| 1. |
- Alayon Glasunov, Andrés, et al.
(author)
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Experimental characterization of the propagation channel along a very large virtual array in a reverberation chamber
- 2014
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In: Progress in Electromagnetics Research B. - 1937-6472. ; :59, s. 205-217
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Journal article (peer-reviewed)abstract
- 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.
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| 2. |
- Alayon Glazunov, Andres, 1969-, et al.
(author)
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On Some Optimal MIMO Antenna Coefficients in Multipath Channels
- 2011
-
In: Progress in Electromagnetics Research B. - 1937-6472. ; 35, s. 87-109
-
Journal article (peer-reviewed)abstract
- 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.
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| 3. |
- Andersson, Michael, et al.
(author)
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Stabilization of Evanescent Wave Propagation Operators
- 2023
-
In: Progress In Electromagnetics Research B. - 1937-6472. ; 101, s. 17-44
-
Journal article (peer-reviewed)abstract
- This paper presents a stabilized scheme that solves the wave propagation problem in a general bianisotropic, stratified medium. The method utilizes the concept of propagators, i.e., the wave propagation operators that map the total tangential electric and magnetic fields from one plane in the slab to another. The scheme transforms the propagator approach into a scattering matrix form, where a spectral decomposition of the propagator enables separation of the exponentially growing and decaying terms in order to obtain a well-conditioned formulation. Multilayer structures can be handled in a stable manner using the dissipative property of the Redheffer star product for cascading scattering matrices. The re ection and transmission dyadics for a general bianisotropic medium with an isotropic half space on both sides of the slab are presented in a coordinate-independent dyadic notation, as well as the re ection dyadic for a bianisotropic slab with perfect electric conductor backing (PEC). Several numerical examples that illustrate the performance of the stabilized algorithm are presented.
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| 4. |
- Azremi, Abdullah Al-Hadi, et al.
(author)
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Design and Measurement-Based Evaluation of Multi-Antenna Mobile Terminals for LTE 3500 MHz Band
- 2013
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In: Progress in Electromagnetics Research B. - 1937-6472. ; 53:53, s. 241-266
-
Journal article (peer-reviewed)abstract
- Design of multi-element antennas for small mobile terminals operating at higher frequencies remains challenging despite smaller antenna dimension and possibility of achieving electrically large separation between them. In this paper, the importance of the type of radiating elements operating at 3400-3600 MHz and their locations on the terminal chassis are highlighted. An isotropic radiation pattern that receives incoming signals from arbitrary directions is obtained by combining the radiation patterns of multiple antennas with localized chassis current distribution. Four multiport antennas configurations with two- and eight-element antennas are designed and evaluated experimentally in indoor propagation environments. Our proposed designs of multi-element antennas provide the highest MIMO channel capacity compared to their counterparts using antennas with less localized chassis current distribution, even in the presence of user's hand.
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| 5. |
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| 6. |
- Daroui, Danesh, et al.
(author)
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Performance analysis of parallel non-orthogonal PEEC-based solver for EMC applications
- 2012
-
In: Progress in Electromagnetics Research B. - 1937-6472. ; 41, s. 77-100
-
Journal article (peer-reviewed)abstract
- 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.
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| 7. |
- Ericsson, Andreas, et al.
(author)
-
Approximative computation methods for monostatic scattering from axially symmetric objects
- 2017
-
In: Progress In Electromagnetics Research B. - 1937-6472. ; 79, s. 127-147
-
Journal article (peer-reviewed)abstract
- Two approximation methods are presented for fast calculations of the monostatic scattering from axially symmetric scatterers coated with electromagnetic absorbers. The methods are designed for plane wave illumination parallel to the axis of rotation of the scatterer. The first method is based on simulating the scattering of a perfect electric conductor (PEC) enclosing the absorber coated scatterer, and multiplying the result with the squared magnitude of the absorber reflection coefficient in a planar scenario. The second method is based on simulating the scattering scenario in a physical optics (PO) solver, where the electromagnetic absorber is treated as reflection dyadic at the outer surface of the scatterer. Both methods result in a significant acceleration in computation speed in comparison to full wave methods, where the PO method carries out the computations in a number of seconds. The monostatic scattering from different geometries have been investigated, and parametric sweeps were carried out to test the limits where the methods yield accurate results. For specular reflections, the approximation methods yield very accurate results compared to full wave simulations when the radius of curvature is on the order of half a wavelength or larger of the incident signal. It is also concluded that the accuracy of the two methods varies depending on what type of absorber is applied to the scatterer, and that absorbers based on "volume losses" such as a carbon doped foam absorber and a thin magnetic absorber yield better results than absorbers based on resistive sheets, such as a Salisbury absorber.
