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Miloslav Capek

Bio: Miloslav Capek is an academic researcher from Czech Technical University in Prague. The author has contributed to research in topics: Antenna (radio) & Method of moments (statistics). The author has an hindex of 20, co-authored 132 publications receiving 1284 citations.


Papers
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Journal ArticleDOI
TL;DR: In this paper, a new formula for the evaluation of the modal radiation Q factor is derived, which is based on the electric field integral equation, Delaunay triangulation, method of moments, Rao-Wilton-Glisson basis function and the theory of characteristic modes.
Abstract: A new formula for the evaluation of the modal radiation Q factor is derived. The total Q of selected structures is to be calculated from the set of eigenmodes with associated eigen-energies and eigen-powers. Thanks to the analytical expression of these quantities, the procedure is highly accurate, respecting arbitrary current densities flowing along the radiating device. The electric field integral equation, Delaunay triangulation, method of moments, Rao-Wilton-Glisson basis function and the theory of characteristic modes constitute the underlying theoretical background. In terms of the modal radiation Q, all necessary relations are presented and the essential points of implementation are discussed. Calculation of the modal energies and Q factors enable us to study the effect of the radiating shape separately to the feeding. This approach can be very helpful in antenna design. A few examples are given, including a thin-strip dipole, two coupled dipoles a bowtie antenna and an electrically small meander folded dipole. Results are compared with prior estimates and some observations are discussed. Good agreement is observed for different methods.

86 citations

Journal ArticleDOI
TL;DR: In this paper, the Rao-Wilton-Glisson basis representation is used to simplify the underlying algebra while still allowing surface current regions of arbitrary shape to be treated, and it is shown that the optimal current can, in principle, be found as a combination of a few eigenmodes.
Abstract: An optimization problem has been formulated to find a resonant current extremizing various antenna parameters. The method is presented on, but not limited to, particular cases of gain $G$ , quality factor $Q$ , gain to quality factor ratio $G/Q$ , and radiation efficiency $\eta $ of canonical shapes with conduction losses explicitly included. The Rao–Wilton–Glisson basis representation is used to simplify the underlying algebra while still allowing surface current regions of arbitrary shape to be treated. By switching to another basis generated by a specific eigenvalue problem, it is finally shown that the optimal current can, in principle, be found as a combination of a few eigenmodes. The presented method constitutes a general framework in which the antenna parameters, expressed as bilinear forms, can automatically be extremized.

82 citations

Journal ArticleDOI
TL;DR: It is observed that small increases in Q-factor away from its lower bound allow for dramatic increases in efficiency toward its upper bound, and the tradeoff evaluation method is valid for studying arbitrary antenna geometries.
Abstract: The tradeoff between radiation efficiency and antenna bandwidth, expressed in terms of Q-factor for small antennas, is formulated as a multiobjective optimization problem in current distributions of predefined support. Variants on the problem are constructed to demonstrate the consequences of requiring a self-resonant current as opposed to the one tuned by an external reactance. The tradeoffs are evaluated for sample problems and the resulting Pareto-optimal sets reveal the relative cost of valuing low radiation Q-factor over high efficiency, the cost in efficiency to require a self-resonant current, the effects of lossy parasitic loading, and other insights. Observations are drawn from the sample problems selected, though the tradeoff evaluation method is valid for studying arbitrary antenna geometries. In the examples considered here, we observe that small increases in Q-factor away from its lower bound allow for dramatic increases in efficiency toward its upper bound.

70 citations

Journal ArticleDOI
TL;DR: An advanced tracking procedure has been developed to deal with noisy modes, non-continuous behavior of eigenvalues, mode swapping etc.
Abstract: A new method for tracking characteristic numbers and vectors appearing in the Characteristic Mode Theory is presented in this paper. The challenge here is that the spectral decomposition of the moment impedance-matrix doesn't always produce well ordered eigenmodes. This issue is addressed particularly to flnite numerical accuracy and slight nonsymmetry of the frequency- dependent matrix. At speciflc frequencies, the decomposition problem might be ill-posed and non-uniquely deflned as well. Hence an advanced tracking procedure has been developed to deal with noisy modes, non-continuous behavior of eigenvalues, mode swapping etc. Proposed method has been successfully implemented into our in-house Characteristic Mode software tool for the design of microstrip patch antennas and tested for some interesting examples.

61 citations

Journal ArticleDOI
TL;DR: In this article, the problem of minimizing the quality factor of arbitrarily shaped radiators with respect to the minimum quality factor was formulated as a dual problem and solved using modal decomposition and group theory.
Abstract: Optimal currents on arbitrarily shaped radiators with respect to the minimum quality factor are found using a simple and efficient procedure. The solution starts with a reformulation of the problem of minimizing quality factor $Q$ as an alternative, so-called dual, problem. Taking advantage of modal decomposition and group theory, it is shown that the dual problem can easily be solved and always results in minimal quality factor $Q$ . Moreover, the optimization procedure is generalized to minimize quality factor $Q$ for embedded antennas, with respect to the arbitrarily weighted radiation patterns, or with prescribed magnitude of the electric and magnetic near fields. The obtained numerical results are compatible with previous results based on the composition of modal currents, convex optimization, and quasi-static approximations; however, using the methodology in this paper, the class of solvable problems is significantly extended.

57 citations


Cited by
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Book ChapterDOI
01 Jan 2007

1,089 citations

01 Jan 2016
TL;DR: The electrodynamics of continuous media is universally compatible with any devices to read and is available in the book collection an online access to it is set as public so you can get it instantly.
Abstract: Thank you for reading electrodynamics of continuous media. Maybe you have knowledge that, people have look numerous times for their chosen books like this electrodynamics of continuous media, but end up in infectious downloads. Rather than reading a good book with a cup of tea in the afternoon, instead they cope with some malicious bugs inside their computer. electrodynamics of continuous media is available in our book collection an online access to it is set as public so you can get it instantly. Our book servers saves in multiple locations, allowing you to get the most less latency time to download any of our books like this one. Kindly say, the electrodynamics of continuous media is universally compatible with any devices to read.

898 citations

01 Jan 2016
TL;DR: This rfid handbook fundamentals and applications in contactless smart cards and identification helps people to read a good book with a cup of coffee in the afternoon instead of juggled with some malicious bugs inside their laptop.
Abstract: Thank you for reading rfid handbook fundamentals and applications in contactless smart cards and identification. As you may know, people have search numerous times for their chosen novels like this rfid handbook fundamentals and applications in contactless smart cards and identification, but end up in malicious downloads. Rather than reading a good book with a cup of coffee in the afternoon, instead they juggled with some malicious bugs inside their laptop.

570 citations

Journal Article
TL;DR: The Micro-Doppler Effect in Radar by V. C. Chen as discussed by the authors is a book review of "The Micro Doppler effect in radar" by Chen et al. 2011. 290pp + diskette.
Abstract: This is a book review of 'The Micro-Doppler Effect in Radar' by V. C. Chen. Artech House, 16 Sussex Street, London, SW1V 4RW, UK. 2011. 290pp + diskette. Illustrated. £90. ISBN 978-1-60807-057-2.

439 citations

01 Jan 2016

353 citations