Introduction. When manufacturing printed circuit boards (PCBs), including their prototypes, the proper alignment of PCB layers is mandatory. While the causes and preventive measures against misalignment in PCBs manufactured using conventional technologies are known, research into alignment errors in 3D-printed PCBs is still ongoing. Another task regarding 3D printing, which is related to topological accuracy (alignment errors in particular), consists in ensuring the opportunity to remove the printed part of the product in order to perform operations thereon, such as embedding components, followed by its return and continuation of the printing process.

Aim. Numerical estimation and analysis of the causes of layer-to-layer alignment errors in PCBs manufactured using 3D printing.

Materials and methods. The research was conducted using the following materials and equipment: Polyethyleentereftalaatglycol (PETG); an Ultimaker Cura slicer; an Ender 3 S13D printer; a brass nozzle with a diameter of 0.3 mm. The study was conducted using the facilities of the Additive Technologies Center, Bauman Moscow State Technical University. Interlayer alignment errors are estimated by microsection analysis and X-ray inspection, as well as using the misalignment decomposition method described by Yu.B. Tsvetkov for electronics.

Results. The possibility of manufacturing PCB prototypes with three conductive layers is demonstrated, including a method for removing the printed part of the product and its further return in the printing process using printed pins. Large-scale distortions were found to make the largest contribution to the alignment error: on average, approximately 150 gm for each layer when compared to its 3D model and approximately 60 gm when comparing the topology of the top layer with the bottom layer. These values exceed the common misalignment value of 50 gm for the pin lamination process. This substantiates the need to control and minimize temperature effects, e.g., using 3D printers with a thermostatically-controlled chamber.

Conclusion. The conducted analysis of possible causes of misalignment emergence determines the significance of temperature gradients that occur during 3D printing. The proposed manufacturing method allows the printed part of the product to be removed and further returned into the printing process, which can be used to produce PCB prototypes with three conductive layers.

Introduction. Under the conditions of globalization, transportation of oil products by tanker fleets becomes one of the causes of man-made disasters in the water areas of seas and oceans. In this context, environmental monitoring acquires particular significance as a tool for ensuring timely detection of negative consequences of man-made disasters. This task is facilitated by recognition of images obtained from unmanned aerial vehicles with selection of those depicting the traces of man-made accidents or their consequences.

Aim. To develop approaches for carrying out automatic selection of input data obtained from unmanned aerial vehicles in the form of photo and video images at the preliminary stage of image recognition.

Materials and methods. The theoretical part of the study employed a classification method based on pattern recognition theory. Mathematical processing and calculation were carried out in the MATLAB environment. Simulation was conducted using the MathCAD environment.

Results. A series of experiments was conducted to select a basis for discrete wavelet transforms. Modeling was conducted using the study results of the sensitivity of the feature vectors of images formed on the basis of different types of wavelet transforms. A concept of image construction for the purposes of feature vector formation was developed.

Conclusion. An approach to the formalization of images for the purposes of feature vector formation is proposed. A metric of their contrast estimation is substantiated. It was established that the sensitivity of a recognition system based on the representation of images in the form of discrete wavelet transform matrices depends not only on the type of the mother wavelet, but also on the value of the scale parameter.

Introduction. The topic of implementing a dual-band mode of operation for director dipole antennas is represented by a wide range of works, almost all of which are dedicated to studying the properties of a classic dipole. However, the issue of end excitation of radiators for dual-band director antennas remains open. The development of such radiators requires a deep analysis both from the point of view of developing mathematical and electrodynamics models, which corresponds to the tactical and technical requirements of modern digital antenna arrays.

Aim. To substantiate a procedure for determining the initial appearance of a dual-band antenna exciter from the standpoint of the systems approach to the design of antenna elements and nodes. This procedure is suitable for a semi-automated design of more complex antenna systems.

Materials and methods. As part of the research, the input impedance of a dual-band system consisting of two active radiators and two passive directors was determined using the method of induced electromotive forces (EMF). Models of dual-band director radiators were developed using the CST Studio Suite 2021 full-wave electromagnetic simulation.

Results. The results of developing procedures for a semi-automatic design of antennas with a dual-band function of input impedance are presented. Following a comparative analysis, approaches to implementing the printed layout of an antenna comprising standard radio engineering components, which imply serial production, are proposed.

Conclusion. The proposed models can be used when designing director, turnstile, and cardioid antennas, as well as antenna arrays. These designs are analogous to antennas based on a classic central excited dipole.

Introduction. When operating antennas in various radio-electronic systems, the influence of phase shifter (PS) failures on the characteristics of phased array antennas, waveguide-slot phased array antennas (WSPAA) in particular, should be taken into account. A review of publications shows a lack of research studies into failures of these elements.

