Supergain antennas: possibilities and problems

Haviland, R. P.

doi:10.1109/74.414725

Cited by 23 publications

(10 citation statements)

References 6 publications

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“…In recent decades, with the rapid development of wireless applications, electrically small antennas (ESAs) with high directivity have become desirable. Hence, this is a hot topic in antenna engineering and a variety of successful efforts have been reported [1][2][3]. One effective approach is to combine two or three ESAs into a compact array [2,[4][5][6][7][8].…”

Section: Introductionmentioning

confidence: 99%

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Compact, two‐element array with high broadside directivity

Tang

Ziolkowski

2013

IET Microwaves, Antennas & Propagation

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A combination of two high directivity, electrically small, slot‐modified conducting disc‐augmented Egyptian axe dipole (EAD) antennas is investigated to achieve interesting broadside radiation properties, including a high broadside directivity and front‐to‐back ratio. Their array arrangement is guided by a simple two‐element dipole model. The parasitic conducting disc associated with each EAD antenna is modified only slightly from their original single‐element dimensions to preserve nearly complete matching to their sources, to accommodate the coupling between the two elements and to maximise the array pattern characteristics. Parameter studies lead to a final design, whose simulation results demonstrate that the two‐element array has outstanding performance characteristics, including a 9.98 dB broadside directivity, an 88.19% radiation efficiency, a 20.03 dB front‐to‐back‐ratio, a − 22.42 dB mutual coupling level, more than a 30 dB level of polarisation purity, and good impedance matching to their respective 50 Ω sources, despite each antenna being electrically small, that is, ka < 1, and the distance between the centre of each element being only slightly larger than a half wavelength.

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Section: Introductionmentioning

confidence: 99%

“…The maximum directivity along each lobe becomes equal when d = 1.0λ 0 . The half-power beamwidth continues to be narrow, as specified by (2). However, the appearance of the lobes along the y-axis is detrimental to the goal of achieving a high broadside directivity.…”

Section: Introductionmentioning

confidence: 99%

Compact, two‐element array with high broadside directivity

Tang

Ziolkowski

2013

IET Microwaves, Antennas & Propagation

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“…However, large mismatches and low radiation resistances prevented the practical realization of significant supergain from these arrays.) Thus the 1995 statement of Haviland [1995] that “the small high‐gain and highly directive beam antenna remains ‘pie in the sky'” describes the present state of the art of electrically small supergain antennas (including end‐fire antenna arrays with separately fed elements and parasitic arrays with a single‐feed element combined with parasitic elements). It also sets the stage for the present paper in which we document the theory, computer simulations, and experimental measurements for separately fed and singly fed (parasitic), highly efficient, two‐element, electrically small supergain end‐fire arrays with free space gains of 6 to 7 dB.…”

Section: Introductionmentioning

confidence: 99%

Electrically small supergain end‐fire arrays

et al. 2008

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[1] The theory, computer simulations, and experimental measurements are presented for electrically small, two-element supergain arrays with near-optimal end-fire gains of 7 dB. We show how the difficulties of narrow tolerances, large mismatches, low radiation efficiencies, and reduced scattering of electrically small parasitic elements are overcome by using electrically small resonant antennas as the elements in both separately driven and singly driven (parasitic), two-element, electrically small supergain end-fire arrays. Although rapidly increasing narrow tolerances prevent the practical realization of the maximum theoretically possible end-fire gain of electrically small arrays with many elements, the theory and preliminary numerical simulations indicate that near-maximum supergains are also achievable in practice for electrically small arrays with three (and possibly more) resonant elements if the decreasing bandwidth with increasing number of elements can be tolerated.

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“…In theory, an unlimited superdirective response can be obtained by exciting higher order modes (HOMs) [31], [32]. However, practical implementations of HOM approaches are hindered by increasingly narrower bandwidths; the fact that they are ill-posed solutions and, hence, are extremely sensitive to fabrication tolerances; and the dramatic damping that occurs when realistic losses are included [18], [33], [34]. Therefore, we will adhere here to the strategy of enhancing the directivity to reach the upper bounds by achieving a balanced combination of perpendicular electric and magnetic dipole moments, i.e., emulating a Huygens source.…”

Section: Electrically Small Forward-scattering Particlesmentioning

confidence: 99%

Upper Bounds on Scattering Processes and Metamaterial-Inspired Structures That Reach Them

Liberal

Ederra

Gonzalo

et al. 2014

IEEE Trans. Antennas Propagat.

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The physical limitations on time-harmonic scattering processes are investigated on the basis of the optical theorem. Previously derived least upper bounds on the total scattering and absorption cross-sections are obtained from it in a straightforward manner. In addition, it reveals a practical upper bound for the bistatic cross-section when evaluated in any direction. It is proved further that the maximum upper bound of the bistatic cross-section occurs in the forward scattering direction and that the corresponding upper bound for the backscattering direction is four times smaller than this maximum value. Metamaterialinspired electrically small antennas and scattering particles that approach these upper bounds are demonstrated. These examples numerically validate the derived upper bounds, as well as illustrate the important physical principles underlying them.

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Supergain antennas: possibilities and problems

Cited by 23 publications

References 6 publications

Compact, two‐element array with high broadside directivity

Compact, two‐element array with high broadside directivity

Electrically small supergain end‐fire arrays

Upper Bounds on Scattering Processes and Metamaterial-Inspired Structures That Reach Them

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