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  • 1. Ao, X. Y.
    et al.
    He, Sailing
    KTH, Superseded Departments, Electromagnetic Theory.
    Subwavelength focusing and imaging by a multimode optical waveguide2004In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 29, no 24, p. 2864-2866Article in journal (Refereed)
  • 2.
    Ao, Xianyu
    et al.
    KTH.
    He, Sailing
    KTH, Superseded Departments, Electromagnetic Theory.
    Two-stage design method for realization of photonic bandgap structures with desired symmetries by interference lithography2004In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 12, no 6, p. 978-983Article in journal (Refereed)
    Abstract [en]

    Interference lithography for the fabrication of photonic crystals is considered. A two-stage design method for realization of photonic bandgap structures with desired symmetries is developed. An optimal photonic crystal with a large bandgap is searched by adjusting some parameters while keeping some basic symmetry of the unit cell unchanged. A nonlinear programming method is then used to find the optimal electric field vectors of the laser beams and realize the desired interference pattern. The present method is useful for a rational and systematical design of new photonic bandgap structures.

  • 3.
    Cao, Jiasu
    KTH, Superseded Departments, Electromagnetic Theory.
    Applications of 3D time domain wave splittings to direct and inverse scattering1998Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    The three-dimensional direct and inverse scattering problems in the time-domain are considered in the present thesis. The direct problem is to find an explicit or numerical solution of the transient reflection for given physical parameters. The inverse problem is to reconstruct the physical parameters in the scattering region, using the reflection data generated by a known incident field. The method used is based on the concept of wave-splitting. To make the thesis more instructive, wave-splitting and the Green function approach are fimt described for the the plane wave case. For stratified half-space with a point source, a spatial Han kel transform is used to obtain a one-dimensional wave equation. The explicit expression for the reflection kemel in the Hankel-transformed space for an expo nential density profile is obtained. Closed-form solution of the transient reflected pressure in physical space is obtained through an inverse Hankel transform. The time domain Green func:ion approach is used to solve the inverse probelm. For a 3D inhomogeneous ha&space in a Cartesian coordinate system, wave-splitting to the three-dimensional wave equation is used. By introducing a lotal continuation and a wave-splitting approach, one can propagate the transient wave field and its normal derivative to the next layer, so that parameter reconstruction can be achieved in a layer-stripping manner. From the up and down-going wave conditions, one can obtain the exact absorbing boundary conditions. Wave-splitting and corresponding absorbing boundary conditions for 3D scattering problems in spherical coordinate system are also discussed in this thesis.

  • 4. Chen, Long
    et al.
    He, Sailing
    KTH, Superseded Departments, Electromagnetic Theory.
    Shen, Linfang
    Finite-size effects of a left-handed material slab on the image quality2004In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 92, no 10Article in journal (Refereed)
    Abstract [en]

    The characteristics of an imaging system formed by a left-handed material (LHM) slab of finite length are studied, and the influence of the finite length of the slab on the image quality is analyzed. Unusual phenomena such as surface bright spots and negative energy stream at the image side are observed and explained as the cavity effects of surface plasmons excited by the evanescent components of the incident field. For a thin LHM slab, the cavity effects are found rather sensitive to the length of the slab; the bright spots on the bottom surface of the slab may stretch to the image plane and degrade the image quality.

