A.P. Trifonov - Dr. Sc. (Eng.), Honored Scientist of RF, Professor, Head of Department of Radiophysics, Voronezh State University. E-mail: trifonov@phys.vsu.ru Yu.E. Korchagin - Dr. Sc. (Phys.-Math.), Associate Professor, Department of Radiophysics, Voronezh State University. E-mail: korchagin@phys.vsu.ru