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  • 401. Liu, X. Y.
    et al.
    Holmström, Petter
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Jänes, Peter
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Thylén, Lars
    KTH, School of Information and Communication Technology (ICT).
    Andersson, T.G.
    Intersubband absorption at 1.5-3.5 µm in GaN/AlN multiple quantum wells grown by molecular beam epitaxy on sapphire2007In: Physica status solidi, ISSN 0370-1972, Vol. 244, no 8, p. 2892-2905Article in journal (Refereed)
    Abstract [en]

    Ten and twenty period multiple quantum well structures with 1.5-5.4 nm GaN wells and 1.2-5.1 nm AlN barriers were grown on sapphire by molecular beam epitaxy. Layer thicknesses were determined by X-ray diffraction measurements and simulations. Reciprocal space mapping showed that the relaxation of the quantum well layers was independent of the buffer layer thickness. Intersubband absorption was observed by Fourier transform infrared spectroscopy at λ ∼ 1.5-3.5 μm. Monolayer fluctuations in the quantum well width induced multiple peaks in spectra, which were well fitted to Lorentzian peaks of only 57 meV linewidth. Samples were very homogeneous as the absorption peak energy varied less than 1% along ∼4 cm on 2 inch wafers. The intersubband transition energies were calculated considering the conduction-band nonparabolicity, built-in fields, strain, and many-body effects. The calculation and comparison to the fitted Lorentzian peak energies indicated a moderate blueshift due to many-body effects. It was shown by both experiments and calculations that the AlN barrier width affects the intersubband transition energy.

  • 402. Liu, X. Y.
    et al.
    Janes, P.
    Holmstrom, P.
    Aggerstam, T.
    Lourdudoss, Sebastian
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Thylén, Lars
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Andersson, T. G.
    Growth of GaN and GaN/AlN multiple quantum wells on sapphire, Si and GaN template by molecular beam epitaxy2007In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 300, no 1, p. 79-82Article in journal (Refereed)
    Abstract [en]

    GaN layers of 280 nm thick were grown on sapphire, silicon (1 1 1) and GaN template by plasma assisted molecular beam epitaxy. From atomic force microscopy and high-resolution X-ray diffraction, it was found that GaN grown on sapphire and template gave smooth surface (RMS less then 0.5 nm) and very high crystalline quality (FWHM of (0 0 0 2) scan on sapphire only 48 arcsec). However, GaN growth on Si (1 1 1) provided rough surface and poor crystalline quality. The GaN/AlN multiple quantum well structures were grown on sapphire and template. Intersubband absorption spectra from Fourier transform infrared spectroscopy indicated that layers on GaN templates had better performances than on sapphire substrates.

  • 403. Liu, X.Y
    et al.
    Aggerstam, Thomas
    KTH, School of Information and Communication Technology (ICT), Material Physics, Semiconductor Materials, HMA.
    Jänes, Peter
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Holmström, Petter
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Lourdudoss, Sebastian
    KTH, School of Information and Communication Technology (ICT), Material Physics, Semiconductor Materials, HMA.
    Thylén, Lars
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Andersson, T. G.
    Investigation of intersubband absorption of GaN/AlN multiple quantum wells grown on different substrates by molecular beam epitaxy2007In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 301, no SPEC. ISS., p. 301-302Article in journal (Refereed)
    Abstract [en]

    Ten period GaN/AlN multiple quantum well (MQW) structures were grown by plasma-assisted molecular beam epitaxy (MBE) on sapphire substrates and metal-organic vapour-phase epitaxy (MOVPE)-grown GaN templates. Samples were investigated by high-resolution X-ray diffraction (HR-XRD) and Fourier transform infrared (FT-IR) spectroscopy. Intersubband (IS) absorbances and FWHM of IS absorption peaks indicated that samples grown on the GaN templates had better characteristics, resulting in a FWHM as low as 93 meV at a peak energy of 700 meV.

  • 404. Liu, Z. L.
    et al.
    Mei, Z. X.
    Zhang, T. C.
    Liu, Y. P.
    Guo, Y.
    Du, X. L.
    Hallén, Anders.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Zhu, J. J.
    Kuznetsov, A. Yu
    Solar-blind 4.55 eV band gap Mg0.55Zn0.45O components fabricated using quasi-homo buffers2009In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 311, no 18, p. 4356-4359Article in journal (Refereed)
    Abstract [en]

    A route for synthesizing high Mg content single-phase wurtzite MgZnO films having band gaps in the solar-blind region is demonstrated by employing molecular beam epitaxy on Al2O3 substrates. Importantly, a low Mg content "quasi-homo" buffer, Mg0.17Zn0.83O, was applied to accommodate a host of structural discrepancies and therefore, avoiding phase separation in a high Mg content film, Mg0.55Zn0.45O, as proved by X-ray diffraction. The Mg fraction in the overgrown single-phase epilayer, Mg0.55Zn0.45O, was confirmed by Rutherford backscattering spectrometry.

  • 405.
    Ljunggren, Daniel
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Entanglement in quantum communication: preparation and characterization of photonic qubits2006Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    At the heart of quantum physics lies the principle of superposition, and at the heart of information theory lies the bit. Perhaps the most useful property of quantum systems is that they can be loaded with information bits, so-called qubits, that are indefinitely both 0 and 1 until a measurement is made. Another consequence is that several qubits can become entangled, which is manifested by the non-classical correlations between such quantum systems when measured in all possible bases. Within the rapidly progressing fields of quantum information and quantum communication these quantum effects are utilized to perform tasks such as quantum computing and quantum cryptography.

    In this thesis we present experimental and theoretical work using single photon sources to prepare ``flying'' photonic qubits. We describe work using mainly quasi-phase-matched nonlinear crystals to generate beams of entangled photon pairs, that are either encoded in polarization at near-visible wavelengths, or in time at optical fiber telecommunication wavelengths (1550 nm). The optical fiber is the medium used for transporting the qubits over a long distance, and it is therefore essential to couple the photons well into the fibers. By focusing the beams optimally, we have investigated how this problem can meet the requirement of creating photons of a narrow frequency bandwidth and a high photon flux. Furthermore, we have generated truly single photons that are heralded by an electrical signal. As a result of modifying the statistics of such sources we have been able to show the effect of photon antibunching. In two separate works, we have implemented a quantum key distribution system based on faint laser pulses at the telecom wavelength of 1550 nm, as well as protocols based on entanglement for performing authentication of key distribution in quantum cryptography.

