56-65Conference paper (Refereed)
    Abstract [en]

    A random Boolean network is a synchronous Boolean automaton with n vertices. The parameters of an RBN can be tuned so that its statistical features match the characteristics of the gene regulatory system. The number of vertices of the RBN represents the number of genes in tile cell. The number of cycles in the RBN's state space, called attractors, corresponds the number of different cell types. Attractor's length corresponds to the cell cycle time. Sensitivity of the attractors to different kind of perturbations, modeled by changing the state of a particular vertex, associated Boolean function, or network edge, reflects the stability of the cell to damage, mutations and virus attacks. In order to evaluate the attractors, their number and length have to be re-computed repeatedly. For large RBN's, searching for attractors in the O(2(n)) state space is an infeasible task. Fortunately, only a subset of vertices of an RBN, called relevant vertices, determines its dynamics. The remaining vertices are redundant. In this paper, we present an algorithm for identifying redundant vertices in RBNs which allows us to reduce the search space for computing at.tractors from O(2(n)) to Theta(2 root n). We also show how RBNs can be used for studying evolution.

  • 135.
    Dubrova, Elena
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Phylogenetic networks with edge-disjoint recombination cycles2005In: Bioengineered and Bioinspired Systems II / [ed] Carmona, RA; LinanCembrano, G, SPIE - International Society for Optical Engineering, 2005, Vol. 5839, p. 381-388Conference paper (Refereed)
    Abstract [en]

    Phylogenetic analysis is a branch of biology that establishes the evolutionary relationships between living organisms. The goal of phylogenetic analysis is to determine the order and approximate timing of speciation events in the evolution of a given set of species. Phylogenetic networks allow to represent evolutionary histories that include events like recombination and hybridization. In this paper, we introduce a class of phylogenetic networks called extended galled-trees in which recombination cycles share no edge. We show that the site consistency problem, which is NP-hard in general, can be solved in polynomial time for this class of phylogenetic networks.

  • 136.
    Dubrova, Elena
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Structural testing based on minimum kernels2005In: Proceedings -Design, Automation and Test in Europe, DATE '05 / [ed] Wehn, N; Benini, L, IEEE Computer Society, 2005, p. 1168-1173Conference paper (Refereed)
    Abstract [en]

    Structural testing techniques, such as statement and branch coverage, play an important role in improving dependability of software systems. However, finding a set of tests which guarantees high coverage is a time-consuming task. In this paper we present a technique for structural testing based on kernel computation. A kernel satisfies the property that any set of tests which executes all vertices (edges) of the kernel executes all vertices (edges) of the program's flowgraph. We present a linear-time algorithm for computing minimum kernels based on pre- and post-dominator relations of a flowgraph.

  • 137.
    Dubrova, Elena
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Teslenko, Maxim
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Compositional properties of random Boolean networks2005In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics, ISSN 1539-3755, E-ISSN 1550-2376, Vol. 71, no 5, p. 056116-Article in journal (Refereed)
    Abstract [en]

    Random Boolean networks (RBNs) are used in a number of applications, including cell differentiation, immune response, evolution, gene regulatory networks, and neural networks. This paper addresses the problem of computing attractors in RBNs. An RBN with n vertices has up to 2(n) states. Therefore, for large n, computing attractors by full enumeration of states is not feasible. The state space can be reduced by removing irrelevant vertices, which have no influence on the network's dynamics. In this paper, we show that attractors of an RBN can be computed compositionally from the attractors of the independent components of the subgraph induced by the relevant vertices of the network. The presented approach reduces the complexity of the problem from O(2(n)) to O(2(l)), where l is the number of relevant vertices in the largest component.

  • 138.
    Dubrova, Elena
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Teslenko, Maxim
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Martinelli, Andrés
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Kauffman networks: Analysis and applications2005In: ICCAD-2005: INTERNATIONAL CONFERENCE ON COMPUTER AIDED DESIGN, DIGEST OF TECHNICAL PAPERS, 2005, p. 479-484Conference paper (Refereed)
    Abstract [en]

    A Kauffman network is an abstract model of gene regulatory networks. Each gene is represented by a vertex. An edge from one vertex to another implies that the former gene regulates the latter. Statistical features of Kauffman networks match the characteristics of living cells. The number of cycles in the network's state space, called attractors, corresponds to the number of different cell types. The attractor's length corresponds to the cell cycle time. The sensitivity of attractors; to different kinds of disturbances, modeled by changing a network connection, the state of a vertex, or the associated function, reflects the stability of the cell to damage, mutations and virus attacks. In order to evaluate attractors, their number and lengths have to be computed. This problem is the major open problem related to Kauffman networks. Available algorithms can only handle networks with less than a hundred vertices. The number of genes in a cell is often larger. In this paper, we present a set of efficient algorithms for computing attractors in large Kauffman networks. The resulting software package is hoped to be of assistance in understanding the principles of gene interactions and discovering a computing scheme operating on these principles.

