Limitations for the radiation Q of a small antenna enclosed in a spheroidal volume: Axial polarisation

Johan Sten (Corresponding Author), Päivi Koivisto, Arto Hujanen

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13 Citations (Scopus)

Abstract

Limitations for the radiation quality factor, Q, of a lossless linearly polarised structure which fits a spheroidal volume are searched for. The Q is evaluated by numerical integration of the evanescent energy outside the spheroid for the axially polarised field. The minimum Q for a prolate spheroid is found for a narrower radiation pattern than the sin θ-figure characteristic for an elementary dipole, while for the oblate, the minimum turns out for a broader pattern than that of an elementary dipole. The results agree with the previous theory, stating that the Q of a linearly polarised antenna can not be smaller than (ka)-3+ka-1, k being the wave number and a the radius of the smallest circumscribed sphere. The graphs showing the influence of the axial ratio on the radiation Q should be of practical interest in the design of wide band antennae of small electrical size as not only the maximum dimension of the antenna, but also its shape and polarisation is taken into account.
Original languageEnglish
Pages (from-to)198-204
Number of pages7
JournalAEÜ: International Journal of Electronics and Communications
Volume55
Issue number3
DOIs
Publication statusPublished - 2001
MoE publication typeA1 Journal article-refereed

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Polarization
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title = "Limitations for the radiation Q of a small antenna enclosed in a spheroidal volume: Axial polarisation",
abstract = "Limitations for the radiation quality factor, Q, of a lossless linearly polarised structure which fits a spheroidal volume are searched for. The Q is evaluated by numerical integration of the evanescent energy outside the spheroid for the axially polarised field. The minimum Q for a prolate spheroid is found for a narrower radiation pattern than the sin θ-figure characteristic for an elementary dipole, while for the oblate, the minimum turns out for a broader pattern than that of an elementary dipole. The results agree with the previous theory, stating that the Q of a linearly polarised antenna can not be smaller than (ka)-3+ka-1, k being the wave number and a the radius of the smallest circumscribed sphere. The graphs showing the influence of the axial ratio on the radiation Q should be of practical interest in the design of wide band antennae of small electrical size as not only the maximum dimension of the antenna, but also its shape and polarisation is taken into account.",
author = "Johan Sten and P{\"a}ivi Koivisto and Arto Hujanen",
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Limitations for the radiation Q of a small antenna enclosed in a spheroidal volume : Axial polarisation. / Sten, Johan (Corresponding Author); Koivisto, Päivi; Hujanen, Arto.

In: AEÜ: International Journal of Electronics and Communications, Vol. 55, No. 3, 2001, p. 198-204.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - Limitations for the radiation Q of a small antenna enclosed in a spheroidal volume

T2 - Axial polarisation

AU - Sten, Johan

AU - Koivisto, Päivi

AU - Hujanen, Arto

N1 - Project code: T9SU00034

PY - 2001

Y1 - 2001

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AB - Limitations for the radiation quality factor, Q, of a lossless linearly polarised structure which fits a spheroidal volume are searched for. The Q is evaluated by numerical integration of the evanescent energy outside the spheroid for the axially polarised field. The minimum Q for a prolate spheroid is found for a narrower radiation pattern than the sin θ-figure characteristic for an elementary dipole, while for the oblate, the minimum turns out for a broader pattern than that of an elementary dipole. The results agree with the previous theory, stating that the Q of a linearly polarised antenna can not be smaller than (ka)-3+ka-1, k being the wave number and a the radius of the smallest circumscribed sphere. The graphs showing the influence of the axial ratio on the radiation Q should be of practical interest in the design of wide band antennae of small electrical size as not only the maximum dimension of the antenna, but also its shape and polarisation is taken into account.

U2 - 10.1078/1434-8411-00030

DO - 10.1078/1434-8411-00030

M3 - Article

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JO - AEÜ: International Journal of Electronics and Communications

JF - AEÜ: International Journal of Electronics and Communications

SN - 1434-8411

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ER -