A.P. Trifonov - Dr. Sc. (Eng.), 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 K.D. Titov - Post-graduate Student, Department of Radiophysics, Voronezh State University. E-mail: titovkd@gmail.com