  • 406.
    Ljunggren, Daniel
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Tengner, Maria
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Optimal focusing for maximal collection of entangled narrow-band photon pairs into single-mode fibers2005In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 72, no 6, p. 062301-Article in journal (Refereed)
    Abstract [en]

    We present a theoretical and experimental investigation of the emission characteristics and the flux of photon pairs generated by spontaneous parametric downconversion in quasi-phase matched bulk crystals for the use in quantum communication sources. We show that, by careful design, one can attain well defined modes close to the fundamental mode of optical fibers and obtain high coupling efficiencies also for bulk crystals, these being more easily aligned than crystal waveguides. We distinguish between singles coupling, gamma(s) and gamma(i), conditional coincidence, mu(i vertical bar s), and pair coupling, gamma(c), and show how each of these parameters can be maximized by varying the focusing of the pump mode and the fiber-matched modes using standard optical elements. Specifically we analyze a periodically poled KTP-crystal pumped by a 532 nm laser creating photon pairs at 810 nm and 1550 nm. Numerical calculations lead to coupling efficiencies above 93% at optimal focusing, which is found by the geometrical relation L/z(R) to be approximate to 1 to 2 for the pump mode and approximate to 2 to 3 for the fiber-modes, where L is the crystal length and z(R) is the Rayleigh-range of the mode-profile. These results are independent on L. By showing that the single-mode bandwidth decreases proportional to 1/L, we can therefore design the source to produce and couple narrow bandwidth photon pairs well into the fibers. Smaller bandwidth means both less chromatic dispersion for long propagation distances in fibers, and that telecom Bragg gratings can be utilized to compensate for broadened photon packets-a vital problem for time-multiplexed qubits. Longer crystals also yield an increase in fiber photon flux proportional to root L, and so, assuming correct focusing, we can only see advantages using long crystals.

  • 407.
    Ljunggren, Daniel
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Tengner, Maria
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Marsden, Philip
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Pelton, Matthew
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Theory and experiment of entanglement in a quasi-phase-matched two-crystal source2006In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Phys. Rev. A, ISSN 1050-2947, Vol. 73, no 3, p. 032326-Article in journal (Refereed)
    Abstract [en]

    We report results regarding a source of polarization entangled photon pairs created by the process of spontaneous parametric downconversion in two orthogonally oriented, periodically poled, bulk KTiOPO4 crystals. The source emits light colinearly at the nondegenerate wavelengths of 810 and 1550 nm, and is optimized for a single-mode optical fiber collection and long-distance quantum communication. The configuration favors long crystals, which promote a high photon-pair production rate at a narrow bandwidth, together with a high pair probability in fibers. The quality of entanglement is limited by chromatic dispersion, which we analyze by determining the output state. We find that such a decoherence effect is strongly material dependent, providing for long crystals an upper bound on the visibility of the coincidence fringes of 41% for KTiOPO4, and zero for LiNbO3. The best obtained raw visibility, when canceling decoherence with an extra piece of crystal, was 91 +/- 0.2%, including background counts. We confirm by a violation of the CHSH-inequality (S=2.679 +/- 0.004 at 55 s(-1/2) standard deviations) and by complete quantum state tomography that the fibers carry high-quality entangled pairs at a maximum rate of 55x10(3) s(-1) THz(-1) mW(-1).

  • 408. Lo, Ikai
    et al.
    Gau, M. H.
    Tsai, J. K.
    Chen, Y. L.
    Chang, Z. J.
    Wang, W. T.
    Chiang, J. C.
    Aggerstam, T.
    Lourdudoss, Sebastian
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Anomalous k-dependent spin splitting in wurtzite AlxGa1-xN/GaN heterostructures2007In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 75, no 24Article in journal (Refereed)
    Abstract [en]

    We have observed the k-dependent spin splitting in wurtzite AlxGa1-xN/GaN heterostructures. An anomalous beating pattern was observed in Shubnikov-de Haas measurements due to the interference of Rashba and Dresselhaus spin-orbit interactions. The dominant mechanism for the k-dependent spin splitting at high values of k is attributed to Dresselhaus term which is enhanced by the Delta(C1)-Delta(C3) coupling of wurtzite band folding effect. The interference of Rashba and Dresselhaus effects in the AlxGa1-xN/GaN heterostructure provides a potential candidate for the gate-controlled spin-polarized spintronic devices.

  • 409.
    Lourdudoss, Sebastian
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT. KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP. KTH, School of Information and Communication Technology (ICT), Material Physics, Semiconductor Materials, HMA.
    Kjebon, Olle
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT. KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP. KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT. KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Nilsson, Stefan
    Stålnacke, Björn
    Fabrication and analysis of directly modulated 1.55 µm semiconductor lasers of bandwidth up to 30 GHz1997In: 4th Annual meeting of European Research Network of Excellence on the Physics and Technology of Mesoscopic Systems (Phantoms), March 1997, Aachen, Germany, paper D2.11., 1997Conference paper (Refereed)
  • 410.
    Lourdudoss, Sebastian
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT. KTH, School of Information and Communication Technology (ICT), Centres, Electrum Laboratory, ELAB.
    Olsson, Fredrik
    KTH, School of Information and Communication Technology (ICT), Centres, Electrum Laboratory, ELAB.
    Barrios, C. A.
    Hakkarainen, Teppo
    KTH, School of Information and Communication Technology (ICT), Centres, Electrum Laboratory, ELAB.
    Berrier, Audrey
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Anand, Srinivasan
    KTH, School of Information and Communication Technology (ICT), Centres, Electrum Laboratory, ELAB. KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Aubert, Amandine
    KTH, School of Information and Communication Technology (ICT), Centres, Electrum Laboratory, ELAB.
    Berggren, Jesper
    KTH, School of Information and Communication Technology (ICT), Centres, Electrum Laboratory, ELAB. KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Broeke, R. G.
    Cao, J.
    Chubun, N.
    Seo, S. -W
    Baek, J. -H
    Aihara, K.
    Pharn, Anh-Vu
    Ben Yoo, S. J.
    Avella, M.
    Jimenez, J.
    Heteroepitaxy and selective epitaxy for discrete and integrated devices2006In: 2006 CONFERENCE ON OPTOELECTRONIC AND MICROELECTRONIC MATERIALS & DEVICES, NEW YORK: IEEE , 2006, p. 309-311Conference paper (Refereed)
    Abstract [en]

    We present first results on heteroepitaxy of InP on silicon on insulator (SOI). We also demonstrate InP nanopillar fabrication by means of selective epitaxy. Selective epitaxy is also exploited to fabricate advanced photonic integrated devices for Optical Code Division Multiplex Access (OCDMA) networking applications.

  • 411.
    Lu, Zhonghai
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Using wormhole switching for networks on chip: feasibility analysis and microarchitecture adaptation2005Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Network-on-Chip (NoC) is proposed as a systematic approach to address future System-on-Chip (SoC) design difficulties. Due to its good performance and small buffering requirement, wormhole switching is being considered as a main network flow control mechanism for on-chip networks. Wormhole switching for NoCs is challenging from NoC application design and switch complexity reduction.

    In a NoC design flow, mapping an application onto the network should conduct a feasibility analysis in order to determine whether the messages’ timing constraints can be satisfied, and whether the network can be efficiently utilized. This is necessary because network contentions lead to nondeterministic behavior in message delivery. For wormhole-switched networks, we have formulated a contention tree model to accurately capture network contentions and reflect the concurrent use of links. Based on this model, the timing bounds of real-time messages can be derived. Furthermore, we have developed an algorithm to test the feasibility of real-time messages in the networks.

    From the wormhole switch micro-architecture level, switch complexity should be minimized to reduce cost but with reasonable performance penalty. We have investigated the flit admission and flit ejection problems that concern how the flits of packets are admitted into and ejected from the network, respectively. For flit admission, we propose a novel coupling scheme which binds a flit-admission queue with an output physical channel. Our results show that this scheme achieves a reduction of up to 8% in switch area and up to 35% in switch power over other comparable solutions. For flit ejection, we propose a p-sink model which differs from a typical ideal ejection model in that it uses only p flit sinks to eject flits instead of p • v flit sinks as required by the ideal model, where p is the number of physical channels of a switch and v is the number of virtual channels per physical channel. With this model, the buffering cost of flit sinks only depends on p, i.e., is irrespective of v. We have evaluated the coupled flit-admission technique and p-sink model in a 2D 4 x 4 mesh network. In our experiments, they exhibit only limited performance penalties in some cases. We believe that these cost-effective models are promising candidates to be used in wormhole-switched on-chip networks.

