Introduction. In recent years, unmanned aerial vehicles (UAVs) have been a rapidly advancing field. In all areas of UAV application, positioning accuracy is of particular importance. For outdoor environments, satellite navigation systems (such as GPS) are always the method of choice. However, for indoor environments, GPS signal weakening becomes a serious obstacle for determining the UAV location. A number of studies have been carried out to develop various indoor positioning technologies that meet the criteria of compactness and light weight, thus suitable for small aircrafts, including optical flows, inertial measurement systems, ultrasound, etc. However, there is a lack of comparative studies reviewing indoor positioning technologies for autonomous UAVs. The existing reviews fail to provide a comprehensive assessment of such technologies and their operational principles according to the main criteria. In this connection, this paper aims to review modern indoor positioning technologies and their operational principles, conducting evaluation according to such criteria as accuracy, operating range, cost. The assessment of promising machine vision-based technologies is carried out.

Aim. To classify modern indoor navigation technologies for UAVs; to assess the technologies under consideration according to various criteria.

Materials and methods. The current technologies for UAV indoor positioning were classified by the signal type used for connection and their capability to process information without external signals. The technologies were assessed according to the following criteria: accuracy, operating range, cost, as well as their advantages and disadvantages.

Results. А classification and evaluation table of UAV indoor positioning technologies is proposed; a review of the current developments in the field is given.

Conclusion. A review of UAV indoor positioning technologies has been carried out. In addition, the prospects of machine vision-based technologies are outlined.

Introduction. Electromagnetic shielding is used as an additional design tool to ensure electromagnetic compatibility of electronic devices. The shielding material is selected based on its electrophysical parameters at the design stage of electronic devices, taking its electrical and operational characteristics into account. The shielding effectiveness (SE) of composite, layered, or fabric materials with a high electrical conductivity and relative magnetic permeability in a wide frequency range (10 Hz…10 GHz) is difficult and, in some cases, impossible to assess a priori. At the same time, the number of studies in this direction is currently limited.

Aim. To generalize models and methods for calculating and measuring the insertion losses (IL) and SE of materials using dual and coaxial TEM cells in a wide frequency range.

Materials and methods. A method for calculating IL for the electric (E) and magnetic (H) components of the field based on the measured S parameters in a dual TEM cell is described. Expressions for calculating an unloaded dual TEM cell are proposed. These expressions differ in terms of considering the thickness of the material and the tooling that prevents sagging of thin materials, thus allowing the difference between the measured and calculated values of S parameters to be reduced to 3.2 dB. Methods for measuring and calculating the SE of composite materials are described. The results obtained using these methods are compared with those obtained by a standardized method for SE calculation.

Results. The frequency dependencies of the IL for the E and H fields calculated on the basis of the measured S parameters of a dual TEM cell with a cotton and knitted shielding fabric placed inside are presented. The results obtained by the classic and electrodynamic modeling are compared with experimental results for a composite material in a new patented coaxial TEM cell.

Conclusion. Models and methods for calculating and measuring IL and SE can be effectively used for a relatively rapid control and testing of new and available shielding materials, taking the above assumptions and limitations into account. 

Introduction. Due to the depletion of the frequency resource in the Ku frequency range, satellite communication systems are being actively developed in higher frequency ranges, i.e., Ka and Q. Satellite communication earth stations in these ranges are characterized by receiving and transmitting at widely spaced frequencies (1.5 times or greater). Mirror antennas used in communication stations must ensure the formation of appropriate radiation patterns in two separated ranges. Therefore, due to the high requirements for their technical characteristics, the development of feeds for such antennas is associated with a number of currently unresolved difficulties.

Aim. Development of models and prototyping of a dual-band feed based on a coaxial circuit and a feeder path using a narrow-band transition from a rectangular waveguide to a round one.

Materials and methods. Calculation and research of the developed design of a dual-band irradiation system was carried out using the CST Studio Suite software and specially developed add-on programs that significantly simplify and speed up the work.

Results. A prototype of the dual-band feed EIF5.468587.001 was developed, which ensures the formation of the radiation pattern of a mirror antenna in the receiving range (19.172…19.792 GHz) with an efficiency of no less than 46 dBi and the level of the first side lobe of no more than 20.1 dB, and in the transmitting range (43.924...44.524 GHz) with an efficiency of no less than 52.7 dBi and a first side lobe level of no more than 16.7 dBi. A comparative analysis of the developed feed model with a serial sample as part of the 08150.6220-0 antenna of a satellite communications earth station was carried out.