  • 5. Cheng, C.
    et al.
    He, Sailing
    KTH, Superseded Departments, Electromagnetic Theory.
    An optimal design for reducing the black center for a copper-vapor laser by using a genetic algorithm2000In: Microwave and optical technology letters (Print), ISSN 0895-2477, E-ISSN 1098-2760, Vol. 25, no 2, p. 113-119Article in journal (Refereed)
  • 6. Cheng, C.
    et al.
    He, Sailing
    KTH, Superseded Departments, Electromagnetic Theory.
    Optimal design for a copper vapor laser with a maximum output by using a genetic algorithm2001In: Optical and quantum electronics, ISSN 0306-8919, E-ISSN 1572-817X, Vol. 33, no 1, p. 83-98Article in journal (Refereed)
  • 7. Dai, D. X.
    et al.
    He, Sailing
    KTH, Superseded Departments, Electromagnetic Theory.
    Analysis of multimode effects in the free-propagation region of a silicon-on-insulator-based arrayed-waveguide grating demultiplexer2003In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 42, no 24, p. 4860-4866Article in journal (Refereed)
  • 8. Dai, D. X.
    et al.
    Liu, S. Z.
    He, Sailing
    KTH, Superseded Departments, Electromagnetic Theory.
    A flattened AWG demultiplexer with low chromatic dispersion2003In: Fiber and integrated optics (Print), ISSN 0146-8030, E-ISSN 1096-4681, Vol. 22, no 3, p. 141-149Article in journal (Refereed)
  • 9. Dai, D. X.
    et al.
    Liu, S. Z.
    He, Sailing
    KTH, Superseded Departments, Electromagnetic Theory.
    Zhou, Q. C.
    Optimal design of an MMI coupler for broadening the spectral response of an AWG demultiplexer2002In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 20, no 11, p. 1957-1961Article in journal (Refereed)
  • 10. Dai, D. X.
    et al.
    Mei, W. Q.
    He, Sailing
    KTH, Superseded Departments, Electromagnetic Theory.
    Using a tapered MMI to flatten the passband of an AWG2003In: Optics Communications, ISSN 0030-4018, E-ISSN 1873-0310, Vol. 219, no 01-6, p. 233-239Article in journal (Refereed)
  • 11.
    Dai, Daoxin
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP. KTH, Superseded Departments, Electromagnetic Theory.
    He, Sailing
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP. KTH, Superseded Departments, Electromagnetic Theory.
    Accurate two-dimensional model of an arrayed-waveguide grating demultiplexer and optimal design based on the reciprocity theory2004In: Journal of the Optical Society of America A: Optics and Image Science, and Vision, ISSN 1084-7529, Vol. 21, no 12, p. 2392-2398Article in journal (Refereed)
    Abstract [en]

    An accurate two-dimensional (2D) model is introduced for the simulation of an arrayed-waveguide grating (AWG) demultiplexer by integrating the field distribution along the vertical direction. The equivalent 2D model has almost the same accuracy as the original three-dimensional model and is more accurate for the AWG considered here than the conventional 2D model based on the effective-index method. To further improve the computational efficiency, the reciprocity theory is applied to the optimal design of a flat-top AWG demultiplexer with a special input structure.

  • 12.
    Dai, Daoxin
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    He, Sailing
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP. KTH, Superseded Departments, Electromagnetic Theory.
    Analysis of the birefringence of a silicon-on-insulator rib waveguide2004In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 43, no 5, p. 1156-1161Article in journal (Refereed)
    Abstract [en]

    A detailed analysis of the polarization characteristics (birefringence) of a silicon-on-insulator (SOI) rib waveguide is given. The fundamental TE- and TM-polarized modes of the SOI rib waveguide are calculated by a semivectorial finite-difference method. The rib width and the slab height of the SOI rib waveguide are normalized with respect to the total height of the silicon layer. A general relation between the two normalized parameters for a nonbirefringent SOI rib waveguide is obtained. According to this relation a nonbirefringent SOI rib waveguide can easily be designed. The fabrication tolerance for a nonbirefringent SOI rib waveguide is also analyzed, revealing that the tolerance can be increased by use of a larger total height of the silicon layer.

