Introduction. At present, the noise immunity of receiving multi-position signals in channels with variable parameters is improved using various signal structures (SS). In particular, in communication systems and the DVB-T2 television standard, these are quadrature amplitude modulation (QAM) signals with transformed constellation diagrams. However, in practical calculations of communication systems, the existing SS models fail to take into account the random nature of changes in the phases of the transformed signal constellation. This, in turn, leads to a discrepancy between the analytical value of error probability and its real value due to asynchronism in the radio link. The SS model proposed in this paper and the obtained analytical ratio take into account the introduced phase distortions in channels with variable parameters.
Aim. Development of theoretical proposals for improving the efficiency of receiving QAM signals in radio channels with variable parameters.
Materials and methods. The considered transformed SS model and the resulting analytical relation are described on the basis of communication theory and signal theory in the subject area of noise immunity research methods. This, in turn, enables analysis of the effect of phase distortions in channels with variable parameters on the error probability of receiving QAM signal elements.
Results. A transformed SS model with improved energy characteristics and an analytical relation for calculating the error probability of receiving QAM signal elements are proposed. Theoretical proposals for improving the noise immunity of receiving multi-position signals in channels with variable parameters are formulated.
Conclusion. The developed theoretical proposals for improving the noise immunity of multi-position quadrature signal structures in channels with variable parameters make it possible to improve their energy characteristics, taking into account phase distortions introduced by the communication channel. The presented dependence makes it possible to evaluate the relationship between the values of the probability of a pair error of receiving QAM signal elements and the limits of the change in phase shifts introduced by a communication channel with variable parameters. Future research will address the development of scientific and practical proposals for improving the noise immunity of quadrature multi-position signals, including an algorithm and block diagram for compensating phase shifts introduced in communication channels; processing of the amplitude values of the signal, which assumes the difference in the paths in terms of frequency-polarization and determines the accuracy of eliminating phase distortions.

Introduction. The technology of printed circuit boards (PCBs) is widely used in modern electronic instrumentation. PCBs for the microwave frequency range are made based on foil composite materials, in particular, polytetrafluoroethylene (PTFE). At the moment, there is no domestic production of such a class of materials. Information concerning foreign manufacturing technologies in this field and the influence of the filler on the characteristics of the composite material remains confidential. Therefore, research into the properties of composite materials for microwave applications with properties similar to foreign analogues seems relevant.
Aim. Experimental determination of the dependence of the electrical and mechanical properties of a composite material based on polytetrafluoroethylene depending on the concentration and size of the titanium dioxide fraction.
Materials and methods. Experimental determination of the dependence of the electrical and mechanical properties of a composite material based on PTFE depending on the concentration and size of the titanium dioxide fraction.
Results. The results of an experimental study of the mechanical properties and microwave parameters of experimental samples of composite material based on PTFE are presented, namely: composite material with 10 % content of ceramic titanium dioxide powders (fraction size 10, 49 and 126 µm); composite material with 5, 10 and 15 % content of ceramic titanium dioxide powder (fraction size 49 µm for polytetrafluoroethylene and 126 µm for titanium dioxide).
Conclusion. The results obtained demonstrate prospects for using compositions based on PTFE and titanium dioxide powder as a basis for microwave materials. A correlation was established between the percentage of the introduced ceramic filler and the microwave parameters of the material. The studies demonstrated a slight difference in the microwave properties of the manufactured composite material samples with a different ratio between the particle sizes of titanium dioxide and PTFE. However, a significant decrease in their mechanical properties was observed.

