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Lund University Lund University Publications2000-01-01T00:00+00:001dailyEnergy Stored by Radiating Systems
https://lup.lub.lu.se/search/publication/249a71ee-af0d-44e0-bbd5-24c0c424b61a
Schab, KurtJelinek, LukasCapek, MiloslavEhrenborg, CasimirTayli, DorukVandenbosch, Guy A.E.Gustafsson, Mats2018-02-17Though commonly used to calculate Q-factor and fractional bandwidth, the energy stored by radiating systems (antennas) is a subtle and challenging concept that has perplexed researchers for over half a century. Here, the obstacles in defining and calculating stored energy in general electromagnetic systems are presented from first principles as well as using demonstrative examples from electrostatics, circuits, and radiating systems. Along the way, the concept of unobservable energy is introduced to formalize such challenges. Existing methods of defining stored energy in radiating systems are then reviewed in a framework based on technical commonalities rather than chronological order. Equivalences between some methods under common assumptions are highlighted, along with the strengths, weaknesses, and unique applications of certain techniques. Numerical examples are provided to compare the relative margin between methods on several radiating structures.http://lup.lub.lu.se/record/249a71ee-af0d-44e0-bbd5-24c0c424b61ahttp://dx.doi.org/10.1109/ACCESS.2018.2807922scopus:85042186868engIEEE Access; 6, pp 10553-10568 (2018)ISSN: 2169-3536Annan elektroteknik och elektronikantenna theoryElectromagnetic theoryenergy storagePoynting’s theoremQ-factorEnergy Stored by Radiating Systemscontributiontojournal/articleinfo:eu-repo/semantics/articletextMinimization of Antenna Quality Factor
https://lup.lub.lu.se/search/publication/9201f4e1-47af-4cde-a4b3-10481daa5a70
Capek, MiloslavGustafsson, MatsSchab, Kurt2017-08Optimal 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 composition of modal currents, convex optimization, and quasistatic approximations; however, using the methodology in this paper, the class of solvable problems is significantly extended.http://lup.lub.lu.se/record/9201f4e1-47af-4cde-a4b3-10481daa5a70http://dx.doi.org/10.1109/TAP.2017.2717478scopus:85021824067wos:000407397600031engIEEE Transactions on Antennas and Propagation1963-01-01+01:00; 65(8), pp 4115-4123 (2017)ISSN: 0018-926XTelekommunikationAntenna theoryAntennasConvex functionsEigenvalues and eigenfunctionseigenvalues and eigenfunctionselectromagnetic theoryImpedanceMinimizationOptimizationoptimization methodsQ factorQ-factorMinimization of Antenna Quality Factorcontributiontojournal/articleinfo:eu-repo/semantics/articletext