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On Methods to Determine Bounds on the Q-Factor for a Given Directivity
KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.ORCID iD: 0000-0001-7269-5241
KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
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2017 (English)In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 65, no 11, p. 5686-5696Article in journal (Refereed) Published
Abstract [en]

This paper revisit and extend the interesting case of bounds on the Q-factor for a given directivity for a small antenna of arbitrary shape. A higher directivity in a small antenna is closely connected with a narrow impedance bandwidth. The relation between bandwidth and a desired directivity is still not fully understood, not even for small antennas. Initial investigations in this direction have related the radius of a circumscribing sphere to the directivity, and bounds on the Q-factor have also been derived for a partial directivity in a given direction. In this paper, we derive lower bounds on the Q-factor for a total desired directivity for an arbitrarily shaped antenna in a given direction as a convex problem using semidefinite relaxation (SDR) techniques. We also show that the relaxed solution is also a solution of the original problem of determining the lower Q-factor bound for a total desired directivity. SDR can also be used to relax a class of other interesting nonconvex constraints in antenna optimization, such as tuning, losses, and front-to-back ratio. We compare two different new methods to determine the lowest Q-factor for arbitrary-shaped antennas for a given total directivity. We also compare our results with full electromagnetic simulations of a parasitic element antenna with high directivity.

Place, publisher, year, edition, pages
IEEE, 2017. Vol. 65, no 11, p. 5686-5696
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
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URN: urn:nbn:se:kth:diva-218217DOI: 10.1109/TAP.2017.2748383ISI: 000414047400003OAI: oai:DiVA.org:kth-218217DiVA, id: diva2:1160879
Note

QC 20171128

Available from: 2017-11-28 Created: 2017-11-28 Last updated: 2018-02-26Bibliographically approved

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Jonsson, B. Lars G.Shi, ShuaiWang, Lei

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