On the End-Fire (Super) Directivity of an Array of Two Elementary Dipoles

TL;DR

This paper analytically investigates the superdirective end-fire directivity of a two-element elementary dipole array, deriving optimal excitation conditions and validating results with simulations.

Contribution

It provides a closed-form expression for the array's directivity and analytically determines optimal excitation parameters for superdirective performance.

Findings

End-fire directivity can be significantly enhanced through optimal excitation.

Closed-form expression for directivity of out-of-phase dipole array is derived.

Simulation results confirm analytical predictions.

Abstract

The concept of source currents of a radiating source can be employed to express directivity in some particular cases analytically. For an antenna array, this concept can be combined with concepts of mutual radiation intensity and the mutual power of array elements. Using these approaches, we treat the evaluation of the directivity for an elementary dipole, and its end-fire array, which is of special attention due to superdirective properties. A closed form expression for the directivity of this array with out-of-phase excitation is derived. It is observed that end-fire directivity can be further enhanced by optimizing the excitation currents of the array. Their optimal relative phase and corresponding increased directivity are also found analytically. The results are validated by a full-wave simulator.