  • 13. Frohlich, J.
    et al.
    Gustafson, S.
    Jonsson, B. Lars G.
    KTH, Superseded Departments, Electromagnetic Theory.
    Sigal, I. M.
    Solitary wave dynamics in an external potential2004In: Communications in Mathematical Physics, ISSN 0010-3616, E-ISSN 1432-0916, Vol. 250, no 3, p. 613-642Article in journal (Refereed)
    Abstract [en]

    We study the behavior of solitary-wave solutions of some generalized nonlinear Schrodinger equations with an external potential. The equations have the feature that in the absence of the external potential, they have solutions describing inertial motions of stable solitary waves. We consider solutions of the equations with a non-vanishing external potential corresponding to initial conditions close to one of these solitary wave solutions and show that, over a large interval of time, they describe a solitary wave whose center of mass motion is a solution of Newton's equations of motion for a point particle in the given external potential, up to small corrections corresponding to radiation damping.

  • 14. Fu, J.
    et al.
    He, Sailing
    KTH, Superseded Departments, Electromagnetic Theory.
    Xiao, S. S.
    Analysis of channel-dropping tunnelling processes in photonic crystals with multiple vertical multi-mode cavities2000In: Journal of Physics A: Mathematical and General, ISSN 0305-4470, E-ISSN 1361-6447, Vol. 33, no 43, p. 7761-7771Article in journal (Refereed)
  • 15. Fu, J.
    et al.
    He, Sailing
    KTH, Superseded Departments, Electromagnetic Theory.
    Xiao, S. S.
    Qiu, M.
    He, J. J.
    Theoretical analysis of a vertical channel dropping tunnelling process in a photonic crystal for wavelength division demultiplexing2001In: Chinese Physics Letters, ISSN 0256-307X, E-ISSN 1741-3540, Vol. 18, no 12, p. 1613-1616Article in journal (Refereed)
  • 16. Gustafsson, M.
    et al.
    He, Sailing
    KTH, Superseded Departments, Electromagnetic Theory.
    An optimization approach to multi-dimensional time domain acoustic inverse problems2000In: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 108, no 4, p. 1548-1556Article in journal (Refereed)
  • 17. Gustafsson, M.
    et al.
    He, Sailing
    KTH, Superseded Departments, Electromagnetic Theory.
    An optimization approach to two-dimensional time domain electromagnetic inverse problems2000In: Radio Science, ISSN 0048-6604, E-ISSN 1944-799X, Vol. 35, no 2, p. 525-536Article in journal (Refereed)
  • 18. Gustafsson, M.
    et al.
    Jonsson, B. Lars G.
    KTH, Superseded Departments, Electromagnetic Theory.
    Iterative time reversal retrofocusing of Electromagnetic fields2004Conference paper (Refereed)
  • 19. Gustafsson, M.
    et al.
    Jonsson, B. Lars G.
    KTH, Superseded Departments, Electromagnetic Theory.
    Time Reversal Retrofocusing and Inverse Scattering of Acoustic Wave Fields2003Conference paper (Refereed)
  • 20. Gustafsson, M.
    et al.
    Jonsson, B. Lars G.
    KTH, Superseded Departments, Electromagnetic Theory.
    Time Reversal Retrofocusing and Inverse Scattering of Electromagnetic Wave Fields2003Conference paper (Refereed)
  • 21.
    He, Sailing
    et al.
    KTH, Superseded Departments, Electromagnetic Theory.
    Ao, X. Y.
    Romanov, V.
    General properties of N x M self-images in a strongly confined rectangular waveguide2003In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 42, no 24, p. 4855-4859Article in journal (Refereed)
  • 22.
    He, Sailing
    et al.
    KTH, Superseded Departments, Electromagnetic Theory.
    Norgren, M.
    Magnetostatic image current and its application to an analytic identification of a current dipole inside a conducting sphere2000In: IEEE Transactions on Biomedical Engineering, ISSN 0018-9294, E-ISSN 1558-2531, Vol. 47, no 2, p. 183-191Article in journal (Refereed)
  • 23.
    He, Sailing
    et al.