Aim. Research of WSPAA characteristics in the event of PS failures, when their phase takes a value equal to zero instead of the required value.

Materials and methods. Statistical modeling methods were used to study the impact of PS failures on WSPAA characteristics. Calculations were carried out using a PC and the Mathcad 15 applied mathematics package.

Results. An algorithm for statistical modeling of the impact of PS failures on WSPAA characteristics is proposed. A relationship that connects the radiation pattern with the statistical sample volume and the number of failed PSs is presented. Malfunctions of emitters from 5 to 35 out of 50 elements were investigated. Changes in the following characteristics were obtained: standard deviation - from 0.064 to 0.18; relative values: radiation pattern width - from 8 to 18 %; level of side lobes - from 13 to 59 %; radiation power - from 0.9 to 0.3.

Conclusion. The results obtained can be generalized and used in radio-electronic systems with antenna arrays at the stage of their development. Future work will address the influence of PS failures with phases being established randomly and with random values, as well as PS failures in which power does not pass into the emitter. Another important area concerns compensation of distortions resulting from failures of antenna elements.

Introduction. Constant false alarm rate (CFAR) detectors have found application in synthetic aperture radar (SAR) systems. The operating principle of a classic cell averaging detector (CA-CFAR detector) is based on comparing the decision statistics in the test resolution element with an adaptive threshold, which is calculated from signals in the reference cells. The decision statistic is an estimate of the signal power. Therefore, target signal detection is based on the brightness contrast of the test and reference resolution cells. Such a detector is optimal provided that the noise background is homogeneous. In cases where the background homogeneity is violated, the quality of detection deteriorates. There are several known methods for improving the quality of detection (GO-CFAR, SO-CFAR, OS-CFAR, etc.). However, the precise principle of detection by brightness contrast in such CFAR detectors remains unchanged.

Aim. To synthesize a CFAR detector that uses not only the brightness contrast between the test and reference resolution cells, but also the spectral differences of the signals.

Materials and methods. The proposed CFAR detector uses estimates of the algebraic moments of the power spectral density of signals in range cells, based on which three decision statistics are calculated containing information about the power, the position of the energy center, and the width of the signal spectrum. The decision about the presence of a target in the test cell is carried out according to the 2/3 rule (2 threshold overshoots out of 3 comparisons).

Results. A comparison of the proposed detector with the SO-CFAR detector, performed by computer simulation, showed that, under a signal-to-clutter ratio of -6 dB and a false alarm probability of 10^-4, the detection probability of the proposed detector was 0.933 versus 0.708 for the SO-CFAR detector.

Conclusion. The article proposes a three-parameter CFAR detector for a synthetic aperture radar system, in which the decision on the presence of a target in the test cell is made via estimation of the first three algebraic moments of the signal spectrum. The synthesized detection algorithm can also be used when detecting moving targets in SAR.

Introduction. Radar images of aircraft propellers can significantly improve the quality of their recognition and protection against simulating interference. Such images can be obtained using algorithms based on an inverse antenna aperture synthesis. A key factor determining the quality of image acquisition is the accuracy of the rotor blade rotation frequency measurement. In 2019, a method for measuring the blade repetition rate was proposed, which is based on convolution of the "secondary" signal modulation spectrum while simultaneously eliminating the influence of the Doppler frequency of the signal reflected from the aircraft body. In sequential analysis, the number of cycles is determined by the ratio of the maximum blade repetition rate (hundreds of hertz) to the discrete frequency shift (thousandths of hertz). In this case, to solve the measurement problem, the required number of cycles should be hundreds of thousands, which is expensive in terms of practical implementation.

Aim. Development of a two-stage method for measuring the blade repetition rate, which allows the number of signal convolution cycles to be reduced by hundreds of times.

Materials and methods. The proposed method is aimed at implementing adaptation circuits to an a priori unknown rotor speed of an aircraft, which can be determined based on the blade rotation frequency. The method involves measuring the blade frequency in two stages: a rough measurement of the blade frequency rate followed by its accurate measurement within the limits of the maximum errors of the rough measurement.

Results. A method for a two-stage measurement of the blade repetition rate as applied to the construction of radar images of aircraft propellers is proposed. The feasibility of the method is illustrated by the example of a signal reflected from a Mi-8 helicopter. The requirements to the measurement error of the blade repetition rate and to the frequency analysis step at the precise measurement stage are formulated. The requirement to the repetition rate of probing signals is substantiated, the fulfillment of which ensures an unambiguous restoration of the spectrum of "secondary" modulation of the signal reflected from the blades of a propeller-driven aircraft.

Conclusion. The developed method for a two-stage measurement of the blade repetition rate ensures the adaptation of algorithms for constructing radar images of aircraft propellers to their rotation frequency.

