Vol 70, No 3 (2025)

A review of achievements in the field of research of electromagnetic waves with spiral phase front and their applications is presented. Known methods of radiation and receiving of such waves are considered, as well as their application to increase the efficiency of frequency spectrum use in radio communication systems due to simultaneous transmission of signals on several vortex modes with different angular indices, to improve the performance of radar systems with synthetic aperture by obtaining additional information, methods of reducing backscattering of radar objects. The ways of further research are discussed.

The problem of determining errors in measuring angular coordinates (angular noise) of a radar target presented as a multipoint model is considered. A method for calculating errors in the angular coordinates of targets is proposed, which is based on determining the gradient of the phase field of the wave at the point of reception of reflected signals. Analytical relations have been obtained that make it possible to calculate the direction of arrival of waves with an arbitrary number and location of points in a multipoint target model. For various types of targets — low-flying, group and single targets with a different number of points, calculations of errors in the angles of arrival of radio waves were carried out. In this case, angular errors are understood as the deviation of the direction of arrival of reflected radio waves from the direction of the geometric center of the target. The analysis of the causes of abnormal errors in measuring angles for the considered cases of numerical calculations is carried out.

An algorithm has been developed for the parametric synthesis of reflective multistage amplifiers using reactive, resistive, mixed and complex matching four-poles connected to a feedback circuit. The possibilities of synthesizing such amplifiers using the reflection coefficient at the input and output of a radio device are considered. The interrelationships between the elements of the classical feedback transmission matrix, optimal according to the selected criterion, are determined. The frequency dependences of the resistances of the two-pole part of the indicated types of four-pole resistances are obtained, which are optimal according to the criterion of ensuring the specified frequency characteristics. Dual permutations have been established that make it possible to determine the input resistances for structural circuits of the “nonlinear part — additional four-pole” type with known expressions for the output resistances of structural circuits of the “additional four-pole — nonlinear part” type and vice versa. In this case, the theory of four-poles, methods of matrix algebra, parametric synthesis of microwave control devices, decomposition and mathematical analysis of the frequency characteristics of reflective amplifiers are used.

Self-modulating and chaotic oscillations in a system of two coupled oscillators excited by an external periodic force are considered. It is assumed that the first oscillator has cubic nonlinearity and is connected to the second oscillator by a quadratic coupling. Two examples of problems leading to such a model are given: the first task is the task of exciting powerful hypersound in a ferrite plate with magnetically elastic properties; the second is the task of exciting electromagnetic noise vibrations in a ferrite disk placed in an electrodynamic resonator. It is noted that both problems can be reduced to solving a simplified system of two shortened oscillatory type equations, the first of which corresponds to a magnetic oscillator, and the second to an elastic or electrodynamic one. Time-based oscillation scans, parametric portraits for the displacement and its derivative, as well as frequency spectra of excited oscillations in a wide range of excitation amplitude are obtained. Two main oscillation modes have been identified: mode No. 1 — multiharmonic regularized, mode No. 2 — multiharmonic quasi–chaotic, which, starting from regular, alternately replace each other as the level of excitation increases.

The flow structure and the Laplace field implementing this structure are investigated on models that include various options for specifying the beam axis and the potential on it, taking into account the asymptotics of the antiparaxial theory during emission in the T-mode. The problems of non-uniform distribution of parameters on the cathode surface and the formation of the ends of a ribbon beam with a cross-section deformed due to the drift velocity are discussed.

The numerical properties of applying the method to compute the periodic solutions in the analysis of circuits with memristor devices are considered. The modification of the iterative procedure is proposed, which makes it possible to improve numerical properties in simulation of periodic modes by taking into account the characteristics of memristors. Examples of simulation confirming the operability of the developed computational procedure are given.