Volume 61, Nº 5 (2016)

General properties of eigenmodes in periodic arrays of coupled waveguides are considered. The Floquet channel model is used to analyze arrays operating in the quasi-periodic mode. Relationships for the orthogonality of different types of eigenmodes are obtained on the basis of the Lorentz lemma and the active power theorem. The problem of excitation of array eigenmodes by given currents is solved. The relation between two representations of the array field, by means of the eigenmode expansion and in the form of the Fourier integral, is shown by the example of an array of coupled slot lines.

A rigorous and an approximate method are applied to solve the problem of diffraction of electromagnetic waves of the optical range from a 2D grating made of rectangular metal strips. The rigorous method is based on the numerical-analytical method of the solution of a volume integro-differential equation (VIDE). In the second method, the approximate boundary conditions (ABCs) for a thin dielectric layer are used. The correctness of the ABC method applied for determining the basic physical regularities is justified. More accurate ABCs and the notion of effective dimensions of strips are introduced.

The problem of determination of the equivalent surface impedance of a rectangular groove is considered. The solution is obtained by the integral equations method. The Krylov–Bogoliubov method is used to solve integral equations numerically. The obtained dependence of the impedance value on the groove depth is compared to the dependence calculated using an approximate formula for different groove widths. The limits of applicability of the approximate formula are determined.

Variations in some parameters of microwave electronic devices under the action of technological irregularities are approximately estimated. The original electromagnetic problem with random boundary conditions is reduced to calculation of interaction between the electron flow and the electromagnetic field of the slow-wave structure with parameters gradually varying along the flow (for this purpose, an irregularity displacement theorem is proved). The use of the Cauchy distribution, which is similar to the normal distribution of irregularities over the cells reduces calculation to simple estimation formulas. The calculation procedure is illustrated by the example of estimations for a travelling-wave tube and a backward-wave tube with a flat comb-type slow-wave structure.

A numerical model, as well as a simpler analytical one, which describe heat accumulation in microwave semiconductor devices exposed to high-power electric-pulse trains, are constructed. Conditions are estabtished under which heat is accumulated with each subsequent pulse up to the onset of a catastrophic failure caused by the device burnout. It demonstrated that short-pulse trains with a small pulse period-topulse duration ratio are most dangerous.

An experimental setup for investigating the immunity of computer equipment to the power-line electromagnetic interference has been developed. The results of quantitative investigations of the performance of the computer equipment subjected to the action of nanosecond and microsecond electromagnetic pulses propagated through the power line as well as the results of investigations of the efficiency of external devices for protecting the computer equipment from the action of electromagnetic pulses propagated through the power line are presented.