  • 412.
    Lu, Zhonghai
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Jantsch, Axel
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Sander, Ingo
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Feasibility analysis of messages for on-chip networks using wormhole routing2005In: PROCEEDINGS OF THE ASIA AND SOUTH PACIFIC DESIGN AUTOMATION CONFERENCE, VOLS 1 AND 2, IEEE conference proceedings, 2005, p. 960-964Conference paper (Refereed)
    Abstract [en]

    The feasibility of a message in a network concerns if its timing property can be satisfied without jeopardizing any messages already in the network to meet their timing properties. We present a novel feasibility analysis for real-time (RT) and non-realtime (NT) messages in wormhole-routed networks on chip. For RT messages, we formulate a contention tree that captures contentions in the network. For coexisting RT and NT messages, we propose a simple bandwidth partitioning method that allows us to analyze their feasibility independently.

  • 413.
    Lu, Zhonghai
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Sander, Ingo
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Jantsch, Axel
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Refinement of A Perfectly Synchronous Communication Model onto Nostrum NoC Best-Effort Communication Service2005In: Proceedings of the Forum on Design Languages, 2005Conference paper (Refereed)
  • 414. Luo, L.
    et al.
    Li, Z.
    Li, Shou
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    DFG model of real time character for instruments designed with embedded system2007In: 2007 8th International Conference on Electronic Measurement and Instruments, ICEMI, IEEE , 2007, p. 4830-4833Conference paper (Refereed)
    Abstract [en]

    A modeling method for analyzing the real time character of the instruments design with embedded technology was addressed in this paper. Analyzing and verifying of real time property in the instruments with embedded technology design is a crucial challenge. An analog and digital co-analysis method was given after the discussion for describing the real time property of an embedded system with time factors' set. And also, the data flow graph (DFG) is used in the modeling processing. At last of the paper, it is shown that the real time model could be used in mixed-signal SoC design.

  • 415. Luo, L.
    et al.
    Li, Z.
    Li, Shuo
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Consistency testing of IP in mixed-signal SoC2007In: 2007 8th International Conference on Electronic Measurement and Instruments, ICEMI, IEEE , 2007, p. 265-268Conference paper (Refereed)
    Abstract [en]

    Based on the discussion, on the consistency description method used for SoC design, the testing method about the operation consistency of IP (Intellectual Property) blocks is addressed in this paper. The method proposed the guidance for designing the test vectors in mixed signal SoC design. With the method, logical description of operation consistency specification can be built in SoC design. This paper indicates that operation consistency design is a key point and will impact both architecture of hardware and software.

  • 416. Luo, L.
    et al.
    Li, Z.
    Zhao, J.
    Li, Shuo
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Safety model of on-line electronic instrument based on embedded system2006In: 2006 8th International Conference on Signal Processing: Volume 4, IEEE , 2006, p. 3249-3252Conference paper (Refereed)
    Abstract [en]

    The safety model of electronics instrument and circuit control over Internet or local network is built in this paper. In industrial area, to keep instrument and circuit in safety is very important. Safety problem is discussed in detail as the base of safety problem description. The safety problem is summarized as denying dangerous operation of executing rules of control commands. A model for the commands executing relation and sequence is built in this paper. To build the model, the executing conditions for each command should be established at first. Based on the executing conditions the relation of different commands could be built. The safety model can be used for the operation safety checking. This model and safety problem description method also can be used for electronic instrument and circuit with embedded architecture.

  • 417. Lysak, V. V.
    et al.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP. KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Shulika, A. V.
    Sukhoivanov, I. A.
    Influence of gain nonlinearity on the second order harmonic distortion in semiconductor lasers2003In: Laser and Fiber-Optical Networks Modeling, 2003. Proceedings of LFNM 2003. 5th International Workshop on, 2003, p. 236-238Conference paper (Refereed)
    Abstract [en]

    The semiconductor laser is commonly used as a light source in fiber-optical telecommunication systems. In order to be able to send as much information as possible in a short time, it is important that the laser has a large modulation bandwidth, i.e., the turn-on and turn-off time should be as short as possible. In analogue fiber optic systems for transmission of radio or television signals, it is also important that the light from the laser increases linearly with driving current. Otherwise, the transmitted signal will become distorted. The modulation bandwidth and the modulation distortion are dependent both on the laser structure and the gain characteristics of the active material. In order to develop a correct laser model for calculation of, e.g., distortion one need an accurate model of the dependence of gain on carrier and photon density. We show that different gain models, fitted to give exactly the same modulation response can have significantly different distortion behavior.

  • 418.
    Magnusson, Håkan
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Olsson, Håkan
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    A cross-coupled dual-loop feedback power amplifier driver2005In: Proceedings of the 2005 European Conference on Circuit Theory and Design, 2005, p. 309-312Conference paper (Refereed)
    Abstract [en]

    This paper presents a wide-band power amplifier (PA) driver with matched output. A dual-loop cross-coupled feedback is applied on a simple two stage core amplifier. The use of a dual-loop feedback provides a broad-band 50 Ω output match without the use of any area consuming matching networks. The PA driver exhibits a gain higher than 6.4 dB, more than +1.9dBm 1-dB compression point with S22 less than -22 dB at the output, while dissipating 42 mA from a 1.8V supply. The output IP3 is better than +13.9 dBm at 2.4 GHz.

  • 419.
    Magnusson, Håkan
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Olsson, Håkan
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    A cross-coupled dual-loop feedback power amplifier drivier2005In: Proceedings of the 2005 European Conference on Circuit Theory and Design, Vol 3 / [ed] ORegan, F; Wegemer, C, 2005, p. 309-312Conference paper (Refereed)
    Abstract [en]

    This paper presents a wide-band power amplifier (PA) driver with matched output. A dual-loop cross-coupled feedback is applied on a simple two stage core amplifier. The use of a dual-loop feedback provides a broad-band 50 Omega output match without the use of any area consuming matching networks. The PA driver exhibits a gain higher than 6.4 dB, more than +1.9dBm 1-dB compression point with S22 less than -22 dB at the output, while dissipating 42 mA from a 1.8V supply. The output IP3 is better than +13.9 dBm at 2.4 GHz.

  • 420.
    Magnusson, Håkan
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Olsson, Håkan
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Multiband multi-standard transmitter using a compact power amplifier driver2005In: 2005 IEEE Radio Frequency Integrated Circuits (RFIC) Symposium, Digest of Papers / [ed] Jerng, A, NEW YORK, NY: IEEE , 2005, p. 491-494Conference paper (Refereed)
    Abstract [en]

    This paper presents a multistandard transmitter solution using a new power amplifier (PA) driver [1] operating in the broadcast, mobile, and the 2&5 GHz ISM bands. The use of dual-loop feedback in the driver provides a matched output without area consuming matching networks. The circuit size is as small as 0.3 mm(2) for the used 0.18 mu m CMOS process, saving about 0.7 mm(2) silicon area. Measurement results show a gain higher than 7.8 dB with a maximum output power of +4 dBm for all bands and using a supply voltage of 1.8V.