Introduction. Computer simulation and prototyping software can simplify the design process of complex information and measurement systems significantly, including radar systems and complexes. At present, a number of software packages are used to solve these problems to varying degrees. However, these software packages are either versatile, thus being incapable of taking the specifics of radar operation into account and requiring hand-made implementation of mathematical models for simulating radar signals, or are aimed at a narrow range of prototyping problems and algorithm development for processing radar information for a strictly defined radar type (or even a specific model). Some software packages, such as MATLAB, offer extension packages that allow radar signal simulation for automotive radars, as well as radar signal processing; however, these packages cannot cover the full range of simulation and prototyping tasks.

Aim. Analysis of current software packages for simulation and prototyping of radar systems and complexes, justification of the demand and development of the concept and architecture of a software package for simulation and prototyping of radar systems and complexes.

Materials and methods. Systems approach, architectural and conceptual software design, system analysis, criterion analysis. Results. The criteria that software packages for simulating and prototyping of radar systems and complexes must meet were determined. A comparative analysis of the existing approaches and software packages that solve problems arising at various stages of radar development was carried out. A list of requirements for such a software package was compiled, its concept and architecture was developed, and some features of its implementation were determined.

Conclusion. The developed architecture allows creation of a versatile software package which could provide solutions to the problems of simulation and prototyping of radar systems and complexes using a single software package. The applied principles of modularity and decomposition ensure versatility and a high potential for adapting software modules, including for creating software for controlling radar prototypes and visualizing radar data in real time.

Introduction. Industrial monitoring of pulsed bremsstrahlung radiation is associated with a number of challenges. Russia produces only three dosimeters that can be used for measuring pulsed bremsstrahlung radiation with a pulse duration of less than 10 gs. These dosimeters, in addition to being rather expensive, have a number of significant restrictions on the energy range (10 MeV) and the minimum pulse duration (10 ns). The DKG-RM1621 dosimeter with a Geiger-Muller counter can be used for dosimetry of photon radiation with energies up to 20 MeV. However, this device is not intended for dosimetry of pulsed radiation.

Aim. Development of a methodology for conducting radiation monitoring of pulsed bremsstrahlung radiation sources using dosimeters with Geiger-Muller counters.

Materials and methods. In 2021, measurements of the dose rate of pulsed bremsstrahlung radiation with a maximum energy of 3.0 MeV at pulse repetition rates of 50, 100, 150, 200, 250, 300, and 400 Hz were carried out using DKS- AT1123 (as a reference) and MKS-AT117M dosimeters with a Geiger-Muller counter.

Results. A technique was developed for correcting the results of measuring the dose rate of pulsed bremsstrahlung radiation by a dosimeter equipped with a Geiger-Muller counter, which allows the dose rate of pulsed bremsstrahlung radiation to be measured with an additional error of less than 15 % in a practically significant range of dose rates. For the MKS- AT117M dosimeter at a pulse repetition rate of 400 Hz, this value was 320 gSv/h, which is sufficient for most practical tasks in radiation monitoring.

Conclusion. The feasibility and possibility of successful application of dosimeters with Geiger-Muller counters for dosimetry of pulsed bremsstrahlung radiation using the proposed measurement technique with a limitation on the maximum measured dose rate is shown.

Introduction. Analysis of locomotor activity is essential in a number of biomedical and pharmacological research designs, as well as environmental monitoring. The movement trajectories of biological objects can be represented by time series exhibiting a complex multicomponent structure and non-stationary dynamics, thus limiting the effectiveness of conventional correlation and spectral time series analysis methods. Recordings obtained using markerless technologies are typically characterized by enhanced noise levels, including both instrumental noise and anomalous errors associated with false estimates of the location of the points of interest, as well as gaps in the trajectories, promoting an urgent need in the development of robust methods to assess the characteristics of locomotor activity.

Aim. Development of robust methods for assessing the characteristics of locomotor activity capable of efficient processing of noisy recordings obtained by markerless video-based motion capture systems.

Materials and methods. In order to assess the characteristics of locomotor activity, the relative movements of body parts of laboratory animals were analyzed using the stability metrics of the mutual dynamics of their trajectories, their relative delays, as well as the relative duration of the recording fragments when relatively stable mutual dynamics could be observed. The local maxima of the cross-correlation function of two body fragments, the minima of the standard deviation of the difference between their Hilbert phases, as well as their relative delays, were used as the metrics of mutual dynamics.

Results. The considered phase metrics were shown to explicitly reflect changes in locomotor activity, while the assessment of time delays using phase metric was shown to be prone to periodic error. The above limitation could be largely overcome using the correlation metrics, assuming that phase and correlation metrics could be combined.

Conclusion. The proposed robust methods provide stable estimates of the characteristics of locomotor activity based on markerless video capture recordings, altogether increasing the efficiency of diagnostic procedures and assessment of the therapeutic effect during rehabilitation.