1. A.Ya. Usikov Institute of Radiophysics and Radioelectronics of the National Academy of Sciences of Ukraine, 12
Akademik Proskura St., Kharkiv 61085, Ukraine
2. V.N. Karazin Kharkiv National University, 4 Svobody Sq., Kharkiv 61022, Ukraine
3. Department of Physics, University of North Texas, Denton, Texas 76203, USA