I.A. Nakrap – Ph.D.(Phys.-Math.), Associate Professor, 

Department of Radiotechnique and Electrodynamics, Saratov State University named after N.G. Chernyshevsky E-mail: nakrapia@info.sgu.ru

A.N. Savin – Ph.D.(Phys.-Math.), Leading Research Scientist, 

JSC «RPC «Istok» named after Shokin» (Fryazino)

E-mail: savinan01@yandex.ru