  • 421.
    Mahdavi, Adrian
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Value Added Services and Content Platforms2003Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Value-Added Services and Content Platforms (VAS and Content platforms) was carried out with in a group with same name at Tele2 AB in Kista, Stockholm. This group is responsible for network design, capacity planning, dimensioning, Acceptance testing (ATP test), and introducing of new functionality in Tele2's VASplatforms. Acceptance testing is performed on new devices (servers and other network components) in order to verify their capacity and performance guaranteed by their manufactures. Every platform has a guaranteed upper bound performance (based on the license a buyer has paid for), measured by different approaches. For instance for Short Message Service Center (SMSC) platforms, the measurement is based on the maximum number of SMS messages processed per second (SMS/sec), for Multimedia Messaging Service Center (MMSC) platforms the metric is the maximum number of MMS messages processed per second (MMS/sec), and for WAP Gateways it is the maximum number of WAP Transactions Per Second (TPS).

    This M.Sc. thesis project involved creating two graphical load generators for load testing of SMSC and MMSC platforms. These application-programs are not allowed to occupy unnecessary resources, or cause additional traffic on the radio network (when they are deployed), but they must be powerful enough in order to send and receive traffic in order to derive statistical data about the system's performance. This data will be used for behavioral analysis of these systems, and finally for verifying the guaranteed capacities. These tests are very important and decisive for service providers, who want to be able to offer good quality of service, guarantee availability, and offer reliability.

    In order to measure the performance and verify the guaranteed performance, two main scenarios were of great importance:

    • Sending 5 messages per second during a interval of 5 minutes. This case will simulate a TV-contest in which the TV audiences submit messages to a predefined number in order to join the contest.
    • Sending 3 Multimedia Messages per second during 30 minutes (for the MMSC performance measurement), and 7 SMS-messages per second during 120 minutes (for the SMSC performance measurement). This case attempts to simulate the traffic that will be generated in the minutes before and after Christmas or New Year.

    For behavioral analysis and performance measurement of the MMSC and the SMSC platforms an Open Queueing Network model is employed. In this model each server system is considered as a network, consisting of nodes, where each node represents one component inside the system. By considering each node as a single-server queueing system we can take advantage of queueing theory in order to drive several performance results.

  • 422. Maitra, M.
    et al.
    Bhattacharjee, P. S.
    Saha, D.
    Mukherjee, Amitava
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT. IBM Global Services India.
    Esakkiappan, C.
    An intelligent location management strategy for next generation wireless networks: A rule base approach2005In: 2005 IEEE Wireless Communications and Networking Conference: WCNC 2005: Broadband Wirelss for the Masses - Ready for Take-off, IEEE Communications Society, 2005, p. 1365-1370Conference paper (Refereed)
    Abstract [en]

    This work proposes an integrated location management scheme, which essentially rests on our previous work in which we proposed a novel Rule-Based Paging Scheme (RBPS) for reducing the cost for terminal paging in a cellular wireless environment The present work is an enhancement, where we extend our previous work to propose a complete location management scheme. This requires application of RBPS together with a judicious movement based location update (LU) scheme. Numerical results show that proposed integrated location management scheme, which we call, RBPS*, not only attempts to resolve the issue of inherent tradeoff between the cost components, comprising of paging and LU cost, it does reduce the total cost for location management compared to the other schemes referred in this work. RBPS* significantly outperforms RBPS and GSM-adopted blanket paging scheme along with movement based LU. When compared with the popular Shortest Distance First (SDF) scheme, results are again encouraging. The proposed scheme, RBPS*, is a generic one and can be deployed on-line. It has the potential for use in next generation wireless networks, irrespective of any standards.

  • 423. Maitra, M.
    et al.
    Saha, D.
    Bhattacharjee, P. S.
    Mukherjee, Amitava
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT. IBM Global Services India, India .
    Real time implementations aspects of an intelligent rule based paging scheme2005In: 2005 IEEE International Conference on Personal Wireless Communications, IEEE , 2005, p. 379-383Conference paper (Refereed)
    Abstract [en]

    In our earlier work we proposed a novel rule-based approach for locating a mobile terminal (MT) in a mobile cellular wireless networks. The scheme, which we called Rule-Based Paging Scheme (RBPS), significantly outperformed GSM-adopted blanket paging scheme. We have found that when compared with the popular Shortest Distance First (SDF) scheme, results are again encouraging. However, in this work, we have discussed the real time implementation of our proposed scheme and compared performance of the RBPS-adopted blanket paging scheme with GSM-adopted blanket paging scheme, as it is most popularly practiced in real life. The scheme is a generic one and has the potential for use in the next generation wireless networks, irrespective of any standards.

  • 424. Maitra, Madhubanti
    et al.
    Saha, Debashis
    Bhattacharjee, Partha Sarathi
    Mukherjee, Amitava
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    An intelligent paging strategy using rule-based AI technique for locating mobile terminals in cellular wireless networks2008In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 57, no 3, p. 1834-1845Article in journal (Refereed)
    Abstract [en]

    This paper proposes an efficient rule-based paging strategy (RBPS) using a well-known concept of artificial intelligence, namely, rule base. The novelty of the scheme lies in devising "rules" that offer a potential mapping from seemingly disparate input data items (yet having some statistical relations) to an almost exact position of mobile terminals (MTs). Considering the conventional models of call arrival, cell residence, and mobility, we have developed a stochastic model to analyze the performance of the scheme. Interestingly, RBPS requires no additional processing at NITS and involves a nominal overhead at mobile switching centers. Simulation results reveal that RBPS significantly outperforms the blanket paging scheme adopted in Global System for Mobile (GSM) communications. In addition, results are very much encouraging when compared with the popular shortest-distance-first scheme. Finally, RBPS is generic enough to be potentially used in next-generation wireless networks, irrespective of any standards, with only minor adaptations to conform to the respective standards.

  • 425.
    Maknys, Kestutis
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Douhéret, Olivier
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Anand, Srinivasan
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Electrical characterization of InGaAs/InP quantum wells by scanning capacitance microscopy2018In: Microscopy of Semiconducting Materials 2003, CRC Press, 2018, p. 645-648Chapter in book (Refereed)
    Abstract [en]

    In this work, cross-sectional scanning capacitance microscopy (SCM) is used to investigate 5, 10, and 20 nm InGaAs/InP (lattice matched) quantum wells grown by metalorganic vapour phase epitaxy and sandwiched between Si-doped InP barriers. It is demonstrated that SCM is capable of detecting the electrons accumulated in the quantum wells and that the SCM signal shows a systematic trend for the wells of different width. It is also shown that at appropriate tip-sample DC biases depletion regions in the barriers adjacent to the wells are clearly resolved.

