不均質媒質による電磁波の反射に関する研究特に超高周波帯に対する積雪層の影響についての吟味
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概要
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From the point of view of classical physical theory, the reflection, scattering and diffraction of waves from objects or media have been fully understood in the sense that the underlying differential equations and boundary conditions of the relevant variables are known. It is simple, in principle, to solve these problems under the boundary conditions appiopriate to each, but, in practice this has proved to be a difficult problem even under simple and idealized conditions. Though variable methods to solve these problems strictl yor approximately and many results for them has been reported, many important and interesting subjects for practical use are remained. In this study, we investigate reflections of electromgnetic waves from the snow-covered land in order to give fundamental data for the radio wave communications using the ultra-high frequencies. In Chapter 1, we give a general analysis of the reflection of plane electrnmagnetic waves from a parallel stratified medium consisting of two slabs one of which is an inhomoheneous and the other is a homogeneous. In most cases, the snow-covered land is represented by these slabs. In Chapter 2, the electromagnetic properties of the snows and the land are considered carefully based on a number of experimental data. It is shown that there is a simple relation between the snow density and its permittivity (Cumming's relation), thus measuring the density of the snows we can get its permittivity. In Chapter 3, from a number of data of snow densities measured in our country, the changing behaviors of the permittivity of the snows are examined using Cumming's relation. From these results, it becomes clear that, in general, the snows is an inhomogeneous medium for the waves of ultra-high frequencies, that is, the permittivity of the snows must be represented by some functions of snow depth. These functional types are determined. Using these results, five model media are constructed to represent the snow-covered land. A number of data of the permittivity and density of the snows are shown in Appendix. In Chapter 4, numerical examples of reflection coefficients from the snow-covered land which is represeuted by five models are shown using the theoretical methods given in Chapter 1. and one of them is compared to experimental results, coincidence between both results is good if we assume that the land covered by snow is dry. In Chapter 5, it is shown that the theoretical treatments in this study are applicable not only the reflection phenomena of electro-magnetic wayes from the snow-covered land but also for more broad fields that elebtromagnetic or sound take part in.
- 山形大学の論文
- 1963-02-28