Results of the Researches of Attenuation of the Energy of Electromagnetic Waves by Optically Non-Transparent Barriers

Abstract

The results of experimental researches of losses of electromagnetic energy in the decimeter bandwidth after the waves propagation through the elements of building structures are examined from the point of view of the basic requirements set to the radar characteristics in terms of detection of people behind the optically non- transparent obstacles. The samples of building structures and construction materials representing the most probable options of obstacles during the man-caused disasters are selected as objects of research. Dependences of radio waves attenuation upon the frequency and polarization are investigated. Possibility of reception of the reflected electromagnetic signals in the decimeter bandwidth from moving living beings behind the concrete and armored concrete ceilings and walls is considered. The requirements set to the conditions of experiments and methodology of their performing are discussed. Authenticity of results is substantiated. One of the most important problems arising during the development of radars for detection of people behind the optically non-transparent obstacles lies in adoption of the optimal operating band. It is evident that solving a target detection problem is possible only in the case when the radio signal after propagation through all of the obstacles in both directions (from the radar to the target and backwards) will be sufficient in terms of its level to detect a human being with a great deal of acceptable probability. The difficulty of theoretical defining of losses along the path of radio waves propagation even at their propagation through the atmosphere, clouds, fog, rain, snow, hail, is mentioned in the papers [1,2]. In the considered by us cases we mean using of radars to save the life of the people blocked by debris of ruined buildings, layers of the 1033 ISSN 0040-2508 © 2008 Begell House, Inc. * Originally published in Radiophysics and Electronics, Vol. 12, No 2, 2007, pp. 426-434. I.A. VYAZMITINOV, YE.I. MYROSHNYCHENKO, AND O.V. SYTNIK ground or other loose materials etc. At theoretical estimation of losses at the radio wave propagation through the above obstacles there occur such difficulties that the estimate turns out to be either rough or the calculation appears very labor-intensive [3,4]. This is caused also by the fact that on their way to the target the radio waves are subject not only to the absorption by but also to the reflection from various heterogeneities. In most cases with the accuracy, which is sufficient for practical purposes, the depth of radio oscillation penetration into the homogeneous medium can be estimated upon the following approximated formula [5-8]