Research Articles (Electrical and Electronic Engineering)

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Browsing Research Articles (Electrical and Electronic Engineering) by Subject "Antenna radiation patterns"

Now showing 1 - 4 of 4
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    Constant radiation characteristics for log-periodic dipole array antennas
    (Institute of Electrical and Electronics Engineers, 2014) Lehmensiek, Robert; De Villiers, Dirk I. L.
    Given the correct terminal voltages on each element of a log-periodic dipole array constant radiation characteristics can be achieved for an omni-directional radiation pattern. In this communication it is shown that this can only be achieved through optimization, correcting a previously reported oversimplification which resulted in an analytical approach being tractable. This oversimplification assumed that vanishing terminal currents on a dipole’s terminal/feed element implies no radiation from that dipole. This is clearly non-physical because, zeroing the terminal current on a dipole’s feed element is the same as disconnecting its two arms, while having no radiation from that dipole implies that in effect both arms be entirely removed. We show that the effect of currents induced in the disconnected arms of a dipole cannot in general be ignored.
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    Modeling of the radiation pattern of a pair of thin circular-arc dipoles over an infinite ground plane
    (Institute of Electrical and Electronics Engineers, 2013) De Villiers, Dirk I. L.; Lehmensiek, Robert
    This communication presents a model of the radiation pattern of two circular-arc dipoles above an infinite perfectly electrically conducting ground plane. A Fourier expansion is used to describe the currents on the wires, and thin circular loop antenna theory is used to derive the radiation patterns. The results are compared to Method of Moments simulations, and it is shown that higher order cosinusoidal harmonics are required in the current model to achieve good correlation between the radiation pattern models and the full wave simulations.
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    Multivariate adaptive sampling of parameterized antenna responses
    (Institute of Electrical and Electronics Engineers, 2017) Mutonkole, Ngoy; De Villiers, Dirk I. L.
    ENGLISH ABSTRACT: We present a robust method to adaptively construct parameterized models of the full radiation patterns of antennas and the associated S-parameters. The method sequentially selects points (geometric parameters of the antenna and frequency) such that an accurate model is obtained over a constrained multivariate parameter space. The algorithm consists of a balance between exploration and exploitation of the parameter space, resulting in a near optimal coverage of the design space, with some emphasis being placed in regions of the parameter space where the patterns or S-parameters vary rapidly. In addition, the technique is equipped with a measure of absolute error control. The proposed method is validated through pertinent numerical examples.
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    Parametric modeling of radiation patterns and scattering parameters of antennas
    (Institute of Electrical and Electronics Engineers, 2016) Mutonkole, Ngoy; Samuel, Elizabeth Rita; De Villiers, Dirk I. L.; Dhaene, Tom
    This paper describes a data-driven method to model the radiation patterns (over a large angular region) and scattering parameters of antennas as a function of the geometry of the antenna. The radiation pattern model consists of a linear combination of characteristic basis function patterns (CBFPs), where the expansion coefficients of the CBFPs are functions of geometrical features of the antenna. Scattering parameters are modeled by means of parameterized state-space matrices. The obtained models are quick to evaluate and are thus suitable for design activities where multiple simulations are required. The proposed method is validated through illustrative examples.