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The article discusses the issues of forest canopy research. A solution to the problem of monitoring the state of the stand by probing with a high-frequency electromagnetic wave is proposed. This solution will find application in taxation and other Forestwork. В статье рассмотрены вопросы исследования лесного полога. Предложено решение проблемы мониторинга состояния древостоя путем зондирования электромагнитной волной высокой частоты. Данное решение найдет применение в таксации и других лесохозяйственных работах.

A method of long-term combined accumulation of the reflected signal is justified, which provides for its division into disjoint subsets, coherent accumulation in subsets using one of the fast algorithms and subsequent incoherent accumulation of the squares of the modules of the results of processing the subsets. A distinctive method’s feature is the use with incoherent accumulation of maxima of the squares of the moduli of the coherent processing results, that are selected from the range / radial velocity regions in accordance with a given hypothesis about the minimum and maximum values of the target radial velocity and the radial acceleration detection channel setting.The efficiency of the method was confirmed by simulation modeling. Using the theories of ordinal statistics and the method of moments, a method for calculating the probability of correct detection is developed. Estimates of processing losses are made in comparison with coherent and incoherent accumulation algorithms for a signal reflected from a point target, for the case when there is no range and frequency migration. Estimates for the required number of receiver channels are given.

The features of the implementation of the algorithm for the synthesis of detail radar images for an aperture synthesis radar using the built-in functions of the Cuda library are presented. The estimation of computational complexity from the standpoint of the organization of parallel computing on Nvidia GPUs is given. The estimation of the real performance of radar synthesis is given, taking into account the volume and features of the placement of primary radar information.

Introduction. A radar image is an image obtained by remote sensing the earth's surface with a radar device. Radar images are characterized by background graininess caused by speckle noise, which should be filtered to improve the quality of radar images. The structure of speckle noise reduction filters often comprise one or more parameters to control the level of noise smoothing. The values of these parameters have to be selected experimentally. In works devoted to speckle noise filtering, the methods used for selecting filter paraments are rarely clarified.Aim. To present a methodology for selecting the parameters of multiplicative speckle noise filters on a radar image that are optimal in terms of the quality of the resulting image.Materials and methods. The article presents a method for determining the optimal parameters of speckle noise reduction filters. This method was applied to the most conventionally used filters. The search for optimal parameters and testing of the filters were carried out using a specially designed image, which contained the objects most frequently found on radar images. The structural similarity index (SSIM) metric was chosen as a metric that assesses the quality of filtration.Results. After determining the optimal (in terms of SSIM) parameters of speckle noise reduction filters, the filters were compared to select the best filters in terms of the quality of radar image processing. In addition, the operation of the filters under study was tested on images containing various types of objects, namely: large objects, small objects and sharp borders. Knowing which filter copes best with smoothing speckle noise in a particular area and what values of the variable parameters this requires, an optimal quality of radar images can be achieved. Filtering not only improves human perception of radar images, but also reduces the influence of speckle noise during their further processing (object detection, segmentation of areas, etc.).Conclusion. The proposed algorithm allowed optimal parameters for several speckle noise filters to be determined. The quality of filtration was assessed using an expert method (visually) by comparing images before and after filtration, differential images and one-dimensional image slices. The Frost filter and the anisotropic diffusion filter with optimal parameters showed the best processing quality according to the SSIM metric.

The article discusses the possibilities of estimating the states vectors of observation objects with the nonMarkovian approximation of the trajectories. The introduction discusses the problem consisting in the fact that the use of the approximation of the trajectory of the observed object by Markov processes in some cases can lead to a discrepancy between theory and practice. In the first section, we simulate the trajectories of observed objects when approximated by a Markovian process and indicate the limitations of this approach. It is proposed to use a multidimensional Gaussian distribution law for generating the trajectory of the observed object. In the second section, a study of the accuracy characteristics of a single-position angular-rangefinder radar and a three-position rangefinder radar are considered. Algorithms α-β, Kalman and nonlinear estimation are used in the modeling as estimation algorithms in these systems. The parameters and characteristics of the simulation are given. In the third part, the results of modeling the process of estimating the location of objects of observation with trajectories of movement approximated by non-Markov processes are presented. Modeling confirms the possibility of using submitted algorithms to estimate the trajectory of a smallsized object of observation, a trajectory model of which uses a multidimensional normal distribution law. It is pointed out that in several cases the filtering errors exceed the errors of a single measurement. This leads to the conclusion that further modification of the algorithms is necessary. In the final part, a recommendation is given on how to further reduce the estimation errors when using Kalman algorithms and nonlinear estimation.

