Endre søk
Begrens søket
1 - 16 of 16
RefereraExporteraLink til resultatlisten
Permanent link
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Treff pr side
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Forfatter A-Ø
  • Forfatter Ø-A
  • Tittel A-Ø
  • Tittel Ø-A
  • Type publikasjon A-Ø
  • Type publikasjon Ø-A
  • Eldste først
  • Nyeste først
  • Skapad (Eldste først)
  • Skapad (Nyeste først)
  • Senast uppdaterad (Eldste først)
  • Senast uppdaterad (Nyeste først)
  • Disputationsdatum (tidligste først)
  • Disputationsdatum (siste først)
  • Standard (Relevans)
  • Forfatter A-Ø
  • Forfatter Ø-A
  • Tittel A-Ø
  • Tittel Ø-A
  • Type publikasjon A-Ø
  • Type publikasjon Ø-A
  • Eldste først
  • Nyeste først
  • Skapad (Eldste først)
  • Skapad (Nyeste først)
  • Senast uppdaterad (Eldste først)
  • Senast uppdaterad (Nyeste først)
  • Disputationsdatum (tidligste først)
  • Disputationsdatum (siste først)
Merk
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 1.
    Alayon Glasunov, Andrés
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Prasad, S.
    Händel, Peter
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Experimental characterization of the propagation channel along a very large virtual array in a reverberation chamber2014Inngår i: Progress in Electromagnetics Research B, ISSN 1937-6472, E-ISSN 1937-6472, nr 59, s. 205-217Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We show that the combined use of radio frequency absorbers and directive antennas can produce significant changes of the radio propagation channel properties along the positions of a virtual array inside a reverberation chamber. A multidimensional characterization of the channel was performed at 40 antenna positions with spacing of 0:233λ at 1 GHz. The average power, the Ricean K-factor, the coherence bandwidth, the r.m.s. delay spread, the mean delay, the beamforming power angle spectrum and array antenna correlation have been studied for different arrangements in the reverberation chamber. The analysis shows that the joint average over time and frequency channel behavior is, as expected, rather homogeneous along the very large array. However, individual realizations of the channel present a pronounced selective behavior in space, time and frequency with parameters varying along the positions of the virtual array suggesting that a heterogeneous behavior of the radio channels can be emulated in reverberation chambers. An important application of the presented study comprises testing of antenna array designs and algorithms in multipath environments. Further development may lead to Over The Air testing of Multiple Input Multiple Output antenna systems of various sizes, i.e., from small to very large arrays.

  • 2.
    Alayon Glazunov, Andres
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Zhang, Jie
    The University of Sheffield.
    On Some Optimal MIMO Antenna Coefficients in Multipath Channels2011Inngår i: Progress in Electromagnetics Research B, ISSN 1937-6472, E-ISSN 1937-6472, Vol. 35, s. 87-109Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper derives some optimum transmit and receive antenna coefficients in wireless multipath channels based on the spherical vector wave multimode expansion of the multiple-input multiple-output (MIMO) channel matrix. The derived antenna coefficients satisfy the following specific optimization criteria: (i) maximum MIMO mean effective link gain (link MEG) based on the multimode channel realizations or (ii) maximum MIMO link MEG based on the multimode correlation matrix or (iii) correlation minimization by diagonalization of the MIMO full-correlation matrix. It is shown that the proposed approach leads to matrix equations belonging to the nearest Kronecker product (NKP) problem family, which in general have no trivial solution. However, we show that exact solutions are provided to the posed NKP problems under the assumption of the Kronecker model for the MIMO full-correlation matrix. The results are illustrated by numerical examples. The proposed approach is a complement to existing antenna pattern analysis methods.

  • 3.
    Alayón Glazunov, Andrés
    et al.
    Division of Electromagnetic Engineering, Royal Institute of Technology (KTH), Stockholm, Sweden.
    Prasad, Sathyaveer
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik. Signal Processing Lab, KTH Royal Institute of Technology, Stockholm, Sweden.
    Händel, Peter
    ACCESS Linnaeus Centre; Signal Processing Lab, KTH Royal Institute of Technology, Stockholm, Sweden.
    Experimental Characterization of the Propagation Channel along aVery Large Virtual Array in a Reverberation Chamber2014Inngår i: Progress in Electromagnetics Research B, ISSN 1937-6472, E-ISSN 1937-6472, Vol. 59, s. 205-217Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We show that the combined use of radio frequency absorbers and directive antennas can produce significant changes of the radio propagation channel properties along the positions of a virtual array inside a reverberation chamber. A multidimensional characterization of the channel was performed at 40 antenna positions with spacing of 0:233λ at 1 GHz. The average power, the Ricean K-factor, the coherence bandwidth, the r.m.s. delay spread, the mean delay, the beamforming power angle spectrum and array antenna correlation have been studied for different arrangements in the reverberation chamber. The analysis shows that the joint average over time and frequency channel behavior is, as expected, rather homogeneous along the very large array. However, individual realizations of the channel present a pronounced selective behavior in space, time and frequency with parameters varying along the positions of the virtual array suggesting that a heterogeneous behavior of the radio channels can be emulated in reverberation chambers. An important application of the presented study comprises testing of antenna array designs and algorithms in multipath environments. Further development may lead to Over The Air testing of Multiple Input Multiple Output antenna systems of various sizes, i.e., from small to very large arrays.

