Introduction. Modern precision radio systems impose stringent requirements on the quality of the reference signal sources used. Various approaches are used to create sources of reference signals in the microwave range – micro-wave self-oscillators (SO). A promising direction in the development of such SO is SO with frequency-setting elements based on surface acoustic waves (SAW).

Aim. A review of international achievements in the development of frequency-setting elements based on SAW and respective SO.

Materials and methods. The selection of materials for a comparative analysis and generalization was carried out using available sources published over the past 30 years in well-known engineering journals, advertising brochures and websites of the manufacturers of devices based on SAW. The selection criteria included low values of the power spectral density of the frequency fluctuations of the generated signal, the presence of vibration protection, the presence of a thermostat, as well as the miniaturization and originality of the design.

Results. Specific features of various methods used for constructing microwave oscillators were analyzed. It is shown that the achievement of the best values of the power spectral density of frequency fluctuations in SO with frequency-setting elements on SAW is possible only with the use of two-port resonators. An analysis of the main technical characteristics of temperature-controlled vibration-resistant SO was carried out.

Conclusion. Despite the large number of different manufacturers on the world market (more than 20 companies) and the variety of different models of oscillators with frequency-setting elements on SAW (more than a 100 different models), only two companies produce oscillators resistant to external vibrations and acoustic noise.

Introduction. Construction of the radar image of a moving target and estimation of its velocity in synthetic aperture radars (SAR) presents a relevant research problem. The low quality of radar imaging is frequently related to the phenomenon of range cell migration (RCM). Conventional methods for RCM compensation, which are successfully used to obtain radar images of stationary targets, fail to provide the required quality when applied to moving targets. At present, a number of algorithms are used to solve this problem. However, the majority of them employ optimization procedures when searching for estimates of unknown parameters, which fact greatly complicates their implementation. An exception is the LvD algorithm, which implements double keystone transform to construct a radar image without using complex estimate search procedures. Radar images are constructed in the coordinates "longitudinal velocity - lateral velocity", which facilitates estimation of the target velocity components.

Aim. Development of an alternative algorithm based on the Mellin matched filter (MMF) for estimating the velocity and constructing the radar image of a moving target in a side-looking SAR.

Materials and methods. The derived algorithm is based on the invariance of the integral Mellin transform to the signal scale and uses the MMF to estimate the target velocity components.

Results. An algorithm for constructing the radar image of a moving target based on the MMF was synthesized. An analysis of the LvD algorithm showed its capacity for selecting the optimum scale factor when implementing a second KT. The conducted computer simulation of the MMF and LvD algorithms showed their equal accuracy. Under the same simulation scenarios, both algorithms yield effective estimates of the velocity components of a moving target when the signal-to-noise ratio is greater than -10 dB.

Conclusion. The proposed algorithm for constructing a radar image can be used in SAR systems designed for detection and velocity estimation of a moving target.

Introduction. Small unmanned aerial vehicles (UAVs) are a growing threat due to their possible use for illegal activities. Currently, passive coherent radar systems are widely used to detect, track and recognize moving targets, including small UAVs, which makes them a promising tool for use in modern airspace radar monitoring systems. At the same time, recognition of small UAVs becomes a challenging task due the possibility of confusing them with birds, particularly in maritime areas with large bird populations. In a search for new solutions to the problem of recognizing small UAVs, trajectory features can be used.

Aim. To analyze differences between the trajectory features of low-flying low-speed targets in order to verify the possibility of their use for recognition purposes.

Materials and methods. Real radar measurements of UAVs and birds obtained by a passive coherent radar system were used. Specific characteristics of the trajectory parameters of target classes were built using computer statistical modeling in the MatLab environment. Differences in the movement trajectory of targets were established by comparative analysis.

Results. Significant differences between the flight path of UAVs and birds were found. Specific features of the trajectory of small aerial targets of each type were investigated. On the basis of radar measurement, graphs of the characteristic trajectory parameters of UAVs and birds were plotted. The conducted comparative analysis allowed identification of the characteristics of the flight path of each target type in each movement segment. Trajectory features that can be used for recognition purposes were identified.

Conclusion. The practical significance of the proposed trajectory features and the possibility of their implementation in the development of an algorithm for recognizing low-flying low-speed radar targets using passive coherent radar systems was established. The knowledge of differences between the flight path of UAVs and birds can improve the quality of the UAV recognition problem.

