D.V. Fateev - Ph.D. (Phys.-Math.), Senior Research, Saratov branch, Kotel-nikov Institute of Radio Engineering, and Electronics Russian Academy of Sciences. E-mail: fateevdv@yandex.ru
V.V. Popov - Dr.Sc. (Phys.-Math.), Professor, Head of Laboratory, Saratov branch, of the Kotel-nikov Institute of Radio Engineering, and Electronics Russian Academy of Sciences
S.A. Nikitov - Dr.Sc. (Phys.-Math.), Professor, Correspondent Member of RAS, Deputy Director, Saratov branch, of the Kotel-nikov Institute of Radio Engineering, and Electronics Russian Academy of Sciences