    KTH, Superseded Departments, Electromagnetic Theory.
    Popov, M.
    Qiu, M.
    Liao, Z. G.
    Simovski, C.
    Explicit formulas for obtaining the radiation characteristics of an antenna based on a three-dimensional metallic photonic bandgap structure2001In: Microwave and optical technology letters (Print), ISSN 0895-2477, E-ISSN 1098-2760, Vol. 29, no 6, p. 376-381Article in journal (Refereed)
  • 24.
    He, Sailing
    et al.
    KTH, Superseded Departments, Electromagnetic Theory.
    Popov, M.
    Qiu, M.
    Simovski, C.
    An explicit method for the analysis of guided waves in a line-defect channel in a photonic crystal2000In: Microwave and optical technology letters (Print), ISSN 0895-2477, E-ISSN 1098-2760, Vol. 25, no 4, p. 236-240Article in journal (Refereed)
  • 25.
    He, Sailing
    et al.
    KTH, Superseded Departments, Electromagnetic Theory.
    Popov, M.
    Qiu, M.
    Simovski, C.
    The influence of the dielectric-air interface on the radiation pattern of an antenna in a metallic photonic bandgap structure in a dielectric host medium2000In: Microwave and optical technology letters (Print), ISSN 0895-2477, E-ISSN 1098-2760, Vol. 26, no 6, p. 367-371Article in journal (Refereed)
  • 26.
    He, Sailing
    et al.
    KTH, Superseded Departments, Electromagnetic Theory.
    Popov, M.
    Romanov, V.
    Explicit full identification of a transient dipole source in the atmosphere from measurement of the electromagnetic fields at several points at ground level2000In: Radio Science, ISSN 0048-6604, E-ISSN 1944-799X, Vol. 35, no 1, p. 107-117Article in journal (Refereed)
  • 27.
    He, Sailing
    et al.
    KTH, Superseded Departments, Electromagnetic Theory.
    Qiu, M.
    Simovski, C. R.
    An averaged-field approach for obtaining the band structure of a dielectric photonic crystal2000In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 12, no 2, p. 99-112Article in journal (Refereed)
  • 28.
    He, Sailing
    et al.
    KTH, Superseded Departments, Electromagnetic Theory.
    Simovski, C. R.
    Popov, M.
    An explicit and efficient method for obtaining the radiation characteristics of wire antennas in metallic photonic bandgap structures2000In: Microwave and optical technology letters (Print), ISSN 0895-2477, E-ISSN 1098-2760, Vol. 26, no 2, p. 67-73Article in journal (Refereed)
  • 29.
    He, Sailing
    et al.
    KTH, Superseded Departments, Electromagnetic Theory.
    Xiao, S. S.
    Shen, L. F.
    He, J. P.
    Fu, J.
    A new finite-difference time-domain method for photonic crystals consisting of nearly-free-electron metals2001In: Journal of Physics A: Mathematical and General, ISSN 0305-4470, E-ISSN 1361-6447, Vol. 34, no 45, p. 9713-9721Article in journal (Refereed)
  • 30.
    He, Sailing
    et al.
    KTH, Superseded Departments, Electromagnetic Theory.
    Xu, J.
    Romanov, V. G.
    A simple analytical method for calculating the leakage loss of a buried rectangular waveguide2004In: Journal of Optics. A, Pure and applied optics, ISSN 1464-4258, E-ISSN 1741-3567, Vol. 6, no 1, p. 57-62Article in journal (Refereed)
    Abstract [en]

    A simple and efficient analytical method is presented for studying leaky modes in a buried rectangular waveguide on a high-refractive-index substrate. The cross-sectional profile of the refractive index for the buried rectangular waveguide is decomposed into three parts. The two main parts correspond to two independent multilayered slab waveguide structures and the remaining part is treated as a small perturbation term. The contributions from all three parts to the leakage loss are given analytically. Numerical results are presented and compared with those calculated with the semi-vectorial finite difference method. Fast speed, satisfactory accuracy and simplicity are the main advantages of the present method.

