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Cylindrical Antennas with Rigorous Allowance for the Ground Influence in the VLF-Region


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This document treats some characteristic problems of emission and transmission of very low frequency (VLF) electromagnetic waves. A calculation of the ground reaction on the antenna current is made for the case of a long wire antenna positioned horizontally above the earth and vertically within the earth. Wave propagation with a locally perturbed ionosphere is investigated. Here, a rectangular lowering or heightening of the ionosphere is assumed so that a perturbing edge separates the perturbed from the unperturbed region of the ionosphere. A wave front impinging parallel and at an oblique incidence to the perturbing edge is considered. Explicit calculations of reaction current, with an assumed high ground conductivity, yield graphs showing the dependence of reaction current on frequency and distance above or below the ground. Upon establishment of a rigorous solution for parallel incidence of an impinging wave on a slightly perturbed ionosphere, an approximate solution is presented with satisfactory results. The perturbed field is obtained with several, mathematically different, techniques (iteration and S-matrix). It is shown that the oblique incidence of a plane wave not only splits it into single modes upon passing the perturbing edge, but that there is a further splitting of directions. The respective amplitudes and deviation angles of the modes are calculated.



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