Investigation of Overcoming the Chu Lower Bound on Quality Factor for Antennas Tuned with Highly Dispersive Lossy Material

<div>A highly miniaturized three-dimensional spherical folded dipole antenna has been reported, for which inherent impedance matching is achieved with respect to a practical source impedance by employing a simple series-LC loading combination, thereby engineering its input impedance. In order to maximize its bandwidth, the miniaturized antenna employs a bifilar spherical helix that maximizes use of the volume of the corresponding Chu sphere. Full-wave simulations show that the resulting antenna demonstrates excellent impedance matching and over 95% radiation efficiency even when miniaturized by 85% in comparison to a resonant dipole operating at the same frequency. Furthermore, various quality-factor definitions for the miniaturized spherical folded dipole antenna were estimated. It is observed that, owing to the use of proximate but non-overlapping resonances, two of these definitions fall below the Chu lower bound around the frequency of operation, resulting in a fractional bandwidth larger than that predicted by the Chu limit.</div>

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Overcoming the Chu lower bound on antenna Q with highly dispersive lossy material

IET Microwaves Antennas & Propagation ◽

10.1049/iet-map.2017.0648 ◽

2018 ◽

Vol 12 (4) ◽

pp. 459-466 ◽

Cited By ~ 6

Author(s):

Arthur D. Yaghjian

Keyword(s):

Lower Bound ◽

Lossy Material

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Design of a Highly Miniaturized, Inherently Matched, Spherical Folded Dipole Antenna and Evaluation of its Quality Factor

10.36227/techrxiv.13523825 ◽

2021 ◽

Author(s):

Ashwin Iyer ◽

Sanghamitro Das

Keyword(s):

Lower Bound ◽

Quality Factor ◽

Impedance Matching ◽

Three Dimensional ◽

Dipole Antenna ◽

Fractional Bandwidth ◽

Full Wave ◽

Source Impedance ◽

Miniaturized Antenna ◽

Folded Dipole

<div>A highly miniaturized three-dimensional spherical folded dipole antenna has been reported, for which inherent impedance matching is achieved with respect to a practical source impedance by employing a simple series-LC loading combination, thereby engineering its input impedance. In order to maximize its bandwidth, the miniaturized antenna employs a bifilar spherical helix that maximizes use of the volume of the corresponding Chu sphere. Full-wave simulations show that the resulting antenna demonstrates excellent impedance matching and over 95% radiation efficiency even when miniaturized by 85% in comparison to a resonant dipole operating at the same frequency. Furthermore, various quality-factor definitions for the miniaturized spherical folded dipole antenna were estimated. It is observed that, owing to the use of proximate but non-overlapping resonances, two of these definitions fall below the Chu lower bound around the frequency of operation, resulting in a fractional bandwidth larger than that predicted by the Chu limit.</div>

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