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| 8. |
- Essén, Hanno
(author)
-
Equations of Motion of Interacting Classical Charged Particles and the Motion of an Electron outside a Long Solenoid
- 2023
-
In: Progress in Electromagnetics Research B. - : The Electromagnetics Academy. - 1937-6472. ; 100, s. 39-53
-
Journal article (peer-reviewed)abstract
- The equation of motion for a test particle moving in given fixed external fields is analyzed and compared to the corresponding equation of motion derived from the Darwin Lagrangian for a system of interacting charged particles. The two approaches agree as long as the part of the electric field that arises from the partial time derivative of the vector potential is taken into account. It is, however, only via the Darwin approach that the origin of this field can be understood as arising from a breakdown of the test particle approximation. Applying the formalism to an electron moving outside a long solenoid results in a classical analog of the Aharonov-Bohm effect.
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| 9. |
- Essén, Hanno, et al.
(author)
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Magnetic energy of surface currents on a torus
- 2013
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In: Progress in Electromagnetics Research B. - 1937-6472. ; :46, s. 357-378
-
Journal article (peer-reviewed)abstract
- 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.
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| 10. |
- Felicetti, Roberto, 1972-, et al.
(author)
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Simulation of Rapid Voltage Edge Related Voltage Surges in Highly Inductive Windings with Frequency Dependent Parameters
- 2023
-
In: Progress in Electromagnetics Research B. - : The Electromagnetics Academy. - 1937-6472. ; 99, s. 1-21
-
Journal article (peer-reviewed)abstract
- Many static and rotating electric energy converters make use of inductive coils as filters, reactive loads or exciters, where a sudden variation of the magnetizing current can produce severe overvoltage with potential subsequent insulation damage. In some applications the overvoltage is the result of a superposition of travelling voltage waves in a supplying line. Traditional tools for studying such phenomena are based on ordinary differential equations that can heavily handle variable parameters, especially if they change according to the rapidity of the observed overvoltage. In this paper the transient voltage distribution in the excitation winding of a salient pole synchronous generator is simulated by solving the problem entirely in the frequency domain, i.e., without any use of the traditional ordinary differential equations solvers. Thismakesit possible to tune the parameters of a simplified electric model to the frequency response of the studied winding. It is shown that for highly inductive windings a single transmission line model with frequency dependent parameters can reproduce voltage transients very accurately, in a broad interval of frequency, relevant for power electronics and electromagnetic compatibility applications. Furthermore, the paper presents the experimental setup which has been needed for generating the fast varying voltage edges.
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| 11. |
- Fiolhais, Miguel, et al.
(author)
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Magnetic field and current are zero inside ideal conductors
- 2011
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In: Progress in Electromagnetics Research B. - 1937-6472. ; 27, s. 187-212
-
Journal article (peer-reviewed)abstract
- 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.
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| 12. |
- Hassan, Emadeldeen, 1979-, et al.
(author)
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Patch and ground plane design of microstrip antennas by material distribution topologly optimization
- 2014
-
In: Progress in Electromagnetics Research B. - : Electromagnetics Academy. - 1937-6472. ; 59, s. 89-102
-
Journal article (peer-reviewed)abstract
- 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.
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| 13. |
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| 14. |
- Johansson, Markus, 1978, et al.
(author)
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Comparison between Two Phase Retrieval Methods for Electromagnetic Source Modeling
- 2011
-
In: Progress in Electromagnetics Research B. - 1937-6472. ; 30, s. 239-253
-
Journal article (peer-reviewed)abstract
- Phase-retrieval from measured phaseless field data is of interest for various applications including electromagnetic dosimetry, electromagnetic compatibility investigations, near-field to far-field transformations and antenna diagnostics. In this study two phaseretrieval methods are compared. The first method, the adjoint field method, employs a gradient-based optimization algorithm based on the adjoint fields. The second method, the phase angle gradient method, uses an optimization algorithm based on the phase angle gradients of a functional. The methods are tested with numerical test cases and the phase angle gradient method is found to retrieve the phase with the best accuracy. Moreover it gives results that agree well with correct phase.
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| 15. |
- Johansson, Markus, 1978, et al.