  • 426.
    Malm, B. Gunnar
    et al.
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Haralson, E.
    Suvar, E.
    Radamson, Henry H.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Wang, Yong-Bin
    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.
    Base resistance scaling for SiGeC HBTs with a fully nickel-silicided extrinsic base2005In: IEEE Electron Device Letters, ISSN 0741-3106, E-ISSN 1558-0563, Vol. 26, no 4, p. 246-248Article in journal (Refereed)
    Abstract [en]

    A novel SiGeC HBT process with a quasi-self-aligned emitter-base architecture and a fully nickel-silicided extrinsic base region has been developed. A very low total base resistance R-B was achieved along with simultaneous NiSi formation on the polycrystalline emitter and collector regions. Uniform silicide formation was obtained across the wafer, and the resistivity. of the Ni(SiGe:C) silicide layer was 24 mu Omega (.) cm. About 50-100 nm of lateral growth of silicide,. underneath the emitter pedestal was observed. DC and HF results with balanced f(T)/f(MAX) values of 41/42 GHz were demonstrated for 0.5 X 10 mu m(2) transistors.

  • 427.
    Malm, Bengt Gunnar
    et al.
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    von Haartman, Martin
    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.
    Influence of dislocations on low frequency noise in nMOSFETs fabricated on tensile strained virtual substrates2007In: Noise and Fluctuations / [ed] Tacano, M; Yamamoto, Y; Nakao, M, 2007, Vol. 922, p. 133-136Conference paper (Refereed)
    Abstract [en]

    In this work sSi nMOSFETs with 13 run sSi thickness on 27% Ge virtual substrates (VS) are investigated and an increased LF noise level with a characteristic gate bias dependence is found. High off-state leakage of the MOSFETs indicates the presence of misfit dislocations in the channel region. A channel conductance based model is proposed to analyse the noise originating from a highly localized defect in the channel.

  • 428.
    Malm, Gunnar
    et al.
    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.
    Network analyzer measurements and physically based analysis of amplitude and phase distortion in SiGeC HBTs2005In: 2005 International Semiconductor Device Research Symposium, 2005, p. 74-75Conference paper (Refereed)
    Abstract [en]

    We have investigated the linearity of advanced SiGeC bipolar transistors for different bias and input power conditions. The SiGeC HBTs were fabricated in an advanced process, with low base resistance, a minimum emitter area of 10 × 0.4 μm2, and balanced fT/fMAX values of 40-50 GHz. The BVCEO is approximately 2 V. For RF integrated circuits the linearity, i.e. distortion is an important issue. Harmonic and intermodulation distortion in Si and SiGe bipolar transistors has been discussed by several authors from a modelling perspective. However, the experimental studies on high-performance SiGe devices are limited so far. In this work the RF harmonic distortion was characterized by a novel approach using a 2-port network analyzer with a frequency offset option for the receiver port. Both amplitude and phase distortion results could be obtained in a fast and efficient manner. At each port of the network analyzer the power and the phase of the signal (A/B) a reference (R1/R2) are available. When port 2 is tuned to the fundamental frequency the S-parameters are directly obtained and standard 12-term error correction techniques (SOLT/TRL) can be applied. In the case where the port 2 is tuned to another frequency only direct power measurements of A and B are possible and the response at the 2ND and 3RD harmonic frequency has to be adjusted for the attenuation between the DUT and the network analyzer ports using a thru-structure measurement. Figure 1. shows typical output vs. input power characteristics at a DC collector current I C close to peak RF-gain. Due to the relatively low VCE of 1 V saturation will influence both gain compression and linearity. Since the load and source impedance of 50 Ω is the same for the direct power and S-parameter measurements we can compare uncorrected gain and the gain calculated from the corrected S-parameters using |S21| 2. In Figure 2 it observed that the gain difference is 1 - 2 dB. The harmonic distortion vs. IC is shown in Fig. 3 for three different input power levels. Characteristic minima are observed in the 2ND harmonics at 4 mA and the third harmonic at 0.6 mA. Previous studies have indicated that this effect is caused by cancellation between different non-linear, bias dependent effects, such as the collector-base capacitance CBC and transit time τEC. The cancellation occurs due to the phase difference in the non-linear components. To examine this effect we have plotted the phase of the measured output signal at the fundamental and harmonic frequencies, as shown in Fig. 4. The phase of the fundamental shows an expected change at high current due to increased transit time caused by base push-out. The behaviour at the 2ND harmonic shows a drastic phase turn close to 4 mA, which corresponds neatly to the minimum in Fig 3. Since the phase is almost constant at lower IC this suggests that two separate effects dominate the 2ND harmonic at low and high IC respectively. The rapid phase turn is similar to a resonance and thus complete cancellation could occur for a specific current, given that no other non-linear effects were contributing. The minima in the power and the phase turn of the 3RD harmonic are mainly related to the derivative of the 2ND harmonic. The most important non-linear element in the transistor at high IC and VCE close to saturation is CBC, which can be extracted from the S-parameters after standard open-pad de-embedding. In Fig. 5 it is observed that CBC increases strongly for IC larger than 10 mA. As a result the non-linear current generated by CBC will change in both amplitude and phase. Finally, the phase difference between different non-linear effects in the transistor depends on the transit time τEC. The τEC of the SiGeC HBT can be obtained from the phase of S21. Figure 6 shows the change in τEC in for different input power levels. Under large signal conditions the minimum τEC is higher and starts to increase at a lower IC since the transistor is driven into saturation by the large output signal swing. In conclusion, the analysis, using a 2-port network analyzer, of the phase behaviour at harmonic frequencies is useful to find the origin of the distortion in the SiGeC bipolar device structure.

  • 429. Mansson, M.
    et al.
    Claesson, T.
    Finazzi, M.
    Dallera, C.
    Brookes, N. B.
    Tjernberg, Oscar
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Using High Energy Angle Resolved Photoelectron Spectroscopy to Reveal the Charge Density in Solids2008In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 101, no 22Article in journal (Refereed)
    Abstract [en]

    The charge density in solids is a fundamental parameter. Here we demonstrate that the charge density can be determined by the use of angle resolved photoelectron spectroscopy. The method, which involves a Fourier-like transform from momentum space to real space, is demonstrated by utilizing soft x-ray angle resolved photoelectron spectroscopy to sample the complete three-dimensional Brillouin zone of copper. It is also shown that this can be done in an energy resolved way as to extract the charge density contribution from states of a particular energy.

  • 430. March, V.
    et al.
    Teo, Y. M.
    Lim, H. B.
    Eriksson, Peter
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Ayani, Rassul
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Collision detection and resolution in hierarchical peer-to-peer systems2005In: Proceedings - Conference on Local Computer Networks, LCN, 2005, p. 2-9Conference paper (Refereed)
    Abstract [en]

    Structured peer-to-peer systems can be organized hierarchically as two-level overlay networks. The top-level overlay consists of groups of nodes, where each group is identified by a group identifier. In each group, one or more nodes are designated as supernodes and act as gateways to the nodes at the second level. A collision occurs during join operations, when two or more groups with the same group identifier are created at the top-level overlay. Collisions increase the lookup path length and the stabilization overhead, and reduce the scalability of hierarchical peer-to-peer systems. We propose a new scheme to detect and resolve collisions, and we study the impact of the collision problem on the performance of peer-to-peer systems. Our simulation results show the effectiveness of our scheme in reducing collisions and maintaining the size of the top-level overlay close to the ideal size.

