Atmospheric deflection of radar beams and evaluation of eclipse zones

This paper investigates the deflection of an EM wave emitted from an airborne radar due to the variance of refractive index (n) with height (h) in the atmosphere. Also, the insertion loss of the atmosphere due to refraction, resulting from the cumulative reflection coefficient, is discussed. The effect of both standard and non-standard refractive index changes with height (n-profiles) is considered, with particular interest in the effect of a generic elevated superstandard layer with an elevated duct. It is verified that these non-standard n-profiles lead to 'eclipse zones', where the rays cannot propagate. The ray path deflection problem is solved by dividing the atmosphere into several discrete layers, evaluating the refractive index within these layers, and then using Snell's law to obtain the angles of refraction for the ray at each layer boundary. The attenuation problem is solved by applying a transmission line analogue to the ray path through the atmosphere.