  • 139.
    Dubrova, Elena
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Teslenko, Maxim
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Tenhunen, Hannu
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Computing attractors in complex dynamic networks2005Conference paper (Refereed)
  • 140.
    Duo, Xinzhong
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    System-on-package solutions for multi-band RF front end2005Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Advances in microelectronics technology have enabled us to integrate a complex electronic system (such as a radio) on a single chip or in a single package module, known as system-on-chip (SoC) and system-on-package (SoP) paradigms. This brings not only new opportunities for system integration, but also challenges in design and implementation. One of these challenges is how to achieve an optimum total solution of system integration via chip and package co-design, because there is no tool or design methodology available for such kind of optimization. This thesis focuses on innovative multi-band multi-standard radio front-end design and explores a new design methodology. The motivation of developing this design methodology is to achieve an optimum total solution for radio system implementation via chip and package co-design and co-optimization.

    The methodology starts from RF packaging and components modeling. Necessary models for both on-chip and off-chip passives are developed. Parasitic effects of packages for radio chips are modeled for particular frequencies. Compared with high-speed digital packaging, RF packaging normally deals with narrow band signals. It is possible to absorb some unwanted parasitics by designing proper port matching networks. In addition, cost-performance trade-offs are performed. In this context, we first developed process and technology based cost models, which include parameters like chip real estate, raw materials, package, test and rework. Impact of process variation on final yield has also been considered in the models by using a statistical analysis approach. Performance of different design options is measured by a special FoM (figure-of-merit). Each type of analog/RF circuit (such as LNA, PA and ADC) has its own dedicated FoM. Through a series of cost-performance trade-offs for different on-chip versus off-chip passives and partitions, an optimum total solution is obtained.

    Finally, this methodology was demonstrated via a number of design examples for multi-band multi-standard radio front-end. The author has explored the optimum solutions for different circuit architectures and process technologies encompassing parallel, concurrent and digitally programmable multi-band radio frond-end blocks. It is interesting to find that, for complex RF circuits like a multi-band multi-standard radio, moving some passives off-chip will have significant cost-savings. In addition to the above contributions, the author has also developed an MCM-D technology on LCP and glass substrates, based on metal deposition and BCB spin-coating at KTH clean room. The author has also performed some preliminary studies on UWB radio for RFID applications.

  • 141.
    Duo, Xinzhong
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Zheng, Li-Rong
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Ismail, Muhammed
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Tenhunen, Hannu
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Broadband CMOS LNAs for IR-UWB receiver2005In: Norchip 2005, Proceedings, New York: IEEE , 2005, p. 273-276Conference paper (Refereed)
    Abstract [en]

    Two single-ended wideband LNAs for Ultrawide-band receiver have been designed and implemented in 0.18 mu m CMOS technology. The first one, a feed-back LNA, is a two-stage amplifier with a improved feedback loop, which provides high gain and enables the input port to match with 500 in a wide frequency range from 500MHz to 8GHz. The second one, an LC low-pass-filter matched LNA, employs a third-order low pass filter in the input port to match a frequency range from 3GHz to 8GHz. In both of the LNAs, the input stage is a common source amplifier. Inductive shunt peaking is used for maximizing the bandwidth and flatting the gain. In the feed-back LNA, measurements show that the maximum gain is 11.5dB, the 3-dB; bandwidth is from 500MHz to 7GHz, IIP3 is -2.2dBm at 4GHz, the minimum noise figure is around 5.7dB, S11 is less than 8.2dB, and the power consumption is 14mW. In the LC filter matched LNA, the 3-dB bandwidth is from 3GHz to 7.3GHz. The maximum gain is 9.6dB, IIP3 is 0dBm at 4 GHz, the minimum noise figure is 7.6dB, S11 is less than -13.4dB and the power consumption is 23mW.