  • 431.
    Marcinkevicius, Saulius
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Zhao, Q.X.
    Spin relaxation in charged InAs/GaAs quantum dots2005In: COMPOUND SEMICONDUCTORS 2004, PROCEEDINGS / [ed] Woo, JC; Hasegawa, H; Kwon, YS; Yao, T; Yoo, KH, 2005, Vol. 184, p. 443-446Conference paper (Refereed)
    Abstract [en]

    Photoexcited electron and hole spin relaxation has been studied in modulation doped InAs/GaAs self-assembled quantum dots by means of time resolved photoluminescence. The electron spin relaxation times of 50 to 70 ps have been found for the undoped and p-doped samples, while the hole spins randomise on a much shorter time scale. Electrons preserve their spin orientation during capture and relaxation for excitation into the barriers, however, no preferential spin polarisation has been detected for carrier excitation directly into the dots.

  • 432.
    Marcinkevičius, Saulius
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Siegert, Jörg
    KTH, School of Engineering Sciences (SCI), Physics.
    Carrier capture and relaxation in modulation doped InAs quantum dots2005Conference paper (Refereed)
    Abstract [en]

    Carrier dynamics in n and p-doped and undoped InAs/GaAs quantum dots were studied by time-resolved photoluminescence with selective excitation. Ultrafast carrier relaxation in doped dots is attributed to efficient carrier-carrier scattering.

  • 433.
    Marco Arranz, Carlos Aurello
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    IP Telephony: Peer-to-peer versus SIP2005Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In recent years dramatic technology developments have exploited the development of better transmission media and allowed for broad internet penetration. This in turn has fostered the growth of IP telephony calls, i.e., Voice over IP (VoIP).

    New VoIP products are introduced almost daily, each seeking an opportunity in the market. Some of these products are free - thus putting pressure on other vendors. A good example of a commercial VoIP product is Skype. It is possibly the most important one as it has gained more than 3 millions users in approximately 2 years time. In contrast, Minisip is a non-commercial implementation of SIP developed by students at KTH. These programs are based on different architectures. While Skype is said to be based on a peer-to-peer protocol, Minisip utilized the Session Initiation Protocol (SIP) protocol.

    The aim of this thesis was to evaluate these two VoIP programs not only in terms of development, but also in terms of the quality of service and user perceived voice quality. The study of efficiency, usability, and installation of both are also in the scope of this thesis. The devices used for the evaluation included a HP iPAQ 5550, two PCs running in RedHat Linux 9, and a laptop running Microsoft Windows XP.

  • 434. Marsh, Ian
    et al.
    Severiano, Juan Carlos Martín
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Nunes, Victor
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture (Closed 20120101), Telecommunication Systems Laboratory, TSLab (closed 2012-01-01).
    Maguire, Gerald Q.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    IEEE 802.11b voice quality assessment using crosslayer information.2006Conference paper (Refereed)
    Abstract [en]

    This paper reports on the suitability of IEEE802.11b networks for carrying real-time voice traffic, considering particularly the end terminals. More specifically we looked at such networks in different operating circumstances:an outdoor environment, an office environment,and the influence of competing traffic. Additionally wehave investigated the link protocol in combination with theapplication layer. Based on over 2500 recorded sessions,it can be generally concluded that the 802.11b protocolcan support real-time voice; particularly if the link transmissionrate is immediately lowered after an unsuccessful initial transmission. However, we did find situations where the voice quality deteriorated below commonly accepted values, such as when competing with high-rate TCP traffic,when intervening obstacles blocked the transmission path,and with certain uses of the RTS/CTS mechanism.

  • 435. Martin, M. J.
    et al.
    Benyattou, T.
    Orobtchouk, R.
    Talneau, A.
    Berrier, A.
    Mulot, M.
    Anand, Srinivasan
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Evidence of Bloch wave propagation within photonic crystal waveguides2006In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 82, no 1, p. 9-12Article in journal (Refereed)
    Abstract [en]

    We report in this paper results obtained from characterizations of photonic band gap waveguide, using near field optical microscopy. We will show evidence of a Bloch wave propagating within our W1 photonic crystal waveguides (PCWs) structure, using a 2D Fourier transform approach. The processed image will then be compared to simulations obtained from plane wave method. This comparison exhibits that near-field measurements, using tapered optical fibers as probes, are mainly sensitive to the electric field propagating within the structure.

  • 436.
    Martinelli, Andrés
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Advances in Functional Decomposition: Theory and Applications2006Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Functional decomposition aims at finding efficient representations for Boolean functions. It is used in many applications, including multi-level logic synthesis, formal verification, and testing.

    This dissertation presents novel heuristic algorithms for functional decomposition. These algorithms take advantage of suitable representations of the Boolean functions in order to be efficient.

    The first two algorithms compute simple-disjoint and disjoint-support decompositions. They are based on representing the target function by a Reduced Ordered Binary Decision Diagram (BDD). Unlike other BDD-based algorithms, the presented ones can deal with larger target functions and produce more decompositions without requiring expensive manipulations of the representation, particularly BDD reordering.

    The third algorithm also finds disjoint-support decompositions, but it is based on a technique which integrates circuit graph analysis and BDD-based decomposition. The combination of the two approaches results in an algorithm which is more robust than a purely BDD-based one, and that improves both the quality of the results and the running time.

    The fourth algorithm uses circuit graph analysis to obtain non-disjoint decompositions. We show that the problem of computing non-disjoint decompositions can be reduced to the problem of computing multiple-vertex dominators. We also prove that multiple-vertex dominators can be found in polynomial time. This result is important because there is no known polynomial time algorithm for computing all non-disjoint decompositions of a Boolean function.

    The fifth algorithm provides an efficient means to decompose a function at the circuit graph level, by using information derived from a BDD representation. This is done without the expensive circuit re-synthesis normally associated with BDD-based decomposition approaches.

    Finally we present two publications that resulted from the many detours we have taken along the winding path of our research.

  • 437.
    Martinelli, Andrés
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Dubrova, Elena
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    An efficient structural technique for boolean decomposition2005In: VLSI Circuits and Systems II, Pts 1 and 2 / [ed] Lopez, JF; Fernandez, FV; LopezVillegas, JM; DelaRosa, JM, BELLINGHAM: SPIE-INT SOC OPTICAL ENGINEERING , 2005, Vol. 5837, p. 913-918Conference paper (Refereed)
    Abstract [en]

    Boolean decomposition techniques offer a powerful alternative to traditional algebraic methods when partitioning a circuit graph in the technology independent stage of the circuit design flow. These techniques usually require to transform the circuit from a structural representation to a representation based on Binary Decision Diagrams (BDDs). It is well known that BDDs can grow exponentially in some cases, so the power of Boolean decomposition comes at the expense of an exponential increase in the size of the circuit representation. The following stages in the design flow may suffer severely from the space penalty imposed on each partitioned block. To cope with this space explosion, each block of the partitioned circuit has to be re-synthesized before further processing. The extra re-synthesis, on the other hand, may impose a prohibitive time/space penalty on the design flow. This paper proposes an inexpensive technique to avoid re-synthesizing the BDD blocks obtained after Boolean decomposition. This technique works by structurally partitioning the original circuit representation, according to information provided by the partitioned BDD blocks. After all the blocks have been recovered, the BDDs are not needed and can be discarded. The resulting circuit will be proportional to the original circuit representation, and not to the intermediate BDD representation.