(author)
-
Performance Evaluation of Phase-Angle Gradient Method for Phase Retrieval based on Low-Frequency amplitude-Only Near-Field Data
- 2010
-
In: Progress in Electromagnetics Research B. - 1937-6472. ; 25:25, s. 113-130
-
Journal article (peer-reviewed)abstract
- The Phase Angle Gradient Method (PAGM) is a recent technique developed for phase retrieval based on amplitude-only measurement data. Preliminary results have shown that the PAGM is able to perform phase retrieval at 100MHz with accurate phase information based on measured fIeld components on three planar surfaces. In this paper, a performance evaluation of the PAGM under different conFigurations is conducted. Phase retrieval based on field measurements for different plane sizes and separations between the planes are studied rigorously. In addition, the PAGM is tested for different initial phase distributions. The results show that the PAGM is capable of retrieving phase information even if the separation between the measurement planes is small in terms of wavelengths.
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| 16. |
- Li, Bing, et al.
(author)
-
An Efficient Method for Solving Frequency Responses of Power-Line Networks
- 2015
-
In: Progress in Electromagnetics Research B. - : EMW Publishing. - 1937-6472. ; 62:1, s. 303-317
-
Journal article (peer-reviewed)abstract
- 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.
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| 17. |
- Marcusson, Birger, et al.
(author)
-
Harmonically Time Varying, Traveling Electromagnetic Fields along a Laminate Approximated by a Homogeneous, Anisotropic Block with Infinite Length
- 2017
-
In: Progress in Electromagnetics Research B. - : The Electromagnetics Academy. - 1937-6472. ; 79, s. 65-81
-
Journal article (peer-reviewed)abstract
- 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.
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| 18. |
- Marcusson, Birger, et al.
(author)
-
Harmonically Time Varying, Traveling Electromagnetic Fields along a Plate and a Laminate with a Rectangular Cross Section, Isotropic Materials and Infinite Length
- 2017
-
In: Progress in Electromagnetics Research B. - 1937-6472. ; 77, s. 117-136
-
Journal article (peer-reviewed)abstract
- 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.
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| 19. |
- Månsson, Daniel
(author)
-
On the Optimization of Halbach Arrays as Energy Storage Media
- 2015
-
In: Progress in Electromagnetics Research B. - : EMW Publishing. - 1937-6472. ; 62:1, s. 277-288
-
Journal article (peer-reviewed)abstract
- 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.
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| 20. |
- Månsson, Daniel
(author)
-
On the Suitability of Using Halbach Arrays as Potential Energy Storage Media
- 2014
-
In: Progress in Electromagnetics Research B. - : EMW Publishing. - 1937-6472. ; 58, s. 151-166
-
Journal article (peer-reviewed)abstract
- 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.
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| 21. |
- Nordebo, Sven, 1963-, et al.
(author)
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A priori modeling for gradient based inverse scattering algorithms
- 2009
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In: Progress in Electromagnetics Research B. - 1937-6472. ; 16, s. 407-432
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Journal article (peer-reviewed)abstract
- 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.
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| 22. |
- Nordebo, Sven, et al.
(author)
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A Quasi-Static Electromagnetic Analysis for Experiments with Strong Permanent Magnets
- 2014
-
In: Progress in Electromagnetics Research B. - 1937-6472. ; 61, s. 1-16
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Journal article (peer-reviewed)abstract
- 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.
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| 23. |
- Persson, Kristin, et al.
(author)
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Reconstruction and visualization of equivalent currents on a radome using an integral representation formulation
- 2010
-
In: Progress In Electromagnetics Research B. - 1937-6472. ; 20, s. 65-90
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Journal article (peer-reviewed)abstract
- In this paper an inverse source problem is investigated. The measurement set-up is a reflector antenna covered by a radome. Equivalent currents are reconstructed on a surface shaped as the radome in order to diagnose the radome's interaction with the radiated field. To tackle this inverse source problem an analysis of a full-wave integral representation, with the equivalent currents as unknowns, is used. The extinction theorem and its associated integral equation ensure that the reconstructed currents represent sources within the radome. The axially symmetric experimental set-up reduces the computational complexity of the problem. The resulting linear system is inverted by using a singular value decomposition. We visualize how the presence of the radome alters the components of the equivalent currents. The method enables us to determine the phase shift of the field due to the transmission of the radome, i.e., the IPD (insertion phase delay). Also, disturbances due to defects, not observable in the measured near field, are localized in the equivalent currents.
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| 24. |
- Shestopalov, Yury, 1953-, et al.
(author)
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On a rigorous proof of the existence of complex waves in a dielectric waveguide of circular cross section
- 2018
-
In: Progress in Electromagnetics Research B. - 1937-6472. ; 82, s. 137-164
-
Journal article (peer-reviewed)abstract
- 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.
