Effects of metal fences on the scan performance of an infinite dipole array

A theoretical method is presented to investigate the scan characteristics of a dipole array in the presence of thin metal fences along the H-plane. The basic idea of the analysis is to determine the current distribution on the dipole which interacts with the metal fence in the unit cell, so that the active impedance of the element can be computed. This was accomplished by using the moment method and imposing the boundary conditions on the tangential electric fields along the dipole and the metal fence. Since the scan performance in the H-plane is not affected by the fences, the discussion is concentrated on the E-plane behavior. It was found that for a given element spacing and dipole geometry there is an optimum fence height at which the E-plane performance can be most improved. For a typical dipole array geometry the optimum fence height is about 0.4 λ. It was thought that when the fences are to high and the beam is scanned too far from broadside, transverse magnetic (TM) surface waves propagating in the E-plane direction near the corrugated plane would be excited. However, no such sensitive cases were encountered in the study