Conclusion. The EIF5.468587.001 feed produced as a result of the work makes it possible to form an axisymmetric pattern of a mirror antenna with a higher efficiency (by 0.7 dBi in the receiving mode and 1.4 dBi in the transmitting mode) and with the lowest level of off-axis radiation compared to the feed manufactured by JSC ISS as part of the 08150.6220-0 antenna and currently used as part of a satellite communication station.

Introduction. Modern computer simulation tools can be used to analyze complex waveguide structures channeling electromagnetic energy. In order to verify the obtained calculation results, they should be compared with a known "exact" value followed by calibration of the considered electrodynamic model. The desired value can be found using the method of Fourier transform, which allows the propagation constant in a regular rectangular waveguide with partial filling with a dielectric to be determined and its channeling properties in various wavelength ranges to be evaluated. Aim. Construction of a computational model for calculating a regular waveguide with an arbitrary arrangement of the dielectric on the cross section by the Fourier method, determination of the dispersion characteristics of the analyzed structures in the millimeter wavelength range.

Materials and methods. A mathematical model for the analysis of a waveguide with partial dielectric filling is based on Maxwell’s equations using boundary conditions for tangential and normal components of the electromagnetic field.

Results. A numerical analysis of the dispersion characteristics of structures with complex dielectric filling was carried out. A methodological approach to constructing a computational model for searching for the propagation constant in a rectangular waveguide with an arbitrary arrangement of dielectric filling is proposed. This approach can serve as the basis for analyzing layered dielectric structures with a complex cross-sectional shape and different values of relative permittivity.

Conclusion. The developed mathematical models made it possible to numerically evaluate the channeling properties of waveguides with dielectric filling in the microwave range.

Introduction. Solid-state electron multipliers (EMs) in matrix design, referred to as microchannel plates (MCPs), are an integral part of modern electronics. Recent progress in the field of molecular layering (ML) technology has offered an opportunity to tailor and improve the characteristics of solid-stated EMs by depositing thin layers inside the channels of these structures.

Aim. To study the possibility of depositing thin layers inside the surface of solid-state EM channels by ML in order to increase the secondary electron emission coefficient (SEEC) of such structures, thereby improving their performance characteristics.

Materials and methods. The ML method was used to deposit nanometer films of magnesium and aluminum oxides inside solid-state EM channels. The composition and structure of the layers were studied using scanning electron microscopy, X-ray photoelectron spectroscopy, secondary electron emission analysis, and atomic force microscopy.

Results. Thin aluminum oxide and magnesium oxide films were synthesized inside the micron channels of solidstate EMs. The layers exhibited high uniformity along the entire length of the channels. The layer thickness varied in the range from 2 to 30 nm. Layers with improved emission and protective characteristics were obtained. Comparative tests of MCP samples containing the synthesized films were carried out.

Conclusion. Good prospects for the application of emissive layers inside solid-state EM channels were shown. Structures with a high aspect ratio are promising objects for ML application. The creation of nanocomposite structures based on MCPs opens up the fundamental possibility of improving the current technology of producing electrooptic materials and devices. The MCP structures containing aluminum oxide layers obtained by ML technology were experimentally tested to detect beam collisions (FBBC) for work in detectors at the NICA accelerator complex. Following deposition of a 3.0 nm-thick Al₂O₃ film in the channels of the tested MCP samples, the signal amplitude increased by 1.5 times. The deposition of layers with a film thickness of 10 nm resulted in a 2.5-fold increase in the amplitude.

Introduction. Quantum well infrared photodetectors (QWIP) are characterized by a wide application range. A large market demand for such photodetectors determines the importance of elucidating the principle of their operation.

Aim. To carry out a research study into the influence of the AlGaAs potential barrier surrounding GaAs quantum wells on the QWIP operating bias voltage in the long-wavelength region of the spectrum (8…_{10 μ}m).

Materials and methods. QWIP experimental samples were manufactured based on the GaAs/AlGaAs semiconductor material system using molecular beam epitaxy. The photosensitive (active) region of the structures contained 50 GaAs quantum wells with a thickness of 50 Å thick separated by AlGaAs barriers. Quantum wells were doped in situ with silicon as a donor impurity. The wavelength of the maximum spectral sensitivity of all samples ranged within 8…_{9 μ}m. The barrier width was the variable parameter. After passing the planar modification process route, the current–voltage characteristics were measured in all structures.

Results. Reduction in the barrier thickness is capable of shifting the peak of photosensitivity towards the region of lower bias voltages with a slight increase in the dark current values.

Conclusion. The study of the influence of the applied bias voltage presents both scientific and practical interest. On the one hand, the results improve the current understanding of the behavior of the dark current in QWIP. On the other, they provide the possibility of managing the maximum current sensitivity, shifting it towards the region of the required operating voltages of the multiplexers.

