Superdirective Arrays with Finite-Length Dipoles: Modeling and New Perspectives

TL;DR

This paper models dense linear arrays of finite-length dipoles to explore superdirectivity, revealing that high gain with efficiency is achievable with optimal design and specific dipole lengths.

Contribution

It introduces a sinusoidal current distribution model for finite-length dipoles and analyzes superdirectivity in dense arrays, combining theory with simulations.

Findings

Supergain is achievable with high efficiency.

Optimal array design involves conjugate power matching.

High radiation efficiency occurs when dipoles are not too short or thin.

Abstract

Dense arrays can facilitate the integration of multiple antennas into finite volumes. In addition to the compact size, sub-wavelength spacing enables superdirectivity for endfire operation, a phenomenon that has been mainly studied for isotropic and infinitesimal radiators. In this work, we focus on linear dipoles of arbitrary yet finite length. Specifically, we first introduce an array model that accounts for the sinusoidal current distribution (SCD) on very thin dipoles. Based on the SCD, the loss resistance of each dipole antenna is precisely determined. Capitalizing on the derived model, we next investigate the maximum achievable rate under a fixed power constraint. The optimal design entails conjugate power matching along with maximizing the array gain. Our theoretical analysis is corroborated by the method of moments under the thin-wire approximation, as well as by full-wave simulations. Numerical results showcase that a super-gain is attainable with high radiation efficiency when the dipole antennas are not too short and thin.