  • 142.
    Eckerström, Johan
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Location Aware Communication2003Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Automotive telematic systems will be as common in future cars as ABS and airbags are in current cars. These systems will provide services such as navigation aid, automatic emergency alerts, traffic and road information, information about parking possibilities, tourist information, and personalized news. All these services need a communication link to the mobile Internet to be able to work properly. In this master’s thesis General Packet Radio Service, GPRS will be investigated and evaluated as a bearer for these kinds of services. A test application was built to test the location aware communication on the field. Upstream and downstream delays, possible bottlenecks in the network, connection set-up time, characteristics of different operators, and connection breakdowns where analyzed.

    The tests showed high network delays, and that many connection breakdowns occurred. The operators did not differ much when it comes to performance. One mayor drawback with GPRS is the low scalability with respect to operator’s lack of IP addresses, which will be discussed.

    Conclusions of the evaluation were that only certain location-based services are suitable over GPRS with the quality of today.

  • 143.
    Ekenberg, Ulf
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Gvozdic, D. M.
    Analysis of electric-field-induced spin splitting in wide modulation-doped quantum wells2008In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 78, no 20, p. 205317-Article in journal (Refereed)
    Abstract [en]

    We analyze the proper inclusion of electric-field-induced spin splittings in the framework of the envelope function approximation. We argue that the Rashba effect should be included in the form of a macroscopic potential as diagonal terms in a multiband approach rather than the commonly used Rashba term dependent on k and electric field. It is pointed out that the expectation value of the electric field in a subband is sometimes not unique because the expectation values can even have opposite signs for the spin-split subband components. Symmetric quantum wells with Dresselhaus terms and the influence of the interfaces on the spin splitting are also discussed. We apply a well established multiband approach to wide modulation-doped InGaSb quantum wells with strong built-in electric fields in the interface regions. We demonstrate an efficient mechanism for switching on and off the Rashba splitting with an electric field being an order of magnitude smaller than the local built-in field that determines the Rashba splitting. The implications of our findings for spintronic devices, in particular the Datta-Das spin transistor and proposed modifications of it, are discussed.

  • 144.
    Eklöf, Martin
    et al.
    Swedish Defence Research Agency (FOI).
    Ayani, Rassul
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Moradi, Farshad
    Swedish Defence Research Agency (FOI).
    Evaluation of a Fault-Tolerance Mechanism for HLA-Based Distributed Simulations2006In: 20th Workshop on Principles of Advanced and Distributed Simulation, PADS 2006: Singapore; 24 May 2006 through 26 May 2006, 2006, p. 175-182Conference paper (Refereed)
    Abstract [en]

    Successful integration of Modeling and Simulation (M&S) in the future Network-Based Defence (NBD) depends, among other things, on providing fault-tolerant (FT) distributed simulations. This paper describes a framework, named Distributed Resource Management System (DRMS), for robust execution of simulations based on the High Level Architecture. More specifically, a mechanism for FT in simulations synchronized according to the time-warp protocol is presented and evaluated. The results show that utilization of the FT mechanism, in a worst-case scenario, increases the total number of generated messages by 68% if one fault occurs. When the FT mechanism is not utilized, the same scenario shows an increase in total number of generated messages by 90%. Considering the worst-case scenario a plausible requirement on an M&S infrastructure of the NBD, the overhead caused by the FT mechanism is considered acceptable.

  • 145.
    Eklöf, Martin
    et al.
    Swedish Defence Research Agency (FOI), Dept. of Systems Modeling.
    Moradi, Farshad
    Swedish Defence Research Agency (FOI), Dept. of Systems Modeling.
    Ayani, Rassul
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    A framework for fault-tolerance in HLA-based distributed simulations2005In: Proceedings of the 2005 Winter Simulation Conference, 2005, p. 1182-1189Conference paper (Refereed)
    Abstract [en]

    The widespread use of simulation in future military systems depends, among others, on the degree of reuse and availability of simulation models. Simulation support in such systems must also cope with failure in software or hardware. Research in fault-tolerant distributed simulation, especially in the context of the High Level Architecture (HLA), has been quite sparse. Nor does the HLA standard itself cover fault-tolerance extensively. This paper describes a framework, named Distributed Resource Management System (DRMS), for robust execution of federations. The implementation of the framework is based on Web Services and Semantic Web technology, and provides fundamental services and a consistent mechanism for description of resources managed by the environment. To evaluate the proposed framework, a federation has been developed that utilizes time-warp mechanism for synchronization. In this paper, we describe our approach to fault tolerance and give an example to illustrate how DRMS behaves when it faces faulty federates.

