Vol 68, No 8 (2023)

The results of the analysis of the energy consumption of the transmitting active phased antenna array (APAA) of a spacecraft of the low-orbit communication system (with broadband access or with direct access to cellular subscribers) have been presented. It has been shown that in order to reduce energy consumption by switching on (off) the emitters, depending on the beam deflection angle from the nadir, it is possible to achieve a significant reduction in the heat release of the spacecraft’s APAA. But this solution is feasible only if the APAA forms one “jumping” beam.

The problem of the influence of the rocket engine plume (REP) plasma on the radiation pattern (RP) of the onboard third stage antennas launch vehicle. The possibility of using the method of the impedance analog of the Sestroretskii electromagnetic space for solving this problem is shown. The distribution pattern of the plasma frequency in the REP is presented. The distribution patterns of the amplitude and phase of the magnetic field in the region under study are obtained. The RPs of the antenna system are presented, showing a significant shift in the direction of the main lobe and a change in its shape.

Algorithmic solutions have been developed to assess the quality of communication with an unmanned aerial vehicle. The quality of communication is determined by the probability of a symbol error at the input of an                                        error-correcting encoder, the a priori calculation of which is performed in the approximation of Rice’s communication channel model. The main attention in the solution is given to the determination of attenuation due to the combined influence of the terrain and tropospheric refraction on the energy parameters of the line ground communication point–unmanned aerial vehicle. The attenuation was calculated by jointly solving a pair of parabolic equations formed from the two-dimensional Helmholtz equation in narrow- and wide-angle approximations by the pseudospectral method of separating the steps of a pair of parabolic equations. In the features of the main stages of the algorithmic implementation of the developed solution are highlighted, and its performance is tested on specific test examples.

An algorithm for estimating the spectral correlation function of cyclostationary random processes on the basis of their finite-time realization is proposed. The main algorithm steps are described and the main operations performed at each of them are formalized. The presented estimates of the spectral correlation function in the presence of a correlated stationary noise overlapping the analyzed cyclostationary random process in the frequency domain confirm the efficiency of the algorithm with a low signal-to-noise ratio. The number of required computational operations and the amount of computer memory required for storing intermediate results are estimated.

Applications of the two-dimensional full-wave electromagnetic code Tamic Analyzer, developed by B.V. Sestroretskii to study the limiting possibilities of diagnostics of reflectometry in tokamak plasma. It is shown that by comparing experimental reflectometry data with calculations using this code, it is possible to determine the structure of density fluctuations in a tokamak, but the experimental radial correlation lengths can be significantly overestimated. Simulation using the Taimic Anylyser code made it possible to determine the limiting level of density fluctuations at which it is possible to measure the plasma density profile and observe Alfven fluctuations in the International Experimental Thermonuclear Reactor of the tokamak type (ITER) under construction. Possible ways to increase the speed and counting field of the code are considered.

A structure of a radio absorber (RA) with a high stability of resonance frequency based on a resistive film with a sheet resistance of 120 Ω/sq and an artificial magnetic conductor in a pair of capacitive gratings on a dielectric layer with a high permittivity (epsilon_1 >>1) metallized on the opposite side is proposed. The results of numerical calculations of the frequency–angular dependences of the RA reflection coefficient confirm preliminary estimates obtained from analytical expressions. For example, at epsilon_1 = 20  , the shift of the resonance frequency is no greater than 2% at angles of incidence of phi=0^o...60^o , and the bandwidth-to-thickness ratio is 4.29 at phi=0.

A conservative model is proposed for a weakly conductive material medium with changing thermodynamic characteristics during the propagation of a pulse in it. Equations are obtained that describe the change in the shape of the profile of a video pulse propagating in a medium, as well as in nonlinear transmission lines with a temperature dependence of the permittivity. It is shown that if the temperature coefficient of the permittivity is negative, then the peak power of the pulse can increase with time; otherwise, the temperature dependence of the permittivity leads to an increase in attenuation.

The field dependences of the electrical conductivity of Pt/diamond-like carbon (DLC)/Pt structures based on thin layers of high-resistivity DLC are studied. It is shown that the nonohmic behavior of theconductance of structures is described by the Frenkel–Poole formula and is related to correlated distribution of charges under conditions of their percolation hopping transport between low-resistance DLC regions.