Introduction. The increasing number of incidents involving unmanned aerial vehicles (UAVs) makes their detection in the aerodrome area an important task, which can be solved by specialized surveillance means. However, the application of such means requires certification procedures confirming the effectiveness and safety of their use. Therefore, in the short term, it seems reasonable to use standard technologies. In the approach sector, this task can be solved by precision approach radar systems. The small radar cross-section (RCS) of UAVs leads to a decrease in the maximum range and the appearance of blind spots, within which the vehicle cannot be detected.

Aim. Analysis of the possibility of detecting UAVs using a precision approach radar, assessing the maximum detection range, blind spots and developing recommendations for their reduction.

Materials and methods. An analytical method was used for determining the maximum detection range for a precision approach radar, taking into account UAV characteristics. A method for estimating the detection range of a low-flying target, taking into account the influence of the underlying surface, was also used.

Results. Using the example of the precision approach radar RP-5G, the maximum detection ranges were determined, which amounted to 380, 2730, 4480 and 14350 m for UAVs with an RCS of 0.01, 0.05, 0.1 and 0.5 m², respectively. The length of the blind spots of the RP-5G was 4620, 2270, 1019 m for UAVs with an RCS of 0.01, 0.05, 0.1 m², respectively. Under the vehicle RCS of 0.5 m² and greater, no blind spots are observed.

Conclusion. Analytical expressions for calculating the maximum detection range and blind spots were obtained. The results can be used when assessing specific features of UAV observation in the aerodrome area (landing sector). Standard precision approach radar systems can be used when surveying UAVs with an RCS greater than 0.5 m². For UAVs with an RCS of 0.1...0.5 m², modernized precision approach radar systems with an increased probing pulse energy should be implemented.

Introduction. Light-emitting diode (LED) irradiation is widely used in various spheres of human activity, including agriculture. Due to the growing urban population and aggravating environmental situation, the problem of high-quality food provision is increasingly attracting research attention. In this context, it is important to develop energy-efficient optical systems for ensuring optimal irradiation conditions for accelerating the growth of various types of plants and improving the quality of products in autonomous agro-industrial complexes.

Aim. Determination of an optimal spectral radiation composition of a phytolamp consisting of LEDs based on AlGalnP (660 and 730 nm) and InGaN (440 nm), as well as phyto-LEDs (400. _ .800 nm), to stimulate the growth and development of tomato and carrot sprouts at the germination stage. Calculation of the LED optical power and photosynthetic photon flux density (PPFD).

Materials and methods. Experiments were carried out to study the influence of visible radiation of different quality and quantity on the development parameters of carrot and tomato seeds, including germination energy, the appearance of cotyledon and primary leaves, seed germination, average hypocotyl and root length. Optimal spectral composition and radiation power parameters ensuring effective growth of plants were determined.

Results. Additional 660-nm irradiation of tomato sprouts at the germination stage was shown to exhibit a positive effect on germination, average sprout length and root development. The best results of carrot germination and development were achieved when irradiated with short-wavelength light (PPFD 243 µmol∙s^–1∙m^–2). Irradiation of ~ 170 µmol∙s^–1∙m^–2 blue and 86 µmol∙s^–1∙m^–2 red light was found to be effective for enhancing carrot cultivation.

Conclusion. The developed irradiation schemes can be used to vary the spectral radiation composition and PPFD at different stages of crop growth and development, thereby increasing yields and reducing energy costs. In the future, this technology can be used in space research, where high energy efficiency is fundamental.

Introduction. In view of growing environmental concerns, innovative solutions to ensure electrical energy supply to various devices and systems are required. As a result, renewable energy sources, including those based on solar energy, are attracting much attention. In this context, the development of a Wi-Fi router powered by modern photovoltaic converters seems to be a relevant research task.

Aim. Development of a Wi-Fi router powered by modern photovoltaic converters.

Materials and methods. The proposed system was developed on the basis of a Wi-Fi router YF360-H and a photovoltaic cell HVL-105/O.

