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(/spl phi/,/spl theta/) as a linear combination of the cardinal patterns G(/spl phi/) and G(/spl theta/). This paper proposes a new approach based on geometrical reasoning, looking for the locus in space of pairs of angles /spl phi/ and /spl theta/, having an iso-gain. The hypothesis is that these loci are ellipses drawn on a sphere. Equations for equivalent angles, /spl phi/' or /spl theta/' are derived. G(/spl phi/,/spl theta/) is found using the G(/spl phi/) or G(/spl theta/) pattern, at the equivalent angle. Finally, the hypothesis is compared to a numerical calculation and a good match is found.