  • 31.
    He, Sailing
    et al.
    KTH, Superseded Departments, Electromagnetic Theory.
    Zhang, H.
    Romanov, V. G.
    Explicit identification of multiple small breast cancers in an optical mammographic imaging2002In: Inverse Problems, ISSN 0266-5611, E-ISSN 1361-6420, Vol. 18, no 6, p. 1555-1567Article in journal (Refereed)
  • 32.
    Hellberg, Rasmus
    KTH, Superseded Departments, Electromagnetic Theory.
    A time-domain method for the design of non-reflecting media: an inverse problem for dispersive and dissipative plane-stratified media by the wave-splitting and green functions technique1997Doctoral thesis, monograph (Other scientific)
  • 33.
    Holter, Henrik
    KTH, Superseded Departments, Electromagnetic Theory.
    Analysis and design of broadband phased array antennas2000Doctoral thesis, comprehensive summary (Other scientific)
  • 34. Ichein, C.
    et al.
    Popov, M.
    Vainikainen, P.
    He, Sailing
    KTH, Superseded Departments, Electromagnetic Theory.
    Optimal reduction of the influence of RF feed cables in small antenna measurements2000In: Microwave and optical technology letters (Print), ISSN 0895-2477, E-ISSN 1098-2760, Vol. 25, no 3, p. 194-196Article in journal (Refereed)
  • 35.
    Jonsson, B. Lars G.
    et al.
    KTH, Superseded Departments, Electromagnetic Theory.
    de Hoop, M. V.
    Wave field decomposition in anisotropic fluids: A spectral theory approach2001In: Acta Applicandae Mathematicae - An International Survey Journal on Applying Mathematics and Mathematical Applications, ISSN 0167-8019, E-ISSN 1572-9036, Vol. 67, no 2, p. 117-171Article in journal (Refereed)
    Abstract [en]

    An extension of directional wave field decomposition in acoustics from heterogenous isotropic media to generic heterogenous anisotropic media is established. We make a connection between the Dirichlet-to-Neumann map for a level plane, the solution to an algebraic Riccati operator equation, and a projector defined via a Dunford-Taylor type integral over the resolvent of a nonnormal, noncompact matrix operator with continuous spectrum. In the course of the analysis, the spectrum of the Laplace transformed acoustic system's matrix is analyzed and shown to separate into two nontrivial parts. The existence of a projector is established and using a generalized eigenvector procedure, we find the solution to the associated algebraic Riccati operator equation. The solution generates the decomposition of the wave field and is expressed in terms of the elements of a Dunford-Taylor type integral over the resolvent.

  • 36.
    Jonsson, B. Lars G.
    et al.
    KTH, Superseded Departments, Electromagnetic Theory.
    Dejak, S.
    Sigal, I. M.
    On long time dynamics for KdV solitons2003Conference paper (Refereed)
  • 37.
    Jonsson, B. Lars G.
    et al.
    KTH, Superseded Departments, Electromagnetic Theory.
    Fröhlich, J.
    Gustafson, S.
    Sigal, I. M.
    On dynamics of a NLS-soliton in an external potential2003Conference paper (Refereed)
  • 38.
    Jonsson, B. Lars G.
    et al.
    KTH, Superseded Departments, Electromagnetic Theory.
    Gustafsson, M.
    Weston, V. H.
    de Hoop, M. V.
    Retrofocusing for Acoustic and Electromagnetic fields by Iterated Time reversal2003Conference paper (Refereed)
  • 39.
    Jonsson, B. Lars G.
    et al.
    KTH, Superseded Departments, Electromagnetic Theory.
    Gustafsson, M.
    Weston, V. H.
    de Hoop, M. V.
    Retrofocusing of acoustic wave fields by iterated time reversal2004In: SIAM Journal on Applied Mathematics, ISSN 0036-1399, E-ISSN 1095-712X, Vol. 64, no 6, p. 1954-1986Article in journal (Refereed)
    Abstract [en]

