Quasi-harmonic oscillations in a nonlinear transmission line, resulting from cherenkov synchronism

• Main Authors: Karelin, S.Y., Krasovitsky, V.B., Magda, I.I., Mukhin, V.S., Sinitsin, V.G.
• Format: Article
• Language: English
• Published: Національний науковий центр «Харківський фізико-технічний інститут» НАН України 2019
• Series: Вопросы атомной науки и техники
• Subjects: Nonlinear processes
• Online Access: http://dspace.nbuv.gov.ua/handle/123456789/195168

Experimental data and results of numerical modeling are presented, concerning excitation of microwave oscillations by a wave of pulsed ‘dc’ current (eventually, a shock wave) traveling through a radially non-uniform coaxial guiding structure. Similar experiments with ‘standard’ structures that involve a nonlinear dielectric insert (ferrite) in the coax and another dielectric, characterized by a smaller dielectric constant, result in appearance of a short radiofrequency pulse, in the form of decaying sinusoidal voltage at the line’s output. The decay is shown to be associated with a lack of velocity synchronism between the principal ‘quasi-TEM’ wave mode in the system and the slow Emode excited by the electromagnetic shock. Numerical experiments within 3-D models have demonstrated possibilities for obtaining radio pulses of various lengths, involving oscillations of a stable frequency and nearly constant amplitude – provided that Cherenkov-type synchronism were satisfied, owing to slowing down of the faster ‘quasiTEM’ mode. To cut its speed down two methods can be suggested, (i) using a dielectric material with a high value of the dielectric permittivity, and (ii) introducing a periodic slow-wave structure whose period would be smaller than the wavelength of the oscillations considered.