Introduction. Direction finding errors degrade the performance of any direction finding system. In the case of a phase direction finder, the cause of errors, among other things, is related to the non-identity of the receiving channels. Research into the influence of antennas on direction finding errors, as well as a search for ways to reduce these errors, appear to be relevant tasks in terms of improving the quality of direction finding systems.
Aim. To study the influence of millimeter-wave antennas on the errors of the phase direction finder.
Materials and methods. For a series of four millimeter-wave antennas, the following characteristics were obtained: spatial gain readings, phase diagram readings, and complex reflection coefficient values. Based on the characteristics obtained for several spatial directions, matrices of characteristics were formed. For each matrix, the L norm was found. Based on the differences between the obtained L norms, conclusions were drawn about the degree of difference between the antenna characteristic matrices. According to the degree of similarity between the characteristic matrices, the antennas were grouped in pairs. The L norms of the antenna matrices from one pair differed insignificantly compared to the differences between the L norms of the antenna matrices from the second pair. With each pair of antennas, the bearing and direction-finding errors were determined in the range of angles φ: −15…15° in increments of 1°. The values of direction-finding errors obtained for each pair of antennas were compared with each other.
Results. The obtained values of direction-finding errors for two alternately used pairs of antennas differ in the entire considered range of angles. Moreover, a pair of antennas with a smaller difference L norm is characterized by a lower level of direction-finding errors. At most points in the angular range, the difference in DF errors for two pairs of antennas falls within the range of 0.05 to 0.1°. At the boundaries of the angular range, the direction-finding errors increase, with the largest difference of 0.5° being observed at an angle of ϕ = 15°.
Conclusion. Differences in the characteristics of antennas installed in the same phase-metric base lead to an increase in direction finding errors. A method for quantifying the non-identity of antennas is proposed. The proposed method can be used to group antennas in phase-metric bases, which will reduce direction-finding errors by the phase method.

Introduction. Modal reservation (MR) is a new way of reserving electrical circuits by means of strong electromagnetic coupling between their conductors, which not only increases their reliability, but also ensures their electromagnetic compatibility. Although showing much promise for critical radio electronic devices, MR has so far been studied exclusively at room temperature, without taking climatic conditions into account.
Aim. Presentation of the results of an experimental study into the frequency characteristics of printed circuit boards (PCBs) with MR based on coupled microstrip lines under climatic impacts in the form of low and high temperatures to evaluate the MR effectiveness before and after failures.
Materials and methods. PCB prototypes based on a microstrip line from a domestic material of the STF brand without and with MR (before and after two types of failure) were manufactured at the Polyus research and production center, Tomsk, Russia. These prototypes simulated the device operation before and after two types of failures. Using a vector network analyzer, frequency dependences of S-parameters of the prototypes were experimentally investigated in a heat-cold climatic chamber at temperatures ranging between minus 50 and 150 °С. Transmission and reflection coefficients in both directions of signal propagation were measured.
Results. It is shown that for the working circuit of PCBs with MR, before and after failures, an increase in temperature from room temperature to 150 °С leads to a decrease in the transmission and reflection coefficients in both directions (to a maximum of 2 dB and 29 dB, respectively). Conversely, a decrease in temperature results in an increase in these coefficients (to a maximum of 0.8 dB and 23 dB, respectively). At low and high temperatures, a shift of resonances (up to 500 MHz) towards high and low frequencies, respectively, is observed.
Conclusion. The MR effect is shown to remain after failure, having almost no influence on the useful signal, except at high temperatures, at which the operating frequency range of the useful signal can be significantly reduced. Future research should be aimed at reducing the sensitivity of the characteristics to temperature changes by means of selecting other PCB materials, as well as at investigating the radiated emissions from PCBs with MR before and after failures under the impact of climatic conditions.

Introduction. The current data monitoring and collection systems produce a growing amount of generated information. Such factors, as the increasing sampling rate of ADCs and the increasing speed of systems for primary processing, receiving, and transmitting information, etc., make the systems operate almost at the bandwidth limit of data transmission interfaces. In some applications, such a flow is redundant and can be optimized through the use of various algorithms for the primary processing of information. However, in some applications, reducing the data flow is impossible, since the received information is processed with a delay. Therefore, the development of a software methodology for controlling and collecting data in the system of automatic monitoring of the sea surface by a hydrological radiolocation system seems a relevant research task.
Aim. To synthesize a methodology and to develop software for controlling the information system of radar monitoring of the sea surface.
Materials and methods. System approach, software architectural and algorithmic design, software quality management methods, system analysis, Qt framework, C++ programming language.
Results. A working methodology for designing software for controlling information and measurement technologies with a large amount of generated data was obtained. The effectiveness of the methodology and software quality were confirmed by control tests. A 3-month autonomous testing of the stability and reliability of the system was carried out. Detection of data loss in the system comprised less than 0.002 %, thus not exceeding the specified critical level of 0.5 %.
Conclusion. The developed methodology can be used in designing software for controlling information and measuring systems generating a large amount of data. The approaches used to build a multithread software architecture with asynchronous data flow control has shown their high efficiency.