  • 438.
    Martinelli, Andrés
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Dubrova, Elena
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Bound set selection and circuit re-synthesis for area/delay driven decomposition2005In: DESIGN, AUTOMATION AND TEST IN EUROPE CONFERENCE AND EXHIBITION, VOLS 1 AND 2, PROCEEDINGS, 2005, p. 430-431Conference paper (Refereed)
    Abstract [en]

    This paper addresses two problems related to disjoint-support decomposition of Boolean functions. First, we present a heuristic for finding a subset of variables, X, which results in the disjoint-support decomposition f(X, Y) = h(g(X), Y) with a good area/delay trade-off. Second, we present a technique for re-synthesis of the original circuit implementing f (X, Y) into a circuit implementing the decomposed representation h(g(x), Y)Preliminary experimental results indicate that the proposed approach has a significant potential.

  • 439. Martini, Barbara
    et al.
    Baroncelli, Fabio
    Castoldi, Piero
    Muchanga, Américo Francisco
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    The Service Oriented Optical Network (SOON) project2005In: Transparent Optical Networks, 2005, Proceedings of 2005 7th International Conference, NEW YORK: IEEE , 2005, p. 429-432Conference paper (Refereed)
    Abstract [en]

    The Service Oriented Optical Network is a project committed to introduce the concept of service virtualization in optical metro/core networks, by improving the Automatic Switched Transport Network (ASTN) architecture thanks to the introduction of an extra functional layer, namely Service Plane, designed according to the ITU-T Intelligent Network Conceptual Model. An implementation of the Service Plane is presented highlighting the software architecture and the technology details. In particular it is applied to a testbed that implement a VPN topology request from a client application.

  • 440. Martz, J.
    et al.
    Ferrini, R.
    Nuesch, F.
    Zuppiroli, L.
    Wild, B.
    Dunbar, L. A.
    Houdre, R.
    Mulot, M.
    Anand, Srinivasan
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Liquid crystal infiltration of InP-based planar photonic crystals2006In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 99, no 10Article in journal (Refereed)
    Abstract [en]

    A procedure for the infiltration of planar photonic crystals (PhCs) with liquid crystals (LCs) is presented. InP-based PhCs are infiltrated with the nematic LC-K15 in a specially designed high-vacuum chamber. The infiltration technique is validated and systematically characterized by measuring the transmission through the infiltrated PhCs at different temperatures and for different polarizations. The reproducibility and reliability of our procedure are demonstrated and a high filling efficiency is obtained.

  • 441. Martz, J.
    et al.
    Wild, B.
    Ferrini, R.
    Dunbar, L. A.
    Mulot, Mikael
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Anand, Srinivasan
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Houdré, R.
    Zuppiroli, L.
    Tuning the optical properties of planar photonic crystals by liquid crystal infiltration2005In: Proc SPIE Int Soc Opt Eng, 2005, p. 1-14Conference paper (Refereed)
    Abstract [en]

    Recently there has been a growing amount of attention devoted to tuneable photonic crystals (PhCs) where the optical response of PhC structures can be dynamically modified. We will show how infiltrating planar PhCs with a synthetic organic material allows the trimming and tuning of their optical properties. The potential of PhC infiltration will be demonstrated for InP-based planar PhCs consisting of a hexagonal array of air holes (hole diameter = 200 - 400 nm; air filling factor = 0.40-0.50) etched through a planar waveguide in which light emitters (i.e. quantum wells) were embedded to enable optical measurements. The PhC pores were infiltrated with LC-K15 (5CB) nematic liquid crystals (LCs) in a specifically designed vacuum chamber, thereby changing the refractive index contrast between the holes and the semiconductor (trimming). Moreover, the possibility of tuning the optical response of PhCs by an external perturbation (i.e. temperature) was demonstrated. The change of the PhC optical properties due to infiltration and temperature tuning was studied both experimentally and theoretically. Experimental measurements were compared to theoretical calculations in order to obtain information on the in-filling efficiency, the LC refractive index, and the molecule orientation inside the holes. In the first case, optical measurements were performed as a function of temperature, whilst the average LC director configuration was determined by comparing transmission spectra in the transverse electric and magnetic polarization directions.

  • 442. Mathaikutty, Deepak A.
    et al.
    Patel, Hiren D.
    Shukla, Sandeep K.
    Jantsch, Axel
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    SML-Sys: a functional framework with multiple models of computation for modeling heterogeneous system2008In: Design automation for embedded systems, ISSN 0929-5585, E-ISSN 1572-8080, Vol. 12, no 1-2, p. 1-30Article in journal (Refereed)
    Abstract [en]

    System-on-Chip and other complex distributed hardware/software systems contain heterogeneous components. High-level modeling of such systems require frameworks that provide designers with the ability to express concepts of models of computation (MoC)s as modeling constructs. Many system-level modeling frameworks and corresponding modeling notations such as Ptolemy II and SystemC-H facilitate multi-MoC modeling but are based on imperative programming languages (C++, Java, etc). In such frameworks, the computation and communication aspects between the components of models get intertwined thereby hindering its amenability to formal analysis. In this work, we illustrate function-based semantic definitions of MoCs, which are formulated in a functional framework called SML-Sys. We illustrate through a number of examples how to create system models using this functional programming paradigm.

  • 443.
    Mathaikutty, Deepak A.
    et al.
    Virginia Tech, Ctr Embedded Syst Crit Applicat, Blacksburg, VA 24061 USA..
    Patel, Hiren D.
    Virginia Tech, Ctr Embedded Syst Crit Applicat, Blacksburg, VA 24061 USA..
    Shukla, Sandeep K.
    Virginia Tech, Ctr Embedded Syst Crit Applicat, Blacksburg, VA 24061 USA..
    Jantsch, Axel
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    UMoC plus plus: A C plus plus -based Multi-MoC modeling environment2006In: APPLICATIONS OF SPECIFICATION AND DESIGN LANGUAGES FOR SOCS / [ed] Vachoux, A, SPRINGER , 2006, p. 115-130Conference paper (Refereed)
    Abstract [en]

    System-on-chip (SoC) and other complex distributed hardware/software systems contain heterogeneous components that necessitate frameworks capable of expressing heterogeneous models of computation (MoCs) for modeling their functionalities. System-level design languages (SLDLs) that facilitate multi-MoC modeling should have well-defined semantics and should be readily subjected to formal analysis to handle the design complexity. As a result, we follow the multi-MoC paradigm based on timing abstraction and functional parameterizations that have rigorous denotational semantics, which are compliant to functional idioms as shown in functional frameworks such as ForSyDe and SML-Sys. However, functional frameworks are not widely used in the industry due to issues related to efficiency and interoperability with other widely used SLDLs. This imposes a requirement for an imperative language-based implementation of these generic MoCs that offers all the advantages of the underlying formal semantics. In this chapter, we formulate the basis for having generic MoCs in an imperative language and describe the implementation of an untimed modeling framework called UMoC++.

