PULSE SIGNALS IN OPEN CIRCULAR DIELECTRIC WAVEGUIDE

Abstract

PULSE SIGNALS IN OPEN CIRCULAR DIELECTRICWAVEGUIDEM. Legenkiy and A. ButrymDepartment of Theoretical RadiophysicsKarazin Kharkiv National University4 Svobody Square, Kharkiv 61077, UkraineAbstract|Excitation and propagation of a pulse electromagneticwave in an open circular dielectric waveguide is considered. Partition ofthe pulse fleld into radiated wave, surface wave, and guided wave hasbeen revealed and the corresponding physical efiects are interpreteddirectly in the time domain. Namely it was shown that there is aprecursor at the rod axis that propagates with speed of light in freespace. It originates from the pulse surface wave that propagates alongthe rod surface and radiates into the rod in a Cherenkov like manner.1. INTRODUCTIONOne of the main trends in communications recently consists inincreasing channel capacity by exploiting ultrawideband short pulses.Among transmission lines that are of high interest in communicationsare optical flbers (dielectric waveguides). Propagation of ultrashortelectromagnetic pulses in such lines has not been studied su–cientlyyet. So it is of interest to consider physical processes that occurwith excitation and propagation of pulse signals in open dielectricwaveguides. This problem is also met in analysis of pulse radiationfrom a rod antenna.Harmonic wave propagation in dielectric waveguides is wellstudied in the Frequency Domain (FD) [1]. In this case the soughtfleld in the structure is presented as a set of uncoupled modes. Thereare guided wave modes that have fleld localized within the rod, thespectrum being discrete. These modes are used for transmittinginformation. In describing flelds near the sources one also needs to