Introduction. Synthetic aperture radars (SAR) are important components of aviation-based systems for remote sensing of the Earth. The current level of such systems allows simultaneous radar surveys in several frequency ranges. Such surveys require complexing of the images formed in each of the frequency channels, which task is yet to be resolved.Aim. To review the formation principles and methods for joint processing of images using space and aviation-based multi-band synthetic aperture radar systems.Materials and methods. The methodology of systems analysis, involving the integral stages of decomposition, analysis and synthesis, was used. Decomposition of integrating multi-band radar images was performed considering the effect of various factors on the characteristics of radar images in different frequency ranges. Such factors include the principles of radar imaging, issues of radar images of multi-band synthetic aperture radars with real characteristics, and complexing levels.Results. According to the classical systems approach, the results of review and analysis are corresponded by appropriate conclusions on the shortcomings of each decomposition element and the synthesis of a proposal for achieving the goal. It was shown that joint processing of multi-band radar images can be carried out at the levels of signals, pixels, features and solutions, as well as their aggregates. Each approach is characterised by its shortcomings, which impede implementation of full integration of multi-band radar images without loss of information, which is due to the absence of information redundancy of radar images, compared to, e.g., optical images.Conclusion. Recommendations on the application of a particular method and the synthesis of a system for radar complexing images based on the texture-fractal approach were formulated. Directions for further work meeting all the requirements for completeness, reliability and information content of remote sensing of the Earth were outlined.

Поступила: 18.07.2022. Принята в печать: 19.09.2022. Received: 18.07.2022. Accepted: 19.09.2022. Рассмотрены основные факторы, влияющие на эффективность автоматической системы распознавания объектов на радиолокационном изображении, полученном с помощью радиолокатора с синтезированной апертурой антенны. Разработан алгоритм кластеризации для выделения объектов на радиолокационном изображении. Приведены результаты применения алгоритма кластеризации радиолокационного изображения, позволяющего повысить вероятность правильного распознавания объектов. Приведен анализ эффективности применения алгоритма кластеризации в зависимости от порогового обнаружения. Разработана и приведена структура двухэтапной системы алгоритма автоматического распознавания объектов на радиолокационном изображении. The main factors influencing the efficiency of an automatic object recognition system in a radar image obtained with a synthetic aperture radar are considered A clustering algorithm of selecting objects on a radar image has been developed. The results of applying the radar image clustering algorithm, which makes it possible to increase the probability of correct recognition of objects, are presented. An analysis of the effectiveness of the application of the clustering algorithm depending on the threshold detection is given. The structure of the two-stage system of the algorithm of the automatic recognition of objects on a radar image has been developed and presented.

We obtained the analytical expressions for the mean square deviation of errors in estimating the angular coordinates of the target for quasi-optimal algorithms of processing the fluctuating signals in radar meters with a scanning multichannel receiving system under external interference. Analytical estimates are based on the construction and circulation of the Fisher information matrix with a joint estimation of the direction of arrival and power of the fluctuating reflected signal at the output of the isotropic receiving antenna and a parabolic approximation of the mean value of the decisive statistic in the vicinity of the target direction for the processing algorithm, which provides for an estimate of the average power of the reflected signal by the least square method. The research demonstrates the convergence of exact and approximate analytical estimates and the results of computer modeling. We present the results of studying the accuracy of determining the angular coordinates of the reflected signal for typical space-energy cases. It is shown that the estimation error of the angular coordinates of the reflected signal are unbiased, and at small intervals of the correlation of the reflected signal the probability density of estimation error of the target azimuth exhibits normal distribution. In case of large correlation intervals, the distribution significantly differs from normal and acquires a large positive kurtosis and asymmetry with their values depending on the angular differences of the interference source and the target. The obtained expressions can be used to evaluate the effectiveness of quasi-optimal radar meters in the conditions of external interference and in the complex modeling of radar facilities with such meters included.

