  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.
