On end-fire super directivity of arrays of two elementary dipoles and isotropic radiators

• Published in: IET microwaves, antennas & propagation antennas & propagation, 2019-11, Vol.13 (14), p.2405-2411
• Main Authors: Hazdra, Pavel, Kracek, Jan, Lonsky, Tomas
• Format: Article
• Language: English
• Subjects: antenna array; array elements; closed‐form expressions; dipole antenna arrays; directive antennas; directivity evaluation; elementary dipoles; end‐fire arrays; end‐fire superdirectivity; excitation current optimisation; excitation currents; full‐wave simulator; generalised directivity; isotropic radiators; mutual radiated powers; mutual radiation intensities; novel closed‐form expressions; optimisation; out‐of‐phase excitation; radiating source; Research Article; self‐radiated powers; self‐radiation intensities; source currents; superdirective properties
• ISSN: 1751-8725; 1751-8733; 1751-8733
• DOI: 10.1049/iet-map.2018.6013

The concept of source currents of a radiating source can be employed to express its directivity in some particular cases analytically. For an antenna array, this concept can be extended to the concept of a generalised directivity based on self- and mutual radiation intensities, self- and mutual radiated powers and excitation currents of array elements. These approaches were applied to examples of the array of two elementary dipoles and the array of two isotropic radiators. Particularly, the evaluation of the directivity of the end-fire arrays, which are of special attention due to superdirective properties, was treated. Novel closed-form expressions for the directivity of these arrays with out-of-phase excitation were derived. It was observed that the end-fire directivity can be further enhanced by optimising the excitation currents of the arrays. Their optimal phase difference and corresponding increased directivity were also found analytically. The results were validated by a full-wave simulator.