Radiotehnika i èlektronika

The article is devoted to the problems of analysis and synthesis of dual-polarization ultra-wideband reflectarrays and is relevant for arrays of UWB elements of extended length such as Vivaldi antennas and TEM-horns. Synthesis and analysis are carried out in the approximation of a locally periodic array, when each of its elements can be assigned a Floquet cell. A review of the literature on UWB reflectarrays is carried out and it is shown that in most published works the dependence of the phase of the Floquet cell transmission coefficient on the angle of incidence and polarization of the exciting wave is not taken into account in the process of synthesis of the array. This article presents a procedure for the approximate synthesis of a dual-polarization UWB reflectarray taking into account the above effects. An approach to the analysis of the UWB RAA is proposed, based on the numerical calculation of the Floquet cell scattering matrix in combination with the successive approximations method. A comparison of the solutions at the first and second iterations is carried out, and the questions of further solution correction by increasing the order of approximation are discussed.

Using numerical modeling, a study was carried out of the matching and radiation characteristics of a flat in-phase two-dimensional - periodic over-band antenna array of flared-notch horns depending on the period and length of the array elements, input and output impedance, type of feed lines and screen shape. A 64-way power divider with outputs in the form of symmetrical two- strip lines has been developed and studied, and an 8 × 8 array of elements with a power divider as a power feed system has been studied. It is shown that the array with the U-shaped screen provides an operating frequency bandwidth of more than 20:1.

The article presents the results of experimental studies of the dependence of the propagation constant of an electromagnetic wave along the conductors of HF band near ground antennas on the properties of the soil and a comparison with known analytical expressions. The accuracy characteristics of known formulas are estab-lished and an assessment of their applicability for solving practical problems is given.

The problem of creating a system for constructing two-dimensional images in radio light based on correlation reception is considered, where radio light is understood as ultra-wideband noise-like microwave radiation. A mathematical model was developed, with the help of which images of radio light lamps were obtained, also the modeling results were used to create a real layout of the receiving system. Experiments were carried out with a prototype system for constructing two-dimensional images in radio light using correlation-based reception, with the help of which images of two radio light sources with a difference in radiation level of 12 dB were obtained.

The phenomenon of non-stationary delay in excitation of high-amplitude chaotic oscillations in a system of two coupled oscillators is considered. A brief description of two real physical systems that allow excitation of chaotic oscillations with non-stationary delay is given. It is shown that oscillations in both systems can be de-scribed based on the same model of two coupled oscillators, one of which is non-linear and the other is linear. A system of two second-order differential equations is given for such a model. This system is simplified while preserving the kernel that provides the effect of delay in high-amplitude chaotic oscillations. The possibility of replacing external excitation in the system with the initial displacement of one of the oscillators is considered.

New experimental data have been obtained indicating the following two reasons for the previously discovered significant decrease in the duration of the intrinsic picosecond emission of the Al_xGa_1–xAs–GaAs–Al_xGa_1–xAs heterostructure emerging from its end in a preferred direction: 1) the emission reflected from the end returning to the active region takes up a significant portion of the population inversion energy that would otherwise be spent on generating emission moving toward the end; 2) the resulting inhomogeneities in the reflected emission caused such a switching of the states of the multistable photonic crystal induced in the heterostructure by its emission that the forbidden zone for the emission emerging from the end in a preferred direction grew, and the emission trajectories changed in the heterostructure and, as a consequence, in the air space.

The results of an experimental study of new technological solutions for the creation of basic elements in compact bio-inspired spiking neurons are presented: we are talking about nanoscale Josephson contacts with a gold wire in the field of weak communication. The design of the neuron as a whole has been found, for which the low capacitance of nanoscale contacts, which was previously one of the main limitations in practical implementation, is no longer a problem. The operability of the proposed circuit solution is confirmed by numerical modeling. On this basis, the topologies of the bio-inspired neuron were developed. The results obtained open new possibilities for the creation of high-performance and energy-efficient neural networks, which can have a significant impact on the development of artificial intelligence and quantum technologies.