Radio wave propagation over earth : field calculations and an implementation of the roughness effect

Dawe, Barry John (1988) Radio wave propagation over earth : field calculations and an implementation of the roughness effect. Masters thesis, Memorial University of Newfoundland.

[English] PDF (Migrated (PDF/A Conversion) from original format: (application/pdf)) - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (20MB) [English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. (Original Version)

Abstract

Computer programs are developed to calculate radio propagation losses over the ocean surface. The effects of the ocean surface roughness are evaluated through numerical implementations of modified surface impedance expressions. The surface roughness is expressed in terms of standard oceanographic models for the directional ocean wave height spectral density. The modified surface impedance may be used with either a planar earth propagation model, for short propagation distances, or a spherical earth propagation model for long propagation distances. -- The planar earth solution for the electric field distant from the source, is derived using a spatial decomposition method and expressed in the form of the spatial Fourier transform of the electric field. No assumed boundary conditions are used in the derivation; the method supplies its own boundary conditions. As well, the surface impedance and the choice of source remains arbitrary. For a highly conductive surface, such as the ocean surface and an elementary vertical electric dipole source, the expressions reduce to the classical planar earth results. -- For long propagation distances, the effects of radio wave diffraction around the curvature of the earth’s surface are significant. A computer program has been written using modern compact computer code which implements the classical residue series results for ground wave spherical earth propagation. The program accounts for rough surface effects using an implementation of the modified surface impedance for a rough ocean surface. Transmission loss results for a variety of frequencies in the MF and HF bands and a variety of sea states are presented which compare favourably to previous results.

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