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

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

    Research output: Contribution to journalArticleScientificpeer-review

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    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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    Antennas
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    Cite this

    @article{443bf11520a64e958987c75e5dbf7ac3,
    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",
    note = "Project code: T9SU00034",
    year = "2001",
    doi = "10.1078/1434-8411-00030",
    language = "English",
    volume = "55",
    pages = "198--204",
    journal = "AE{\"U}: International Journal of Electronics and Communications",
    issn = "1434-8411",
    publisher = "Urban und Fischer Verlag Jena",
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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

    N2 - 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.

    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

    VL - 55

    SP - 198

    EP - 204

    JO - AEÜ: International Journal of Electronics and Communications

    JF - AEÜ: International Journal of Electronics and Communications

    SN - 1434-8411

    IS - 3

    ER -