  • 4.
    Daroui, Danesh
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Ekman, Jonas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Performance analysis of parallel non-orthogonal PEEC-based solver for EMC applications2012Inngår i: Progress in Electromagnetics Research B, ISSN 1937-6472, E-ISSN 1937-6472, Vol. 41, s. 77-100Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A parallel implementation of a quasi-static Partial Element Equivalent Circuit (PEEC)-based solver that can handle electromagnetic problems with non-orthogonal structures is presented in this paper. The solver has been written in C++ and employs GMM++ and ScaLAPACK computational libraries to make the solver fast, efficient, and adaptable to current parallel computer systems. The parallel PEEC-based solver has been tested and studied on high performance computing clusters and the correctness of the solver has been verified by doing comparisons between results from orthogonal routines and also another type of electromagnetic solver, namely FEKO. Two non-orthogonal numerical test cases have been analysed in the time and frequency domain. The results are given for solution time and memory consumption while bottlenecks are pointed out and discussed. The benchmarks show a good speedup which gets improved as the problem size is increased. With the capability of the presented solver, the non-orthogonal PEEC formulation is a viable tool for modelling geometrically complex problems.

  • 5.
    Essén, Hanno
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Teoretisk och tillämpad mekanik.
    Sten, J. C. -E
    Nordmark, Arne
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Magnetic energy of surface currents on a torus2013Inngår i: Progress in Electromagnetics Research B, ISSN 1937-6472, E-ISSN 1937-6472, nr 46, s. 357-378Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The magnetic energy and inductance of current distribu-tions on the surface of a torus are considered. Specifically, we investigate the influence of the aspect ratio of the torus, and of the pitch angle for helical current densities, on the energy. We show that, for a fixed surface area of the torus, the energy experiences a minimum for a certain pitch angle. New analytical relationships are presented as well as a review of results scattered in the literature. Results for the ideally conducting torus, as well as for thin rings are given.

  • 6. Fiolhais, Miguel
    et al.
    Essén, Hanno
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Teoretisk och tillämpad mekanik.
    Providencia, Constanta
    Nordmark, Arne
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Biomekanik.
    Magnetic field and current are zero inside ideal conductors2011Inngår i: Progress in Electromagnetics Research B, ISSN 1937-6472, E-ISSN 1937-6472, Vol. 27, s. 187-212Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We prove a theorem on the magnetic energy minimum in a system of perfect, or ideal, conductors. It is analogous to Thomson's theorem on the equilibrium electric field and charge distribution in a system of conductors. We first prove Thomson's theorem using a variational principle. Our new theorem is then derived by similar methods. We find that magnetic energy is minimized when the current distribution is a surface current density with zero interior magnetic field; perfect conductors are perfectly diamagnetic. The results agree with currents in superconductors being confined near the surface. The theorem implies a generalized force that expels current and magnetic field from the interior of a conductor that loses its resistivity. Examples of solutions that obey the theorem are presented.

  • 7.
    Hassan, Emadeldeen
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Wadbro, Eddie
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Berggren, Martin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Patch and ground plane design of microstrip antennas by material distribution topologly optimization2014Inngår i: Progress in Electromagnetics Research B, ISSN 1937-6472, E-ISSN 1937-6472, Vol. 59, s. 89-102Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We use a gradient-based material distribution approach to design conductive parts of microstrip antennas in an efficient way. The approach is based on solutions of the 3D Maxwell's equation computed by the finite-difference time-domain (FDTD) method. Given a set of incoming waves, our objective is to maximize the received energy by determining the conductivity on each Yee-edge in the design domain. The objective function gradient is computed by the adjoint-field method. A microstrip antenna is designed to operate at 1.5 GHz with 0.3 GHz bandwidth. We present two design cases. In the first case, the radiating patch and the finite ground plane are designed in two separate phases, whereas in the second case, the radiating patch and the ground plane are simultaneously designed. We use more than 58,000 design variables and the algorithm converges in less than 150 iterations. The optimized designs have impedance bandwidths of 13% and 36% for the first and second design case, respectively.