Introduction. At present, acceleration sensors are in demand in various areas, from consumer electronics to space technology. Microaccelerometers exhibit the advantages of compact dimensions, light weight, and ease of integration with other components. The most common accelerometers are based on microelectromechanical systems. However, due to the fragility of elastic suspensions, these devices are characterized by low impact resistance, which impedes their application in highly dynamic objects with accelerations of up to 50 000 g. The authors propose to use microaccelerometers based on surface acoustic waves, which are solid-state monolithic structures capable of withstanding high shock loads. Previous work has proposed the concept of concentric electrodes, which are more energy efficient compared to linear designs. However, concentric elements are difficult to connect to the electrical circuit, due to the impossibility of connecting the busbars directly. Therefore, the authors describe and simulate five alternative methods for connecting the sensing element of such devices.

Aim. To select an optimal method for connecting the sensing element of microaccelerometers from the standpoint of maintaining the integrity of the electrodes and ensuring minimal influence on the propagation of surface acoustic waves.

Materials and methods. Finite element simulation in the COMSOL Multiphysics software.

Results. Five connection methods, including point-to-point wiring, removing the electrode sector, filling holes in the electrodes and substrate with metal, pulling wires through holes in the substrate and bringing out contact bars along the side face, were proposed and analyzed. Computer simulation was carried out. Graphs of the amplitude-frequency characteristic are presented.

Conclusion. Among the considered methods for connecting the sensing element, the most appropriate seems to be method No. 3, which implies holes in the electrodes and contacts on the bottom side of the substrate. Here, the graph of the amplitude-frequency characteristic practically coincides with that of the sensor without connections (reference). Future work will focus on creating a prototype and its experimental testing.

Introduction. In healthcare, breath analysis is increasingly used to detect diseases and monitor human health. Assessment of respiratory parameters, such as breathing frequency, is an important component in evaluating the overall state of the respiratory system. However, conventional methods, such as spirometry, have their limitations. Motion capture systems, such as marker-based video analysis, offer a promising and innovative approach for measuring respiratory parameters in conjunction with other investigations. This approach provides accurate data on respiratory activity without requiring specialized medical equipment. The use of such systems has the potential to significantly extend the scope of their application in rehabilitation and sports medicine.

Aim. Development of an algorithm for determining breathing parameters using a marker-based motion capture system. Development of an algorithm for optimal body position and best marker locations for determining breathing parameters. Analysis of control measurements.

Materials and methods. The data obtained as a result of synchronous recording of signals from an optical motion capture system and a spirometer were analyzed. The respiration rate was determined by spectral analysis and Fourier transform.

Results. An algorithm for analyzing and interpreting respiratory rate was developed. This algorithm not only considers body positions and marker locations, but also provides recommendations regarding their optimal placement.

Conclusion. The results obtained confirm the prospects of marker video analysis in assessing the frequency of respiratory movements using a motion capture system. Further studies will be aimed at taking physical activity into account with the purpose of developing effective diagnostic methods of external respiration parameters and respiratory disorders.

Introduction. Environmental pollution represents a serious threat to the public and ecological safety. Cross-reactive optical chemosensor materials and their combinations can be effectively used for timely identification of ecotoxicants in the vapor phase. The selection of chemosensor combinations for a reliable identification of toxic substances has received insufficient research attention. As a rule, all available chemosensor materials are used, although a smaller combination may be more reliable and informative.

Aim. To propose a method for selecting from a set of available chemosensory materials the optimal combination most suitable for identification of the required group of vapor-phase substances.

Materials and methods. A metric for assessing the quality of a chemosensor material combination for identification of toxic substances is proposed. This metric numerically describes the degree of orthogonality and the proximity of distributions of response vectors of the combination to the exposure to analyzed substances. On the basis of the metric, a method for selecting optimal combinations is formulated. Classification models based on the support vector method and the principal components method are used to classify responses of the combination of materials. The proposed method is tested on the example of selecting combinations of permeable fluorescent materials for identification of saturated vapor-phase nitroaromatic ecotoxicants and interfering substances.

Results. A combination of permeable fluorescent materials, sufficiently reliable for identification of vapor-phase nitroaromatic ecotoxicants, was determined. The possibility of rapid identification of toxic substances during the prolonged exposure of materials to their vapors is presented. It is shown that the quality metric is lower for a combination of all available fluorescent materials compared to a smaller combination selected via the proposed method.

Conclusion. An approach to solving the problem of finding an optimal combination of chemosensory materials for identification of the specified group of substances is proposed. The proposed method increases the reliability of identification of toxic substances while reducing the number of chemosensory materials involved in the process.