| 1. |
- Alayon Glasunov, Andrés, et al.
(författare)
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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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Ingår i: Progress in Electromagnetics Research B. - 1937-6472. ; :59, s. 205-217
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Tidskriftsartikel (refereegranskat)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.
(författare)
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On Some Optimal MIMO Antenna Coefficients in Multipath Channels
- 2011
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Ingår i: Progress in Electromagnetics Research B. - 1937-6472. ; 35, s. 87-109
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Tidskriftsartikel (refereegranskat)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.
(författare)
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Stabilization of Evanescent Wave Propagation Operators
- 2023
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Ingår i: Progress In Electromagnetics Research B. - 1937-6472. ; 101, s. 17-44
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Tidskriftsartikel (refereegranskat)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.
(författare)
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Design and Measurement-Based Evaluation of Multi-Antenna Mobile Terminals for LTE 3500 MHz Band
- 2013
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Ingår i: Progress in Electromagnetics Research B. - 1937-6472. ; 53:53, s. 241-266
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Tidskriftsartikel (refereegranskat)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.
(författare)
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Performance analysis of parallel non-orthogonal PEEC-based solver for EMC applications
- 2012
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Ingår i: Progress in Electromagnetics Research B. - 1937-6472. ; 41, s. 77-100
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Tidskriftsartikel (refereegranskat)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.
(författare)
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Approximative computation methods for monostatic scattering from axially symmetric objects
- 2017
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Ingår i: Progress In Electromagnetics Research B. - 1937-6472. ; 79, s. 127-147
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Tidskriftsartikel (refereegranskat)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
(författare)
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Equations of Motion of Interacting Classical Charged Particles and the Motion of an Electron outside a Long Solenoid
- 2023
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Ingår i: Progress in Electromagnetics Research B. - : The Electromagnetics Academy. - 1937-6472. ; 100, s. 39-53
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Tidskriftsartikel (refereegranskat)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.
(författare)
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Magnetic energy of surface currents on a torus
- 2013
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Ingår i: Progress in Electromagnetics Research B. - 1937-6472. ; :46, s. 357-378
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Tidskriftsartikel (refereegranskat)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.
(författare)
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Simulation of Rapid Voltage Edge Related Voltage Surges in Highly Inductive Windings with Frequency Dependent Parameters
- 2023
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Ingår i: Progress in Electromagnetics Research B. - : The Electromagnetics Academy. - 1937-6472. ; 99, s. 1-21
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Tidskriftsartikel (refereegranskat)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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