  • 8.
    Li, Bing
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Månsson, Daniel
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Yang, Guang
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    An Efficient Method for Solving Frequency Responses of Power-Line Networks2015Inngår i: Progress in Electromagnetics Research B, ISSN 1937-6472, E-ISSN 1937-6472, Vol. 62, nr 1, s. 303-317Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents a novel approach for solving the frequency responses of a powerline network, which is a two-parallel-conductor system with multiple junctions and branches. By correcting the reflection coefficient and transmission coefficient of each junction, a complex network can be decomposed into several, single-junction, units. Based on the Baum-Liu-Tesche (BLT) equation, we preliminarily propose the calculation method of frequency responses for single-junction network. In accordance with the direction of power transfer, we calculate the frequency responses of loads connected to each junction sequentially, from the perspective of the network structure. This approach greatly simplifies the computational complexity of the network frequency responses. To verify the proposed algorithm, networks with various numbers of junctions and branches are investigated, and the results are compared with a commercial electromagnetic simulator based on the topology. The analytical results agree well with the simulated ones.

  • 9.
    Marcusson, Birger
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Lundin, Urban
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Harmonically Time Varying, Traveling Electromagnetic Fields along a Laminate Approximated by a Homogeneous, Anisotropic Block with Infinite Length2017Inngår i: Progress in Electromagnetics Research B, ISSN 1937-6472, E-ISSN 1937-6472Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Analytical expressions that include arbitrarily directed fields on all laminate boundaries can be used for calculation of the fields inside the laminate when the boundary fields are known from, e.g., measurements. A linear laminate block could be used in non-destructive testing for comparisons between different laminates. This article contains derivation of Fourier series of harmonically time varying, traveling electromagnetic fields in homogeneous, anisotropic approximations of laminates. The component of the magnetic field strength in the stacking direction is used as a source term in two-dimensional Poisson equations for the magnetic field strength in other directions. This approximation is here used in three dimensions under the precondition that the conductivity is much smaller in the laminate stacking direction than in the other directions. Sine interpolation and different choices of types of boundary conditions are discussed. Different alternative subdivisions of the Poisson boundary value problems are treated. Shorted derivations of simple analytical expressions are given for both traveling and standing waves in two dimensions. Results from Fourier series in the three-dimensional case are compared with results from finite element calculations.

  • 10.
    Marcusson, Birger
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Lundin, Urban
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Harmonically Time Varying, Traveling Electromagnetic Fields along a Plate and a Laminate with a Rectangular Cross Section, Isotropic Materials and Infinite Length2017Inngår i: Progress in Electromagnetics Research B, ISSN 1937-6472, E-ISSN 1937-6472, Vol. 77, s. 117-136Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This article contains derivation of propagation factors and Fourier series for harmonically time varying, traveling electromagnetic fields in a plate and a laminate with rectangular cross sections, isotropic materials and infinite length. Different and quite general fields are taken into account on all boundaries. Choices of boundary conditions and continuity conditions are discussed. Certain combinations of types of boundary conditions make the derivation possible for a laminate. Comparisons are made between results of Fourier series and finite element calculations.

  • 11.
    Månsson, Daniel
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    On the Optimization of Halbach Arrays as Energy Storage Media2015Inngår i: Progress in Electromagnetics Research B, ISSN 1937-6472, E-ISSN 1937-6472, Vol. 62, nr 1, s. 277-288Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the paper presented here the optimization of Halbach arrays as storage media for mechanical potential energy is investigated with numerical simulations using FEMM and analytical calculations using the Maxwell stress tensor. Two opposing Halbach arrays form a "magnetic spring" and mechanical potential energy is stored when this structure is compressed. It is here seen that the wavelength of the magnetization in the material and the dimensions greatly influence the stored energy density. A clear region of maximum is identified which leads to important conclusions on how the material should be employed. The suggested approach for storing energy have advantages and approximately 250 kJ/m3 can be reached. The main drawback is the large prize of rare earth metals such as Neodymium.

  • 12.
    Månsson, Daniel
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    On the Suitability of Using Halbach Arrays as Potential Energy Storage Media2014Inngår i: Progress in Electromagnetics Research B, ISSN 1937-6472, E-ISSN 1937-6472, Vol. 58, s. 151-166Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the work presented here, the suitability of an unusual energy storage medium is investigated. The energy storage system is based on the forceful compression of two magnetic Halbach arrays. The mass and volume energy density is obtained and compared to existing common energy storage systems. The charge and discharge times and depths are also discussed. In addition, limits and considerations, which are needed for practical implementation, e.g., risk of demagnetization, internal mechanical stresses, heating of the magnetic structure and financial efficiency are investigated.