Introduction. Track detection is one of the main tasks to be solved in trajectory processing. This task can be efficiently solved using the Hough Transform. A track is considered detected if the number of position measurements received in a number of consecutive radar scans and falling into the same cell of the parameter space (accumulator) has exceeded the detection threshold. However, the effective practical application of the Hough transform requires a sufficiently long time of measurement. Under a small number of scans given for track detection, measurements are also accumulated in those accumulator cells where their traces intersect. Therefore, in order to detect true tracks, additional processing is required to distinguish measurement clusters from different targets based on their geometric proximity. In addition, a large amount of memory and computational operations for the accumulator maintenance significantly increase the computation load of the trajectory processor.
Aim. To design a simple and false-detection resilient algorithm for detecting tracks without the Hough accumulator in the processor memory.
Materials and methods. In the proposed algorithm, the construction of measurement traces in the Hough accumulator followed by selection of cells with the largest number of traces passed through them is replaced by computation of the cross correlations of the traces and clustering of measurements based on the maximum similarity of their traces.
Results. Mathematical simulation with the scenario parameters selected in the paper confirmed the accuracy of the proposed algorithm in detecting all tracks existing in the radar field of view and its efficiency in conducting error free association of target position measurements.
Conclusion. A false-detection resilient algorithm for track detection was created based on the Hough transform. The algorithm does not require the Hough accumulator in the processor memory.

Introduction. The problem of increasing the efficiency of existing photodetectors and creating their new types attracts much research attention. Among new photodetector types are photosensitive structures based on cascade concentrators, whose operational principle involves the absorption of optical radiation followed by its reemission at a longer wavelength and radiation concentration onto a highly efficient small-area photodetector. The absorption and re-emission spectra of each cascade layer depend on the characteristics of the material used. Сolloidal quantum dots are among the most promising materials for cascade layers due to their manufacturing technology, which provides for accurate control over the photoluminescence maximum position. It seems highly relevant to develop and to study photosensitive structures with cascade concentrators of various shapes based on CdS, CdSe/ZnS, and PbS colloidal quantum dots.
Aim. To develop photosensitive structures with a wide-range sensitivity spectrum based on concentrators containing arrays of metal chalcogenide CQDs and to study their characteristics.
Materials and methods. Cascade photosensitive structures were manufactured based on layers made of polymethyl methacrylate and layers of colloidal quantum dots embedded in a polystyrene matrix.
Results. Three-layer concentrators were manufactured with different colloidal quantum dots in each concentrator layers. A 22 % increase in the output power was observed for a three-layer cascade structure based on different cascade layer materials compared to a similar structure using a single layer concentrator.
Conclusion. The conducted studies showed an increase in the efficiency of photosensitive structures with a cascade concentrator based on colloidal quantum dots of various types (CdS, CdSe/ZnS, and PbS) in the cascade layers.

Introduction. In previous works, the authors considered the frequency characteristics of sensitive elements made of various materials in the form of a ring resonator on surface acoustic waves (SAW), along with their fixing methods in the housing, the influence of external factors, and an optimal topology of the interdigital transducer of the ring resonator. Further, the need arose to study the dependence of the sensitivity of the sensitive element and the maximum acceleration load on its dimensions, as well as to analyze the characteristics of the manufactured experimental samples in comparison with the simulated values.
Aim. To determine optimal dimensions of the sensitive element of a ring resonator and to confirm the adequacy of the constructed models by comparing the characteristics of experimental samples with those obtained by computer simulation.
Materials and methods. The theoretical part of the research was carried out using the finite element method. Mathematical processing was implemented in AutoCAD and COMSOL Multiphysics.
Results. Three overall dimensions of the sensitive element of a ring resonator were proposed: 1500, 3000 and 4500 µm. The characteristics of sensitive elements made of lithium niobate with the above dimensions were studied. Thus, the resonance frequency for 1500, 3000 and 4500 µm samples comprised 207.99, 104.10 and 68.99 MHz, respectively. The maximum acceleration experienced by a cantilever with a radius of 1500, 3000 and 4500 µm was found to be 191 132, 84 958 and 37 514g, respectively. Dependence graphs of the maximum acceleration and sensitivity on the ratio of the radius of the console to its height are presented. The adequacy of the constructed model was confirmed, i. e., the resonance frequency for 1500, 3000 and 4500 µm experimental samples comprised 218.17 MHz (4.67 % discrepancy with computer simulation), 109.23 MHz (4.69 %) and 72.88 MHz (5.34 %), respectively.
Conclusion. The sensitivity and maximum acceleration load of the sensitive element of a SAW ring resonator directly depends on the ratio of the cantilever radius to its height, with higher sensitivity values correlating to lower values of maximum acceleration load. For each material, these dependencies are unique. The interdigital transducer bus size has little effect on the frequency response. The previously presented simulations were confirmed by experimental samples with a difference in resonance frequencies of less than 5.5 %.

Introduction. In the gyrocompassing mode, the initial heading angle of a platformless inertial navigation system (PINS) is determined based on the data obtained from accelerometers and gyroscopes that measure the projections of the gravitational acceleration vector and the Earth’s angular velocity vector on the axes of the body coordinates system in the PINS initial stationary mode. Due to unavoidable circumstances, such as bias instability and random noise in the accelerometer and gyroscope signals, much time is required to obtain the sufficient amount of sensor data for achieving the necessary accuracy of useful measurement values by the averaging method. In this context, in order to reduce the time of the gyrocompassing mode, data processing methods should be used to eliminate the bias instability and random noise in the signals received from PINS inertial sensors.
Aim. To develop a method for suppressing random noise and reducing bias instability in the signals of inertial sensors, thereby reducing the time of the gyrocompassing mode of PINS and providing for the required accuracy of its initial heading angle determination.
Materials and methods. An autoregressive (AR) model was used to simulate random noise in the measured sensor signals followed by its filtering using a Sage-window square-root unscented Kalman filter (SW-SRUKF).
Results. A mathematical model describing random noise in the PINS inertial sensors in the stationary mode was derived. A methodology for suppressing random noise was proposed. The effectiveness of the proposed method was tested on actual data, with the results presented in the form of figures and tables.
Conclusion. A method for eliminating the bias instability and random noise of PINS accelerometers and gyroscopes was proposed based on AR model and SW-SRUKF. The accuracy and effectiveness of the proposed method was confirmed by processing actual inertial sensor data. The results obtained are significant for reducing the initial alignment time of a PINS in the gyrocompassing mode.

Introduction. Arrhythmia or irregular heartbeat occur when the heart’s electrical system is disorganized or out of sync, which may cause strokes, sudden cardiac death, and other complications. The introduction of an automated classification of arrhythmias based on deep learning could facilitate the decision-making process by saving time and labor resources.
Aim. To study the performance of a modified arrhythmia classification improved by using binary images of segmented ECG signals with combinations of orthogonal and surface signals.
Materials and methods. This article studies an arrhythmia classification based on binary images of surface and orthogonal ECG signals. The data labeling was automated using the Python programming language. Initially, all signals are subjected to preprocessing followed by their plotting and segmenting in 2-second windows. Next, those segments are saved as RGB images followed by their conversion into binary images, where the signal is white, and the background is black. Finally, the pre-trained Alexnet model is used to classify nine classes, where each surface ECG and orthogonal lead is classified separately.
Results. The performance of the model is evaluated by the mean accuracy, precision, F1-score, and confusion matrix of all leads. The results of a parallel classification of 12 lead ECG are better than those for the orthogonal leads. All leads with accuracy, precision, and F1-score equal to 0.84, 0.78, and 0.71, respectively.
Conclusion. The performance of the model was evaluated for three cases: 12 surface ECG leads, orthogonal leads, and all leads. The calculated mean values of accuracy, precision, and F1-score for each case confirmed the sufficiency of the 12-lead surface ECG for classifying nine different types of arrhythmia using binary images of ECG segments.