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

<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 spherical helix structure as the folded arm that occupies the full volume of the corresponding Chu sphere. A bifilar (two folded arms) and a quadrifilar (four folded arms) helix loaded folded dipole antenna are designed, and full-wave simulations show that both the resulting antennas demonstrate excellent impedance matching when miniaturized by 85% in comparison to a resonant dipole operating at the same frequency. Despite the high degree of miniaturization, the resulting radiation efficiencies for the bifilar and quadrifilar antennas are found to be 87.1% and 90.6%, respectively. Furthermore, various quality-factor definitions are explored for the quadrifilar antenna, and it is observed that the resulting quality factor is around 1.83 (1.22) times that predicted by the Chu (Thal) lower bound.</div>

SIMULATION OF A FLEXIBLE LINEAR GRAPHENE ANTENNA ARRAY ON A PAPER SUBSTRATE

The article presents an analysis of flexible graphene antenna arrays, which has shown the promise of using a folded dipole antenna as an element of such array. The structure of the flexible folded dipole operating at a frequency of 5,8 GHz on a photo-paper substrate is considered. Simulation yields a gain of 2,53 dBi with a final efficiency of 75% and | S 11| -31,82 dB. The influence of bending on the final shape of the radiation pattern is considered, as well as the value and position of the minimum of the | S 11|. The gain of a linear three-element graphene flexible antenna array based on a folded flexible dipole is 5,78 dBi.

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

<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>

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

<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>