  • 13.
    Nordebo, Sven
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för fysik och elektroteknik (IFE).
    Gustafsson, Alexander
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för fysik och elektroteknik (IFE).
    A Quasi-Static Electromagnetic Analysis for Experiments with Strong Permanent Magnets2014Inngår i: Progress in Electromagnetics Research B, ISSN 1937-6472, E-ISSN 1937-6472, Vol. 61, s. 1-16Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An electromagnetic analysis is presented for experiments with strong permanent disc magnets. The analysis is based on the well known experiment that demonstrates the effect of circulating eddy currents by dropping a strong magnet through a vertically placed metal cylinder and observing how the magnet is slowly falling through the cylinder with a constant velocity. This experiment is quite spectacular with a super strong neodymium magnet and a thick metal cylinder made of copper or aluminum. A rigorous theory for this experiment is provided based on the quasi-static approximation of the Maxwell equations, an infinitely long cylinder (no edge effects) and a homogeneous magnetization of the disc magnet. The results are useful for teachers and students in electromagnetics who wish to obtain a deeper insight into the analysis and experiments regarding this phenomenon, or with industrial applications such as the grading and calibration of strong permanent magnets or with measurements of the conductivity of various metals, etc.. Several experiments and numerical computations are included to validate and to illustrate the theory.

  • 14.
    Nordebo, Sven
    et al.
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Matematiska och systemtekniska institutionen.
    Gustafsson, M
    A priori modeling for gradient based inverse scattering algorithms2009Inngår i: Progress in Electromagnetics Research B, ISSN 1937-6472, E-ISSN 1937-6472, Vol. 16, s. 407-432Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents a Fisher information based Bayesian approach to analysis and design of the regularization and preconditioning parameters used with gradient based inverse scattering algorithms. In particular, a one-dimensional inverse problem is considered where the permittivity and conductivity profiles are unknown and the input data consist of the scattered field over a certain bandwidth. A priori parameter modeling is considered with linear, exponential and arctangential parameter scalings and robust preconditioners are obtained by choosing the related scaling parameters based on a Fisher information analysis of the known background. The Bayesian approach and a principal parameter (singular value) analysis of the stochastic Cramer-Rao bound provide a natural interpretation of the regularization that is necessary to achieve stable inversion, as well as an indicator to predict the feasibility of achieving successful reconstruction in a given problem set-up. In particular, the Tikhonov regularization scheme is put into a Bayesian estimation framework. A time-domain least-squares inversion algorithm is employed which is based on a quasi-Newton algorithm together with an FDTD-electromagnetic solver. Numerical examples are included to illustrate and verify the analysis.

  • 15.
    Shestopalov, Yury
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Matematik.
    Kuzmina, Ekaterina
    Russian Technological University MIREA, Moscow, Russia.
    On a rigorous proof of the existence of complex waves in a dielectric waveguide of circular cross section2018Inngår i: Progress in Electromagnetics Research B, ISSN 1937-6472, E-ISSN 1937-6472, Vol. 82, s. 137-164Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Existence of symmetric complex waves in a dielectric rod (DR) - a dielectric waveguide of circular cross section - is proved by analyzing functional properties of the dispersion equations (DEs) using the theory of functions of several complex variables and validating the existence of complex roots of DE. A closed-form iteration procedure for calculating the roots in the complex domain supplied with efficient choice of initial approximation is proposed. Numerical modeling is performed with the help of a parameter-differentiation method applied to the analytical and numerical solution of DEs.

  • 16.
    Shestopalov, Yury V.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Matematik.
    Resonant states in waveguide transmission problems2015Inngår i: Progress in Electromagnetics Research B, ISSN 1937-6472, E-ISSN 1937-6472, Vol. 64, nr 1, s. 119-143Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We prove the existence of complex eigenfrequencies of open waveguide resonators in the form of parallel-plate waveguides and waveguides of rectangular crosssection containing layered dielectric inclusions. It is shown that complex eigenfrequencies are finite-multiplicity poles of the analytical continuation of the operator of the initial diffraction problem and its Green's function to a multi-sheet Riemann surface, and also of the transmission coefficient extended to the complex plane of some of the problem parameters. The eigenfrequencies are associated with resonant states (RSs) and eigenvalues of distinct families of Sturm-Liouville problems on the line; they form countable sets of points in the complex plane with the only accumulation point at infinity and depend continuously on the problem parameters. The set of complex eigenfrequencies is similar in its structure to the set of eigenvalues of a Laplacian in a rectangle. The presence of a resonance domain in the form of a parallel-plane layered dielectric insert removes the continuous frequency spectrum and gives rise to a discrete set of points shifted to (upper half of) the complex plane.

1 - 16 of 16
RefereraExporteraLink til resultatlisten
Permanent link
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf