Abstract-An E-wave excites longitudinal conductivity currents in a waveguide filled with lossy medium. Total flow of this current through a cross-section is nonzero for odd E-modes; it means that some charge is transported by the pulse along the waveguide. This phenomenon is considered in the paper using analytical approach based on mode expansion of the fields in Time Domain (known as Mode Basis Method) and using Finite Difference in Time Domain method (FDTD). Volume conductivity charges being moved by the pulse wave are determined. In order to set the problem as much physically as possible we consider diffraction of a pulse E-wave on the boundary between a hollow waveguide and a waveguide with conductive medium. Behavior of the transient fields and surface charges at the interface are also examined. It is shown that an incident pulse wave excites a surface wave at the interface that results in transversal resonance with relaxation time much greater than that of the conductive medium. Characteristics of the travelling charge pulse wave are studied based on the obtained closed-form solution.

A new method is presented for analysis of transient electromagnetic fields in regular structures with abrupt discontinuities. The method is based on mode expansion of the fields in the Time Domain. The modes propagate independently in the regular parts of the structure and are coupled at the discontinuity. The main idea consists in solving 1D FDTD equations for each independent mode channel in the regular waveguides and using mode-matching at the junction cross-section in order to relate the mode amplitudes in all the channels at the same time instant via imposing boundary conditions. As examples the problems of pulse signal diffraction at a step discontinuity in a parallel-plate waveguide, diffraction at a junction of circular and coaxial waveguides, and pulse radiation of a bi-conical antenna are considered. The latter problem is treated as a junction of two conical lines (one of which is the free space) that are regular in spherical coordinates.

The paper discusses radar detectability of an onground object. The main question is how to estimate the effectiveness of some measures on detectability reduction, such as applying radio absorbing materials to parts of the object. The cloaking effectiveness measure is expressed as a quantity that is independent of the radar characteristics, except for polarization, wavelength, and the observation aspects range.

Excitation and propagation of a pulse electromagnetic wave in an open circular dielectric waveguide is considered. Partition of the pulse field into radiated wave, surface wave, and guided wave has been revealed and the corresponding physical effects are interpreted directly in the time domain. Namely it was shown that there is a precursor at the rod axis that propagates with speed of light in free space. It originates from the pulse surface wave that propagates along the rod surface and radiates into the rod in a Cherenkov like manner.

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