Excitation of a rectangular waveguide by pulsed electric and magnetic currents

We consider the problem of excitation of electromagnetic fields by electric and magnetic currents that are present in a rectangular waveguide. The space-time Green’s functions are obtained for a waveguide with ideally conducting walls. The primary attention is given to analysis of the energy spectrum of radiation and the influence of the finite duration of the current pulse and the finite dimensions of the conductor with the current on the above spectrum. It is shown that the influence of the above properties on the spectrum is weak at low frequencies and increases with frequency. N. I. Lobachevsky State University, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 4, pp. 456–468, April, 1998.     

Excitation of an open stripline resonator by a plane waveguide

A rigorous solution of the problem of the excitation of an open stripline resonator by a plane waveguide is obtained on the basis of an approach developed by the authors. The mechanism of the excitation of an open oscillatory system in a reflection configuration is investigated from the viewpoint of electrodynamics for various coupling regimes between the waveguide and the resonator.Institute of Radiophysics and Electronics, Academy of Sciences of Ukraine. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 37, No. 3, pp. 300–314, March, 1994.     

Excitation of a waveguide transformer

Integral immitance equations for steady-state excitation of a shielded waveguide transformer with any number of arbitrarily arranged adjoint semi-infinite waveguides are derived in the general formulation. Excitation can be carried by arbitrary inner sources (extraneous electric and magnetic currents), as well as by normal modes incident from infinity. The results are extended to the case of nonideal walls for magnetodielectric and metallic inclusions. The results give a generalization of the familiar integral impedance and admittance equations for inhomogeneous waveguides.     

Excitation of a cylindrical cavity by a helical current and an axial electron beam current

The explicit expressions (in the Vainshtein and Markov forms) are derived for the excitation of a cylindrical cavity with perfectly conducting walls and with impedance end faces. Excitation of a cylindrical cavity and a cylindrical waveguide with a preset nonuniform axial electron-beam current and a helical current with a variable pitch, which is excited by a concentrated voltage source and is loaded by a preset pointlike matched load, is considered. For the helical current, the integro-differential equation is formulated. The traveling-wave tube (TWT) is simulated in the preset beam current approximation taking into account the nonuniform winding of the spiral coil, nonuniform electron beam, and losses.     

Excitation of spin waves by an electric current

The excitation of spin waves in an unbounded ferromagnetic film by a direct spin-polarized current distributed over a small area is treated macroscopically. The derived critical threshold current for excitation has two additive terms: The first arises from radiation of spin waves and is constant. The second arises from local viscous dissipation and varies in proportion to damping coefficient, external field, and area. An application of these predictions modifies the existing interpretation of experiments by Tsoi and collaborators employing currents flowing through point contacts.     

Excitation of microwave by an annular electron beam in a plasma-filled dielectric lined waveguide

An axial relativistic electron beam passing through a slow wave structure is unstable to an electromagnetic perturbation whose phase velocity equals the velocity of the beam. This phenomenon of Cherenkov emission is the basis of all traveling wave tubes. In this paper an excitation of Cherenkov radiation by a thin annular relativistic electron beam in a plasma-filled dielectric-lined waveguide is analysed by use of the self-consistent linear theory. The effect of the thin annular electron beam on the beam-wave interaction is completely described by a jump condition. The dispersion equation and the simultaneous condition of the beam-wave interaction are derived. Finally, the growth rate of the wave is obtained, and the effect of the background plasma density and the electron beam radius on the growth rate of the wave are presented.This work is supported by National Natural Science Foundation of China.