Metallic Wire Array as Low-Effective Index of Refraction Medium for Directive Antenna Application

Two-dimensional (2-D) metallic wire arrays are studied as effective media with an index of refraction less than unity $(n_{rm eff}?1)$. The effective medium parameters (permittivity $varepsilon_{rm eff}$, permeability $mu_{rm eff}$ and $n_{rm eff}$) of a wire array are extracted from the finite-element simulated scattering parameters and verified through a 2-D electromagnetic band gap (EBG) structure case study. A simple design methodology for directive monopole antennas is introduced by embedding a monopole within a metallic wire array with $n_{rm eff}?1$ at the antenna operating frequencies. The narrow beam effect of the monopole antenna is demonstrated in both simulation and experiment at X-band (8–12 GHz). Measured antenna properties including reflection coefficient and radiation patterns are in good agreement with simulation results. Parametric studies of the antenna system are performed. The physical principles and interpretations of the directive monopole antenna embedded in the wire array medium are also discussed.