Results. Calculations of the developed photovoltaic system were performed; volt-ampere and watt-ampere characteristics of the solar panel were investigated. The solar panel power supply circuit was developed, with the conversion efficiency in the working area achieving 90 %. The capacity of the external battery ensuring the system's autonomous operation for 7 days was determined. A modeling experiment in the MATLAB environment demonstrated the high efficiency of the developed system.

Conclusion. According to the conducted calculations, a HVL-105/O photovoltaic cell can be used to power a Wi-Fi router YF360-H under the weather conditions considered most unfavorable for solar cells.

Introduction. Materials exhibiting high dielectric permittivity are relevant for use in modern ultrahigh-frequency electronics. Among them, ferroelectrics with high dielectric nonlinearity present particular interest. The electrical strength of ferroelectric materials can be increased using modern composite structures based on mixing ferroelectries and linear dielectrics - materials exhibiting simultaneously low dielectric permittivity and high electrical strength. This approach provides for the opportunity of creating new multicomponent materials with previously unattainable properties and adjusting their component composition, inclusion size and electrical properties across a wide range. In this work, on the basis of porous potassium-iron-silicate glass (KFS) obtained by ion exchange, glass-ceramic materials containing barium titanate were synthesized for use at ultrahigh frequencies.

Aim. Production of glass composites by low-temperature sintering of pre-synthesized BaTiO₃ (BTO) and potassium-iron-silicate glass, as well as characterization of their structural and electrical properties at ultrahigh frequencies (microwave).

Materials and methods. The crystal structure and phase composition of the obtained films were studied by X-ray diffraction using a DRON-6 diffractometer by the emission spectral line CuK_α1 (λ = 1.5406 Å). The dielectric permittivity (ε) of microwave samples was evaluated by the Nicholson-Ross method at room temperature using an Agilent E4980A LCR-meter.

Results. According to X-ray diffraction analysis, the synthesized samples are a mixture of KFS glass, ferroelectric BaTiO₃ and dielectric barium polytitanates; the ratio of the latter determines the electrical properties of the composites. Depending on the content of barium titanate, the studied samples demonstrate a dielectric constant from 50 to 270 at a dielectric loss level of 0.1...0.02. The samples subjected to annealing in an oxygen medium showed an increase in dielectric permittivity by 10.25 % and an increase in controllability with a decrease in dielectric losses by an average of two times.

Conclusion. The composite composition of 70 wt % BTO /30 wt % KFS was found to be the most promising in terms of structural and electrical properties. This composite showed an increase in dielectric permittivity by 25 % and a significant increase in nonlinearity, at the same time as reducing losses by more than two times as a result of annealing in an oxygen medium.

Introduction. Lung cancer is one of the most critical diseases globally, with more than 1.6 million new cases registered every year. Early detection of lung cancer is essential; therefore, particular attention should be paid to the development of effective diagnostic and therapeutic procedures. Computer processing of CT scans in the course of lung cancer diagnostics involves the following stages: medical image acquisition, pre-processing of medical images, segmentation, and false-positive reduction. Since segmentation is an essential stage in the process of medical image analysis, the development of novel segmentation approaches is attracting much research interest. Model-based segmentation approaches have recently gained in popularity, largely due to their potential to restore lost information.

Aim. To apply a texture appearance model for the segmentation of pulmonary nodules on computed tomography of the chest.

Materials and methods. A novel model-based Texture Appearance Model (TAM) is proposed for precise and effective segmentation of all sorts of nodule regions. We taught the TAM for segmentation of a lung nodule in lung CT images using a combination of extracted texture characteristics from CT scans and Texture Representation of Image (TRI).

Results. The results of applying the described TAM method to normal and noisy CT images are presented and compared to those obtained using the Region Growing and Active Contour algorithms, as well as the combination of Active Contour and Watershed algorithms. The TAM was tested in 85 nodules from a dataset, yielding an average dice similarity coefficient (DSC) of 84.75 percent.

Conclusion. A novel method for segmenting nodules in the lung, which is capable of segmenting all forms of nodules with excellent accuracy, is proposed. This model-based technique, when used with the active loop algorithm, can enhance accuracy and decrease false positives by selecting the initial mask. The precision, dice, accuracy, and specificity of lung nodule segmentation on a normal CT scan are 85.5, 85, 96, and 98, which levels are superior to those produced by the Active Contour, Region Growing and the combination of Active Contour and Watershed algorithms.