S. V. Turygin - Engineer, Department of Biomedical technique of Vologda state technical university
V. A. Yatskevich - Dr.Sci. (Eng.), Professor, Head of Microwave Electromagnetic Research Laboratory of Vologda state pedagogic university. E-mail: vayatskevich@yandex.ru

A common drawback of microwave hyperthermia devices is the following. Electromagnetic wave propagating in the human body is strongly attenuated, so transmission power have be increased to heat the internal organs. This leads to an undesirable overheating of the skin and subcutaneous tissues. Usually to reduce overheating a system of skin water cooling is used, which makes difficult to carry out medical procedures. The purpose of this article is to offer a microwave radiator which provides reduced skin zone heating and subcutaneous tissue heating at a constant level of heating of internal organs. The emitter consists of two symmetric dipoles, connected with wire crossed lines, and a screen with an elliptical cross-section. Dimensions of elements are selected to produce an interference minimum of EM field in skin zone. Simulation was done at a frequency of 915 MHz using a computer software designed to solve the boundary electromagnetic problem by a finite integrals technique. The elliptical cylinder whose cross-section consists of three layers, corresponding to the skin, fat layer and the muscle tissue, was used representing human body. The calculated distribution of the absorbed power density indicates that the proposed emitter can significantly reduce heating of the skin and form a region of intense heat in the muscle tissue.