This article discusses the application of complex methods for detecting, recognizing, distinguishing borders and measuring various parameters of noisy, low-contrast, difficult-to-see images of space, air or ground objects. The problem of detecting, recognizing, distinguishing and measuring parameters of objects images (space or air objects, aircraft, ship, ground transport, people, coasts, etc.) is still among the very complex, completely unsolved radio engineering and telecommunications (“connected”) tasks. Currently, infrared (IR) direction finding, optical (laser location) direction finding and radar are used to detect, recognize, distinguish boundaries and measure the parameters of unknown objects against the background of external natural or artificial interference and noise. These methods have their own advantages and disadvantages, which do not always coincide. Therefore, it is of theoretical and practical interest to use them jointly, multifunctionally, or integrationally to identify objects against the background of external natural or deliberate interference and noise. When applying multifunctional methods for detecting, recognizing, distinguishing borders and measuring parameters of noisy, low-contrast images of objects against the background of external natural or artificial interference and noise. Digital processing of objects is mainly used now, which can be defined as a process during which an image is: modified to obtain a new one, which will be more convenient for research by a computer, or by the human eye; it is transformed into a certain set of characteristics and parameters visible and related to the observation area that are automatically analyzed by the computer, or directly presented to a person, taking into account pre-established criteria for developing a final conclusion about the studied object. Typically, the result of digital processing of the received signals is a new image that can be easily converted to analog form and directly observed on a computer display.

Introduction. A hardware basis of modern Advanced Driver Assistance Systems (ADAS) consists of millimeterrange radars, characterized by a relatively short range (meters – tens of meters). At the same time, improving of traffic safety requires to increase the range at least to several hundred meters. The one way to achieve such values is to increase wavelength of a probing signal, to use the centimeter range of wavelengths, for example. The paper represents a detailed description of main steps of signal processing algorithm in the model of the ADAS low-power centimeter range radar, which provides fast-moving objects speed and range definition.Aim. Development of an algorithm for estimating the range and the speed of targets by an autocorrelation radar with a wide-band continuous linear frequency modulation (linear FM) signal in order to increase the rate of the ADAS system estimates formation.Materials and methods. The proposed algorithm is based on the methods of primary and secondary digital processing of radar signals. The model of a centimeter-range autocorrelation radar with a broadband continuous linear FM probing signal was used for practical researches. MATLAB software was used to process the received signal samples.Results. The algorithm has been developed to determine the speed and the range of fast-moving objects in conditions when their movement during the evaluation interval significantly exceeds the radar range resolution. The use of simplified Kalman filtering for inter-period secondary signal processing allowed to increase significantly the stability of the algorithm. In a full-scale experiment using the low-power radar model with continuous radiation of the centimeter range, it was shown that a stable assessment of a real car speed and range was provided at a distance of at least about one kilometer.Conclusion. The results of the field experiment make it possible to draw conclusions that the proposed algorithm is highly robust even in the absence of inter-period secondary processing. Its usage allows one to improve the stability of the algorithm without considerable additional computational costs. It is possible because near-linear dynamics of the observation object and of the radar carrier makes it sufficient to use a simplified implementation of Kalman filter in the form α-β-algorithm.

The article presents the tasks, characteristic features, tactical and technical characteristics, the possible location and scope of the near-airfield meteorological radar complex. The analysis is made of the comparison of meteorological radar data from the near-airfield meteorological radar complex with reliable sources of meteorological information obtained during preliminary, acceptance, certification tests. The features of carrying out during the validation tests of meteorological radar data of the near-airfield meteorological radar complex are described, namely: dangerous meteorological phenomena (showers of different intensities, thunderstorms with a probability of 30-70%, 71-90%, > 90%, hail of varying degrees of intensity, squall of different intensities), velocity and direction of movement of cloud formations, vector velocity field. Examples of comparing the data of the near-airfield meteorological radar complex with data from a priori reliable sources of information are shown in the form of maps, graphs and tables. It is shown that the data of the near-airfield meteorological radar complex were obtained during testing and certification covering the warm and cold periods of the year, the sample size is statistically significant (except for the sample to assess the vector velocity field from data of aircraft and radar due to the spatial-temporal features comparing data from the two indicated information sources). It was established that the near-airfield meteorological radar complex provides acceptable in accordance with the requirements the construction quality of meteorological phenomena maps, the vector velocity field and the estimation of the cloud formations movement vector. The article illustrates the results of the statistical analysis of the data of the near-airfield meteorological radar complex, obtained personally by the author of the article. Analysis of meteorological data of the near-airfield meteorological radar complex was carried out with the aim of further exploitation of the near-airfield meteorological radar complex.