    In the present paper an iterative time-reversal algorithm that retrofocuses an acoustic wave field to its controllable part is established. For a fixed temporal support, i.e., transducer excitation time, the algorithm generates an optimal retrofocusing in the least-squares sense. Thus the iterative time-reversal algorithm reduces the temporal support of the excitation from the requirement of negligible remaining energy to the requirement of controllability. The time-reversal retrofocusing is analyzed from a boundary-control perspective where time reversal is used to steer the acoustic wave field towards a desired state. The wave field is controlled by transducers located at subsets of the boundary, i.e., the controllable part of the boundary. The time-reversal cavity and time-reversal mirror cases are analyzed. In the cavity case, the transducers generate a locally plane wave in the fundamental mode through a set of ducts. Numerical examples are given to illustrate the convergence of the iterative time-reversal algorithm. In the mirror case, a homogeneous half space is considered. For this case the analytic expression for the retrofocused wave field is given for finite temporal support. It is shown that the mirror case does not have the same degree of steering as the cavity case. It is also shown that the pressure can be perfectly retrofocused for infinite temporal support. Two examples are given that indicate that the influence of the evanescent part of the wave field is small.

  • 40.
    Jonsson, B. Lars G.
    et al.
    KTH, Superseded Departments, Electromagnetic Theory.
    Sigal, I. M
    Gustafson, S.
    Fröhlich, Jurg
    On dynamics of a soliton in an external potential2003Conference paper (Refereed)
  • 41. Josefsson, L
    et al.
    Persson, Patrik
    KTH, Superseded Departments, Electromagnetic Theory.
    Conformal array synthesis including mutual coupling1999In: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 35, no 8, p. 625-627Article in journal (Refereed)
    Abstract [en]

    A pattern synthesis technique for a conformal array antenna on a cylinder is presented using the method of alternate projections. Both the sidelobe region and the shape of the main beam are controlled. The method includes the effect of the mutual coupling in the synthesis. It is shown that if mutual coupling is neglected, then poor results are obtained, especially in the shaped beam region.

  • 42.
    Kamaly, Amir
    KTH, Superseded Departments, Electromagnetic Theory.
    Type-inequality problems in fourier analysis1998Doctoral thesis, comprehensive summary (Other scientific)
  • 43. Liu, L.
    et al.
    Shi, Z. M.
    He, Sailing
    KTH, Superseded Departments, Electromagnetic Theory.
    Analysis of the polarization-dependent diffraction from a metallic grating by use of a three-dimensional combined vectorial method2004In: Journal of the Optical Society of America a-Optics Image Science and Vision, ISSN 1084-7529, Vol. 21, no 8, p. 1545-1552Article in journal (Refereed)
  • 44.
    Liu, LIu
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    He, Sailing
    KTH, Superseded Departments, Electromagnetic Theory.
    Near-field optical storage system using a solid immersion lens with a left-handed material slab2004In: Optical express, ISSN 1094-4087, Vol. 12, p. 4835-4840Article in journal (Refereed)
    Abstract [en]

    A new near-field optical storage system utilizing a left-handed material (LHM) is introduced by attaching an LHM slab to the lower surface of a conventional solid immersion lens (SIL). The performance of the present storage system is compared with a conventional SIL system through numerical simulation. The LHM slab in the present storage system can image very well the focused spot at the lower surface of the SIL to the surface of a disc. It allows a large air-gap for the mechanical convenience while keeping a large signal contrast and a high storage density. The tolerance of the air-gap is also improved.