  • 146. El Ghany, M. A. A.
    et al.
    El-Moursy, M. A.
    Ismail, Muhammed
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT. Electrical Engineering Dept., Ohio State University, United States .
    High throughput high performance NoC switch2008Conference paper (Refereed)
    Abstract [en]

    Increasing the number of virtual channels can improve the throughput in an on-chip interconnection network. High Throughput Butterfly Fat Tree (HTBFT) architecture to achieve high performance Networks on Chip (NoC) is proposed. The architecture increases the throughput of the network by 38% while preserving the average latency. The area of HTBFT switch is decreased by 18% as compared to Butterfly Fat Tree switch.

  • 147.
    El-Ansary, Sameh
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    A component-based P2P simulation environmentManuscript (preprint) (Other academic)
  • 148.
    El-Ansary, Sameh
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    A structured P2P overlay networks primerManuscript (preprint) (Other academic)
  • 149.
    El-Ansary, Sameh
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Designs and analyses in structured peer-to-peer systems2005Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Peer-to-Peer (P2P) computing is a recent hot topic in the areas of networking and distributed systems. Work on P2P computing was triggered by a number of ad-hoc systems that made the concept popular. Later, academic research efforts started to investigate P2P computing issues based on scientific principles. Some of that research produced a number of structured P2P systems that were collectively referred to by the term ``Distributed Hash Tables'' (DHTs). However, the research occurred in a diversified way leading to the appearance of similar concepts yet lacking a common perspective and not heavily analyzed. In this thesis we present a number of papers representing our research results in the area of structured P2P systems grouped as two sets labeled respectively ``Designs'' and ``Analyses''.

    The contribution of the first set of papers is as follows. First, we present the principle of distributed k-ary search (DKS) and argue that it serves as a framework for most of the recent P2P systems known as DHTs. That is, given the DKS framework, understanding existing DHT systems is done simply by seeing how they are instances of that framework. We argue that by perceiving systems as instances of the DKS framework, one can optimize some of them. We illustrate that by applying the framework to the Chord system, one of the most established DHT systems. Second, We show how the DKS framework helps in the design of P2P algorithms by two examples: (a) The DKS(n;k;f) system which is a system designed from the beginning on the principles of distributed k-ary search. (b) Two broadcast algorithms that take advantage of the distributed k-ary search tree.

    The contribution of the second set of papers is as follows. We account for two approaches that we used to evaluate the performance of a particular class of DHTs, namely the one adopting periodic stabilization for topology maintenance. The first approach was of an intrinsic empirical nature. In that approach, we tried to perceive a DHT as a physical system and account for its properties in a size-independent manner. The second approach was of a more analytical nature. In this approach we applied the technique of Master equations, which is a widely used technique in the analysis of natural systems. The application of the technique lead to a highly accurate description of the behavior of structured overlays.

    Additionally, the thesis contains a primer on structured P2P systems that tries to capture the main ideas that are prevailing in the field and enumerates a subset of the current hot and open research issues.

  • 150.
    El-Ansary, Sameh
    et al.
    Distributed Systems Laboratory, SICS Swedish Institute of Computer Science.
    Aurell, Erik
    KTH, School of Engineering Sciences (SCI), Physics.
    Haridi, Seif
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Physics-inspired performance evaluation of DHTsManuscript (preprint) (Other academic)
    Abstract [en]

    In the majority of structured peer-to-peer overlay networks a graph with a desirable topology is constructed. In most cases, the graph is maintained by a periodic activity performed by each node in the graph to preserve the desirable structure in face of the continuous change of the set of nodes. The interaction of the autonomous periodic activities of the nodes renders the performance analysis of such systems complex and simulation of scales of interest can be prohibitive. Physicists, however, are accustomed to dealing with scale by characterizing a system using intensive variables, i.e. variables that are size independent. The approach has proved its usefulness when applied to satisfiability theory. This work is the first attempt to apply it in the area of distributed systems. The contribution of this paper is two-fold. First, we describe a methodology to be used for analyzing the performance of large scale distributed systems. Second, we show how we applied the methodology to find two intensive variables that describe the characteristic behavior of the Chord overlay network, the variables are: 1) The density of nodes in the identifier space and 2) The ratio of the magnitude of perturbation of the network (joins/failures) to the magnitude of periodic stabilization of the network.

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