Introduction. Remote monitoring of layered underlying surfaces is an urgent task. To assess the performance of new algorithms for processing the radar signal reflected from the surfaces, full-scale tests are required. As their carrying out demands big expenses, simulation modeling is actual. There are many methods of estimating an electromagnetic field (EMF) scattered by the earth's surface. However, there are no proven methods and algorithms for engineering calculation of the reflected radio signal in the conditions of this problem.Aim. The aim is to develop and to verify a software model to simulate the reflected multilayer extended structure of the radio signal received on board the aircraft.Materials and methods. The core of the model was based on high-frequency electrodynamics' methods, which allowed rapid calculation for large areas of targets with any number of layers. Simulation was produced using the MATLAB software package. The developed simulation model represented the result in the form of the normalized radar cross-section (RCS) of the multilayer structure. Since the layered structure had rough boundaries, the model provided triangulation of the boundaries of the volume-distributed object. The resulting EMF was calculated using the superposition principle. Each partial EMF value on the facet was calculated taking into account the phase and the polarization of the locally incident EMF.Results. In the paper the comparison of simulation results with theoretical calculations for the normalized RCS of a two-layer structure (difference is less than 10 percent) was presented. Verification for the coefficient of variation of the envelope of the reflected radio signal from the depth of groundwater (critical error was 7 percent) was performed. RCS modeling of the absorbing layer with different degrees of roughness of the layer boundaries was carried out. The upper boundary roughness (for maximal height deviation 0.1 m) affected on specific EPR more than lower boundary. It manifested itself in decreasing of RCS down to 30 dB.Conclusion. The developed model is intended to reduce expenses for designing synthesis of subsurface imaging systems with comparison of scheme "model of device development – field tests – completion – etc". The model is designed to verify the new signal processing algorithms for subsurface radar.

Introduction. Modern air targets, particularly drones, are becoming less noticeable, while their manoeuvrability continues to improve. Trajectory processing algorithms have also been improved in order to provide for effective tracking of highly manoeuvring targets. The accuracy of filtering trajectory parameters is largely determined by the reliability of radar information. This has also required an enhanced role for strobe algorithms and the need to increase the effectiveness of strobe radar marks.Aim. To develop and investigate the efficiency of a trajectory strobe algorithm based on the target motion model in a high-speed coordinate system associated with the direction of the target motion and involving the formation of a strobe in the form of a truncated elliptical sector.Materials and methods. The study considered the target motion model in the body-fixed frame. This model was taken as the basis for new trajectory filtering algorithms based on Kalman filtering. Existing methods for strobing radar marks of the target were considered and a new approach based on filtering in the body-fixed frame proposed. The new algorithm assumes the formation of a strobe in the form of a truncated elliptical sector. This form corresponds to the most probable location of the marks of the tracked target. The effectiveness of the proposed solutions is confirmed by the results of mathematical modelling carried out using MATLAB.Results. The study produced analytical expressions for the motion model, recurrent filtering and strobe algorithm in the body-fixed frame. A comparative analysis of tracking effectiveness with the same volumes of the elliptical and proposed strobes was performed. It was established that the algorithm with strobe formation in the shape of a truncated elliptical sector provides for longer target tracking up to the time of the first loss of the mark for speed and highly manoeuvring targets, when compared to the elliptical strobe algorithm. In addition, the average duration of sector strobe tracking does not in practice depend on the initial speed of the target and provides greater accuracy for small measurement error values (less than 50 m) of the coordinates than in comparison with the elliptical one. Conclusion. The described results were achieved by the ability of the strobe in the body-fixed frame to adapt to the direction of motion and target manoeuvring, allowing high-quality target tracking within a larger speed range. Such strobe formation will also reduce the likelihood of skip-ping radar marks from the tracked target and will reduce the number of false marks belonging to other trajectories inside the strobe.

Using the method of synthesis of the information model at the automated workstation of the air traffic control dispatcher, a fragment of the user interface at the automated workstation of the radar control dispatcher of the Minsk district control center was synthesized, which allows to simulate the stages of the dispatcher's activity in the automated air traffic control system at the modern level of air traffic intensity. The verification of the adequacy and effectiveness of the synthesized user interface fragment was carried out directly with the participation of experts and specialists with experience in such systems. The adequacy of the synthesized user interface fragment was evaluated using a known consent criterion. The evaluation of the efficiency of the synthesized fragment of the user interface of the environment at the dispatcher's automated workstation was carried out under conditions of high air traffic intensity, which force the radar control dispatcher to control in critical mode of operation. Shows the advantage of a synthesized user interface fragment over an existing user interface in terms of time and accuracy. In general, the synthesized user interface fragment exceeds the existing one by about thirty percent. The synthesized user interface fragment noted the more stable activities of the subjects, as well as their better learning capability compared to the existing user interface. The developed experiment scheme allows to carry out research of engineering and psychological factors in human-machine systems of special purpose, including analysis of user interfaces at automated workstations of dispatching personnel in existing automated systems of air traffic control for their assessment and further improvement.