  • 444. Mathaikutty, Deepak Abraham
    et al.
    Patel, Hiren
    Shukla, Sandeep K.
    Jantsch, Axel
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    UMoC++: A C++-Based Multi-MoC Modeling Environment2006In: Advances in Design and Specification Languages for SoCs: Selected Contributions from FDL’05 / [ed] A. Vachoux, Springer Publishing Company, 2006, p. 115-130Conference paper (Refereed)
    Abstract [en]

    System-on-chip (SoC) and other complex distributed hardware/software systemscontain heterogeneous components that necessitate frameworks capable of expressingheterogeneous models of computation (MoCs) for modeling their functionalities.System-level design languages (SLDLs) that facilitate multi-MoCmodeling should have well-defined semantics and should be readily subjectedto formal analysis to handle the design complexity. As a result, we follow themulti-MoC paradigm based on timing abstraction and functional parameterizationsthat have rigorous denotational semantics, which are compliant to functionalidioms as shown in functional frameworks such as ForSyDe and SML-Sys.However, functional frameworks are not widely used in the industry due toissues related to efficiency and interoperability with other widely used SLDLs.This imposes a requirement for an imperative language-based implementationof these generic MoCs that offers all the advantages of the underlying formalsemantics. In this chapter, we formulate the basis for having generic MoCs in animperative language and describe the implementation of an untimed modelingframework called UMoC++.

  • 445. Mathaikutty, Deepak
    et al.
    Patel, Hiren
    Shukla, Sandeep
    Jantsch, Axel
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    EWD: A metamodeling driven customizable multi-MoC system modeling framework2007In: ACM Transactions on Design Automation of Electronic Systems, ISSN 1084-4309, E-ISSN 1557-7309, Vol. 12, no 3, p. 1255470-Article in journal (Refereed)
    Abstract [en]

    We present the EWD design environment and methodology, a modeling and simulation framework suited for complex and heterogeneous embedded systems with varying degrees of expressibility and modeling fidelity. This environment promotes the use of multiple models of computation (MoCs) to support heterogeneity and metamodeling for conformance tests of syntactic and static semantics during the process of modeling. Therefore, EWD is a multiple MoC rnodeling and simulation framework that ensures conformance of the MoC formalisms during model construction using a metamodeling approach. In addition, EWD provides a suite of translation tools that generate executable models for two simulation frameworks to demonstrate its language-independent modeling framework. The EWD methodology uses the Generic Modeling Environment for customization of the MoC-specific modeling syntax into a visual representation. To embed the execution semantics of the MoCs into the models, we have built parsing and translation tools that leverage an XML-based interoperability language. This interoperability language is then translated into executable Standard ML or Haskell models that can also be analyzed by existing simulation frameworks such as SML-Sys or ForSyDe. In summary, EWD is a metamodeling driven multitarget design environment with multi-MoC modeling capability.

  • 446.
    Mattila, Marika
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Secure Communication in Mobile Internet2001Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The number of mobile devices is increasing rapidly. In a couple of years these handheld devices will continuously be connected to the Internet. Also the popularity of business on the Internet rises as the electronic medium provides several advantages compared to the traditional way. These are only some of the factors that are causing growing concern for security in mobile communication.

    Today there are several products for authentication and secure communication over the Internet. However, most algorithms and techniques were designed and optimised for stationary clients such as PCs, which have a high bandwidth network connection and endless power. Handheld devices with less memory, a less powerful CPU, and only narrow bandwidth network connection have more limited possibilities for security than stationary PCs.

    The purpose of this M.Sc Thesis was to examine the suitability of the existing techniques for authentication and secure communication for handheld devices in the mobile Internet.

    Evaluation of different algorithms shows that the Rijndael algorithm and Elliptic Curves techniques are the most suitable ones for mobile devices. The security protocol I recommend today is SSL.

  • 447.
    Mbairi, Felix
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Siebert, Peter
    Mid Sweden University, Sweden.
    Hesselbom, Hjalmar
    Mid Sweden University, Sweden.
    On the problem of using guard traces for high frequency differential lines crosstalk reduction2007In: IEEE transactions on components and packaging technologies (Print), ISSN 1521-3331, E-ISSN 1557-9972, Vol. 30, no 1, p. 67-74Article in journal (Refereed)
    Abstract [en]

    In this paper, the problem of using guard traces for reducing crosstalk between differential transmission line pairs is investigated, both experimentally and by full-wave electromagnetic (EM) simulations. Different cases of differential lines crosstalk are treated with and without guard trace separation between the differential line pairs. Coated microstrip printed circuit board test structures including thru-reflect-line calibration standards are designed and fabricated on a high frequency laminate material, allowing direct measurement of crosstalk between adjacent differential line pairs in the absence and in the presence of guard traces stitched with vias of regular spacing. The test structures are characterized with mixed-mode scattering parameters using a physical layer test system. Different configurations (of differential line pairs) without guard trace, with floating guard traces (which are terminated and nonterminated) and with a solid guard trace separation are investigated using a High Frequency Structure Simulator (a commercial full-wave 3-D EM simulation tool). The experimental data are compared with the simulation results, and some conclusions and guidelines on the effect of guard traces for alleviating crosstalk between differential transmission lines are presented.

  • 448. McDonald, David
    et al.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP. KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT. KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Spano, Paolo
    O’Gorman, James
    Measurement and parameter extraction of semiconductor lasers: experiences of the pan-European action COST 2401998In: Laser Diodes and Applications III, Vol. 3415, p. 152-163Article in journal (Refereed)
  • 449. Medarde, M.
    et al.
    Dallera, C.
    Grioni, M.
    Voigt, J.
    Podlesnyak, A.
    Pomjakushina, E.
    Conder, K.
    Neisius, T.
    Tjernberg, Oscar
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Barilo, S. N.
    Low-temperature spin-state transition in LaCoO3 investigated using resonant x-ray absorption at the CoK edge2006In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 73, no 5Article in journal (Refereed)
    Abstract [en]

    LaCoO3 displays two broad anomalies in the DC magnetic susceptibility chi(DC), occurring, respectively, around 50 K and 500 K. We have investigated the first of them within the 10 K < T < RT temperature range using Co K alpha(1) x-ray absorption spectroscopy (XAS) in the partial fluorescence yield mode. In contrast with previous O K-edge XAS reports, our data show the existence of abrupt changes around 50 K which can be nicely correlated with the anomaly in chi(DC). To our knowledge, this is the first time that a clear, quantitative relationship between the temperature dependence of the magnetic susceptibility and that of the XAS spectra is reported. The intensity changes in the preedge region, which are consistent with a transition from a lower to a higher spin state, have been analyzed using a minimal model including the Co 3d and O 2p hybridization in the initial state. The temperature dependence of the Co magnetic moment obtained from the estimated e(g) and t(2g) occupations could be satisfactorily reproduced. Also, the decrease of the Co 3d and O 2p hybridization by increasing temperature obtained from this simple model compares favorably with the values estimated from thermal evolution of the crystallographic structure.

  • 450. Metwally, N
    et al.
    Wahiddin, M R B
    Bourennane, Mohamed
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Coherent information losses between two-qubit pair interacting with an environment2006In: Optics Communications, ISSN 0030-4018, E-ISSN 1873-0310, Vol. 257, no 1, p. 206-215Article in journal (Refereed)
    Abstract [en]

    We quantify the amount of information exchanged between a system of two qubit pair and the environment. We find that there is a good chance for an Eavesdropper to distill information from the entangled qubits. This chance decreases for less entangled qubits. In particular, we considered two examples: The first is an entangled pure two qubit state and the second an entangled state from two cavities, with a depolarizing channel as an environment. Also the effect of decoherence due to the channel parameter is studied.

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