Innovations in Applied Physics

Results of development of the nonlinear theory of relativistic TWT and BWO on irregular hollow waveguides with cathode filter-modulator with the account as propagating, and beyond cut-off waves are given. The results of optimization on efficiency of variants relativistic Cherenkov oscillators are given. The rigorous theory of excitation of an irregular electrodynamic system is used to solve the problem of determining the profile of output horn of Cherenkov oscillators that provides a required mode structure at the output and an optimum directivity pattern.

The method of combined volume and surface integral equations has been proposed for simulation of radio-frequency identification tags. Their approximate models have been built to calculate the input impedance and the radiation pattern. Various planar and nonplanar tag’s structures have been considered and their parameters have been obtained.
 

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The results of an experimental study the dispersion characteristics and field distribution of main and higher order modes of multirow interdigital slow wave structures with their resized are presented. The ways of increasing the frequency separation of main and higher order modes and the working excitation band of the main mode are offered.  Investigation the forced oscillations of the multirow interdigital slow wave structure with exponential H-waveguide power ports has shown the possibility of a single-mode excitation in a wide bandwidth.

The estimation of optimal parameters with the analytical model regarding nonlinear electron motion dynamics is fulfilled for the submillimeter-wave M-type oscillator tor operating on frequency about 0.33 THz with anode voltage 13 кV and magnetic field 0.7 Т. Revealing from this model, the magnetron interaction space geometry providing the effective electron interaction with a high-frequency field on (+1) spatial harmonic of π-mode oscillations is proposed for the drift-orbital resonance regime.

The study of the microwave generation regimes with intense higher harmonics taking place in a high-power vircator consisting of a relativistic electron beam with a virtual cathode has been made. The characteristics of these regimes, in particular, the typical spectra and their variations with the change of the system parameters (beam current, the induction of external magnetic field) as well as physical processes occurring in the system have been analyzed by means of 3D electromagnetic simulation.

For masers on cyclotron resonance it is researched a possibility of induced scattering of the opposite feedback wave on relativistic electron beam to the following wave of higher frequency. This effect can be used for powerful TGz-radiation receipt in a generator of millimeter range of wavelengths.

Numerical model of long fiber Raman laser is proposed. The model based on the equations, describing the propagation of pump and Stokes waves, linear coupling of oppositely running waves due to scattering and its nonlinear interaction. The derivation of equations for slowly varying pulse envelopes uses the field decomposition in terms of spatial harmonics rather then commonly used temporal harmonics, which allows to avoid the two­point boundary conditions, and to employ the numerical scheme of Courant–Isaakson–Rees.

It was stated in the paper the mathematical model and its numerical realization for the investigation of wideband chaotic oscillations and of physical processes in the electron beams with virtual cathode at the generators with electron feedback. Also it was briefly described the developed program package for the modeling of non­stationary nonlinear physical processes at the electron generators with virtual cathode and for calculating of output characteristics of devices.

The modes of the planar dielectric waveguide made from nonlinear metamaterials with both negative permittivity and permeability are investigated. The dependencies of the propagation coefficients of the guided mode on the transmitted power are studied. The fields distributions are calculated for the systems with variable permittivity and permeability profiles. It is shown that in such systems a drastic increase in the field magnitudes may occur.

The work studies the effects of temperature on drift velocity of the electrons in semiconductor superlattices in electric and tilted magnetic fields. It is shown that a thermal distribution of the electrons can counter­intuitively enhance the phenomena related to resonances between the Bloch and the cyclotron frequencies of electron motion in superlattices. In particular, the increase of temperature leads to more prominent resonant maxima in the dependence of drift velocity of electrons on the strength of an electric field.