Analysis of microwave ducting in an inhomogeneous troposphere

Abstract

Theory for the transmission of electromagnetic waves in a non-uniform troposphere is presented. The atmospheric refractive index is allowed to vary both with height and range. The formulation is facilitated by the fact that the field within a piecewise (laterally) uniform section can be represented by a discrete sum of modes that are orthogonal in the transverse plane. Using the appropriate radial wave functions, mode conversion at a junction between two laterally uniform sections is considered. The analysis is then extended to multi-section structures. A few typical profiles of refractive index are examined numerically for both uniform and non-uniform models. One of the important findings is that the lateral non-uniformities in an elevated duct will enhance the overall transmission for ground-based transmitting and receiving antennas.