Estimation of intercardinal antenna pattern based on cardinal data

An interfering signal usually reaches the interfered antenna from an off bore sight direction, both in azimuth and elevation. The common methodology is to estimate the intercardinal gain G(φ,θ) as a linear combination of the cardinal patterns G(φ) and G(θ). This paper proposes a new approach based on geometrical reasoning, looking for the locus in space of pairs of angles φ and θ, having an iso-gain. The hypothesis is that these loci are ellipses drawn on a sphere. Equations for equivalent angles, φ´ or θ´ are derived. G(φ,θ) is found using the G(φ) or G(θ) pattern, at the equivalent angle. Finally, the hypothesis is compared to a numerical calculation and a good match is found.