Refracted propagation effects for airborne radar

In this paper, we present results on the consequences of refracted propagation for airborne radar mathematical modeling. That is, given an atmosphere of varying refractive index, the path of EM radiation is curved in general; we look at the effects this has upon radar performance, and at how such effects are to be modeled. An effective Earth radius factor k is derived that is valid for all airborne radar altitudes, and which reduces to the familiar k=4/3 value at low altitudes. Horizon ranges are calculated numerically and analytically. Radius of curvature is determined, and the consequences of curved paths for elevation beamshape loss and range gating is discussed. Loss calculations are presented, and modeling implementation considerations are summarized.