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| 25. |
- Shestopalov, Yury V., 1953-
(author)
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Resonant states in waveguide transmission problems
- 2015
-
In: Progress in Electromagnetics Research B. - New York : Institute of Electrical and Electronics Engineers (IEEE). - 1937-6472. - 9789090086286 ; 64:1, s. 119-143
-
Journal article (peer-reviewed)abstract
- 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.
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| 26. |
- Sjöberg, Daniel
(author)
-
Determination of propagation constants and material data from waveguide measurements
- 2009
-
In: Progress In Electromagnetics Research B. - 1937-6472. ; 12, s. 163-182
-
Journal article (peer-reviewed)abstract
- This paper presents an analysis with the aim of characterizing the electromagnetic properties of an arbitrary linear, bianisotropic material inside a metallic waveguide. The result is that if the number of propagating modes is the same inside and outside the material under test, it is possible to determine the propagation constants of the modes inside the material by using scattering data from two samples with different lengths. Some information can also be obtained on the cross-sectional shape of the modes, but it remains an open question if this information can be used to characterize the material. The method is illustrated by numerical examples, determining the complex permittivity for lossy isotropic and anisotropic materials.
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| 27. |
- Sten, Johan C.-E., et al.
(author)
-
Low-frequency scattering analysis and homogenisation of split-ring elements
- 2011
-
In: Progress In Electromagnetics Research B. - 1937-6472. ; 35, s. 187-212
-
Journal article (peer-reviewed)abstract
- A key structure in so-called metamaterial mediums is the elementary split-ring resonator. We consider in this paper the low-frequency electromagnetic scattering by a split-ring particle modelled as a perfectly conducting wire ring, furnished with a narrow gap, and derive analytical solutions for the electric and magnetic dipole moments for different kinds of incidence and polarisation in the quasi-static approximation. Through a vectorial homogenisation process, the expressions discovered for the dipole moments and the related polarisability dyadics are linked with the macroscopic constitutive equations for the medium. We further show that the condition for resonance of a medium consisting of simple split-rings cannot be achieved by means of the given quasi-static terms without violating the underlying assumptions of homogenisation. Nevertheless, the results are applicable for sparse medium of rings, and we derive numerical guidelines for the applicability with some examples of the effect of the considered split-ring medium on electromagnetic wave propagation.
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| 28. |
- Takook, Pegah, 1982, et al.
(author)
-
A computational study using time reversal focusing for hyperthermia treatment planning
- 2017
-
In: Progress in Electromagnetics Research B. - 1937-6472. ; 73:1, s. 117-130
-
Journal article (peer-reviewed)abstract
- In hyperthermia treatment planning (HTP) the goal is to find the amplitudes and phases of antennas in the applicator to efficiently heat the tumor. To do this prior information regarding tumor characteristics such as the size, position and geometry, in addition to an exact model of the hyperthermia applicator is needed. Based on this information, the optimal frequency of operation can be determined. In this paper the optimum frequency for hyperthermia treatment based on the tumor and applicator characteristics, using time reversal as the focusing technique, is studied. As prior information, we consider tumor size and position, the number of the antennas in the applicator and the frequency characteristics. The obtained optimal frequency range is found using hyperthermia quality indicator values calculated from simulations. We also determine the optimum position of the virtual source in the initial step of the time reversal method to increase the quality of the treatment.
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| 29. |
- Winges, Johan, 1987, et al.
(author)
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Multi-objective optimization of wireless power transfer systems with magnetically coupled resonators and nonlinear loads
- 2019
-
In: Progress in Electromagnetics Research B. - 1937-6472. ; 83:2019, s. 25-42
-
Journal article (peer-reviewed)abstract
- © 2019 Progress In Electromagnetics Research B. We present an optimization procedure for wireless power transfer (WPT) applications and test it numerically for a WPT system design with four resonant circuits that are magnetically coupled by coaxial coils in air, where the magnetic field problem is represented by a fully populated inductance matrix that includes all magnetic interactions that occur between the coils. The magnetically coupled resonators are fed by a square-wave voltage generator and loaded by a rectifier followed by a smoothing filter and a battery. We compute Pareto fronts associated with a multi-objective optimization problem that contrasts: 1) the system efficiency; and 2) the power delivered to the battery. The optimization problem is constrained in terms of: 1) the physical construction of the system and its components; 2) the root-mean-square values of the currents and voltages in the circuit; and 3) bounds on the overtones of the currents in the coils in order assure that the WPT system mainly generates magnetic fields at the operating frequency. We present optimized results for transfer distances from 0.8 to 1.6 times the largest coil radius with a maximum power transfer from 4 kW to 9 kW at 85 kHz, which is achieved at an efficiency larger than 90%.
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