Hf radio channel modeling by a waveguide approach

We present a modified method of HF radio channel modeling based on a waveguide approach. The waveguide approach represents the electromagnetic field of radiation inside the Earth-ionosphere waveguide as an eigenfunction series of a radial boundary problem with impedance conditions on the Earth surface and radiation conditions at infinity. The transfer function of the radio channel is represented as a series of products of angular-operator Green functions, excitation coefficients, and coefficients for receiving individual normal modes. We have obtained a solution of the boundary value problem of determining the eigenfunc- tions and eigenvalues of the radial operator. The solution can be applied to the frequency range below the ionospheric F-layer critical frequency. We examine algorithms for calculating distance-frequency, frequencyangular, and amplitude characteristics of signals by analyzing and numerically summarizing the series in terms of strongly damped normal modes.