Том 63, № 7 (2018)

An analytical solution to the problem of ultrashort radio pulse propagation in the gas medium with two isolated spectral lines, which is obtained without Fourier integral calculations and is not restricted by the path length or the selection of the a priori time dependence of the field strength of an emitted pulse, is presented. As applied to a ground path, this solution was used to consider possible behavior and features characterizing the distortions of a sinusoidal train and a rectangular quasi-monochromatic pulse, the spectra of which belong to the atmospheric transparency window restricted by frequencies of 326.4 and 380.1 GHz. The dependences between the integral characteristic of pulses and the carrier-frequency position with respect to boundary frequencies are analyzed.

The possibility of using modern program complexes for the analysis of electromagnetic fields in a double-mirror open resonator (OR) with a focusing mirror of a complex form including an OR of an orotron in the submillimeter wavelength range is considered. The values of resonance frequencies and the distribution of the fields of the fundamental oscillation type in the OR with a focusing five-focus spherical mirror are obtained with the use of the CST Studio Suite and HFSS Ansoft program complexes. In addition, more accurate values of the Q-factor and stored energy in such ORs with the single- and double-row periodic structures on a plane mirror are obtained. Therefore, the values of the electron efficiency of an orotron can be calculated more reliably.

The spectrum of symmetric modes forming a specified distribution of the radiation field is calculated using solution to the self-consistent problem of radiation from the end of a circular dielectric waveguide. The self-consistent problem is reduced to solution of a system of integral equations. In the case of the synthesis of the source function in the space of eigenfunctions of the boundary value problem for a circular dielectric waveguide, these equations are the Fredholm integral equations of the first kind.

The paper presents a theory of radiation by an accelerated linear laser cavity at imaginary eigenfrequencies. Expressions for the phase, frequency, and allowed directions of radiation are given. It is found that, in a rigid cavity moving with a constant acceleration together with a photodetector, two groups of frequencies with four different complex arguments are radiated. A relation between the earlier introduced radiation vector and the wave vector is established. It is shown that the radiation vector, which determines the eigenvalues of the spatial problem, is a multiple of the wave vector if boundary conditions are imposed along only one coordinate, when the side walls of the cavity with a plane front are located at infinity.

The paper presents a numerical and numerico–analytical models of the radiation of an infinite cophased antenna array of TEM horns, including the model with metallization of the space between neighboring (in the E-plane) horns. The numerical model is based on the finite-element method, and the numerical model, on the integral equation, Galerkin, scattering matrix, and coupled-wave methods. The numericoanalytical modeling has shown that, in such arrays, an anomalously high backward radiation is observed and that the proposed numerico–analytical model can describe this effect both qualitatively and quantitatively.

Voltage ripple of electrode sensor that moves relative to electrolyte (flow noise) is interpreted in agreement with experimental data using variations in the adsorption rate of oxygen on the electrode surface upon variations in the thickness of the diffusion layer. A relationship of electrode potential and flow velocity jumps is derived. It is shown that the electrode voltage ripple is proportional to the pulsation of the liquid flow velocity and is inertial with respect to such a pulsation with a time constant of several milliseconds. It is also shown that the sensor sensitivity to velocity pulsations exponentially decreases with a time constant of several hours. The dependences of the ripple amplitude on the pulsation frequency of the velocity, electrolyte concentration, and storage time of electrodes in electrolyte that are obtained using the above relationship are proven in experiments.

An algorithm for robust frequency estimation in a channel with additive white Gaussian noise and pulse interference is proposed. The algorithm involves iterative elimination of pulse interferences and subsequent calculation of the maximum likelihood estimate. It is demonstrated that the proposed filter-cleaner differs from the well-known Martin–Thomson filter in the functional dependence of adaptive coefficients on the estimates of parameters of distributions of the linear prediction error and the amplitude envelope of the signal. The results of mathematical modeling and numerical estimation of the threshold point of the method (0.49) are presented.

A 2D problem of the diffraction of plane electromagnetic wave by a graphene ribbon on a finitesize dielectric substrate is considered for the TM polarization. Rigorous numerical methods are used to calculate the scattering cross sections in the terahertz frequency range. It is shown that multipole resonances vanish in the scattering spectrum in the presence of a small substrate that represents a thin dielectric film.

Suppression of cross coupling between dielectric plasmon waveguides by inserting an additional waveguide between two main waveguides has been demonstrated. It has been found that the cross-sectional dimensions of the system can be less than two microns, i.e., several hundreds of times smaller than the cross-sectional dimensions of a system made with the use of a dielectric fiber. It has been determined that modes propagating in these waveguides are the sum of one of the symmetric modes and one antisymmetric mode of the coupled system, and the cross coupling is suppressed by matching the wave numbers of these modes. Analytical results are confirmed by numerical simulation.

(m–i–p)-Structures with high-resistance epitaxial i-layers are fabricated on heavily doped p⁺-type substrates with platinum contacts. The structures are studied using several methods: optical and electron microscopy and luminescence, and electrophysical (C–V and I–V characteristics) methods and tested as detectors of ionizing radiation. It is shown that the (m–i–p)-structures are promising for development of several electronic devices (high-voltage diodes, detectors of ionizing radiation, and photovoltaic devices).