  • 45. Lu, J.
    et al.
    He, Sailing
    KTH, Superseded Departments, Electromagnetic Theory.
    Numerical study of a Gaussian beam propagating in media with negative permittivity and permeability by using a bidirectional beam propagation method2003In: Microwave and optical technology letters (Print), ISSN 0895-2477, E-ISSN 1098-2760, Vol. 37, no 4, p. 292-296Article in journal (Refereed)
  • 46. Lu, J.
    et al.
    He, Sailing
    KTH, Superseded Departments, Electromagnetic Theory.
    Romanov, V. G.
    Study of the leakage loss in a silica-on-silicon slab waveguide2003In: Fiber and integrated optics (Print), ISSN 0146-8030, E-ISSN 1096-4681, Vol. 22, no 4, p. 249-261Article in journal (Refereed)
  • 47.
    Norgren, Martin
    et al.
    KTH, Superseded Departments, Electrical Systems.
    He, Sailing
    KTH, Superseded Departments, Electromagnetic Theory.
    Exact and explicit solution to a class of degaussing problems2000In: IEEE transactions on magnetics, ISSN 0018-9464, E-ISSN 1941-0069, Vol. 36, no 1, p. 308-312Article in journal (Refereed)
    Abstract [en]

    An exact and explicit solution to a class of degaussing problems is given. The solution is shown to be unique. The stability of the solution is also analyzed.

  • 48.
    Persson, Patrik
    KTH, Superseded Departments, Electromagnetic Theory.
    Analysis and Design of Conformal Array Antennas2002Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Today there is a great need for communication between people and even between things, using systems onboard e.g. aircraft, cars, ships and satellites. As a consequence, these communications needs require antennas mounted on or integrated in the surfaces of different vehicles or platforms, i.e. conformal antennas. In order to ensure proper operation of the communication systems it is important to be able to determine the characteristics of these antennas. This thesis is about the analysis and design of conformal antennas using high frequency asymptotic methods. Commonly used eigenfunction solutions or numerical methods such as FDTD, FEM or MoM are difficult to use for arbitrarily shaped electrically large surfaces. However, the high frequency approximation approach together with an accurate ray tracing procedure offers a convenient solution for these surfaces. The geodesics (ray paths) on the surfaces are key parameters in the analysis and they are discussed in detail. In the first part of the thesis singly and doubly curved perfectly electrical conducting (PEC) surfaces are studied, with respect to the mutual coupling among aperture type elements. A synthesis problem is also considered where the effect of the mutual coupling is taken into account. As expected, the mutual coupling must be included in the synthesis procedure to be able to realize the prescribed pattern, especially in the shaped main lobe. Furthermore, the polarization of the antenna elements is very important when considering antennas on generally shaped surfaces. For such antennas the polarization must most likely be controlled in some way for a proper function. For verification of the results two experimental antennas were built at Ericsson Microwave Systems AB, Mölndal, Sweden. The first antenna is a circular cylinder with an array of rectangular waveguide fed apertures and the second antenna is a doubly curved surface (paraboloid) with circular waveguide fed apertures. It is found that it is possible to obtain very accurate results with the asymptotic method when it is combined with the Method of Moments, i.e. a hybrid method is used. The agreement compared to measurements is good at levels as low as –80 dB in many cases. The second part of the thesis is about the development of a high frequency approximation for surface field calculations on a dielectric covered PEC circular cylinder. When using conformal antennas in practice they have to be covered with a radome for protection and with the method developed here this cover can be included in the analysis. The method is a combination of two different solutions, one valid in the non-paraxial region of the cylinder and the other is valid in the paraxial region. The method is verified against measurements and reference results obtained from a spectral domain moment method code.

  • 49.
    Persson, Patrik
    KTH, Superseded Departments, Electromagnetic Theory.
    Calculating Geodesics on Doubly Curved Surfaces: The case of a General Paraboloid of Revolution2000Report (Other academic)
  • 50.
    Persson, Patrik
    KTH, Superseded Departments, Electromagnetic Theory.
    The Mutual Coupling between Apertures on Convex Cylinders1999In: Proceedings of radiovetenskap och kommunikation / [ed] Jan-Olof Gustafsson, Karlskrona: Högskolan i Karlskrona/Ronneby , 1999Conference paper (Other academic)
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