The upcoming transition to a new generation of the elements in the ATC system - AZN-B - has set a number of tasks related to confirming the integrity of the data received, and determining their accuracy characteristics. Radar surveillance systems which are used up to now have established a good reputation and the matter of succession is naturally associated with the comparison of these two recording systems data. Discrepancies (differences) in the AZN-B registrations and radar data are an additional source of information related to reliability and accuracy of their measurements. The problem lies in the method of information extraction. The article analyzes the stable features of discrepancy distribution (histograms) probability obtained in the "Air Navigation Research and Development Institute" branch of GosNII GA by analyzing the observations of aircraft operations in Moscow region. The presence of asymmetry in these histograms is supposed to be interpreted as the presence of uncompensated latency in the transmission of data from AZN-B, which is typical for a certain portion of aircraft in the airspace of Russia. The emphasis on the "territorial affiliation" of the effect is due to the fact that we don’t have any information about the works abroad devoted to the phenomenon under discussion. In accordance with the hypothesis stated, a mathematical model of the measurement procedure with the following parameters to be estimated was constructed: the average value of the uncompensated delay and the expected share of aircraft, characterized by this defect. The values of the sought-for parameters were discovered according to the condition of minimum "distance" between the experimental histogram and the corresponding model analytical dependence. The estimates made revealed that about 30% of the aircraft, out of the total observed number, report their coordinates with an additional error of 75 m. at an average.

Monitoring technologies are rapidly developing at present and allow to extract and use non-coordinate information about objects. Noncoordinate information is the information about the type and properties of an object under study. Remote sensing is the main method of solving monitoring problems where special positioning belongs to the radar methods, based on space-time processing of signals and, in particular, on methods of radio polarimetry. It is necessary to have information about the surface in order to solve the monitoring task. The slightest changes in the electrical and physical properties of such areas as salinity, humidity, soil composition, etc. will lead to a change in the basic electrodynamics of the surface, notably its complex dielectric permittivity. The article demonstrates the precise solutions to the problems of radio-waves reflection from a layered surface with various laws of changes of the complex permittivity  in depth. Media with exponential and quadratic laws of variation  for arbitrary angles of incidence of the radio wave on the surface are considered. Precise decision is obtained for layered media with the law of change in the complex permittivity the polynomial and linear characteristics. A similar problem for the parabolic layer is considered separately. The detailed analysis of radio waves reflection from the medium with a matching layer is carried out. The nature of the electromagnetic field inside the transition layer is studied in detail. The article is illustrated by the graphs showing the dependences of an electromagnetic wave reflection coefficient on the layered medium with linear and exponential laws of variation of the complex dielectric constant over depth.

Introduction. The modern approach for ensuring marine activities of necessary quality related to the assessment of current information on the state of the ocean environment in Russia is clearly insufficient. The development of operational methods and instruments of observation, as well as the assessment of the state of the ocean and its forecast naturally determine such an approach. Therefore, the development of the concept, tools and methods of obtaining data is an urgent task of the operational Oceanography formation.Objective. The objective of the paper is to con-sider the concept of ocean surface monitoring using short-wave surface wave radar.Methods and materials. The paper presents a number of specific Oceanologic examples that require operational monitoring of the state of coastal waters of the oceans and individual regions. Also, it describes observational systems used in other countries. The paper pays special attention for the development of radar sensing of surface waters, carried out in our country occasionally. The resonant nature of the reflections gives the opportunity to obtain maps of high-precision measurements of surface currents and wave characteristics on the long-range area in real time. The paper notes difficulties of the experiments implementation and the results interpretation, shows the insistent issues for the establishment of the ocean surface operational monitoring, and gives the approaches for solvation of the existing problems. The paper formulates the main task of the world ocean parameters forecast for ensuring of the sea transport safety from natural and anthropogenic threats, as well as formulates the problems solution of effective nature management.Results. The paper shows that the optimal means of natural data acquisition is the creation of an observation network of coastal HF radars, which enables to assess surface currents and wave characteristics, as well as to solve the problem of monitoring. It is Important to develop an adequate coastal model and correlate its parameters with experimental data. The adaptive modeling and monitoring by modern technical means can overcome inadequacy of physical models to specific natural conditions can.Conclusion. By assimilation in hydrodynamic and wave models, these data become applicable in spatial mapping of hydrophysical inhomogeneities of the water layer, sound velocity, and underwater acoustic noise.

Aerodrome-enroute surveillance radar systems (ARSR) of civil aviation are designed for detection of aerial objects and determination of their range and movement parameters. Meanwhile, the reflector-type antennas are still the main type of_used antenna systems. Radars (ARSR) have, as a rule, antennas with a bidirectional beam, structurally reflector-type antenna is made in the form of a truss welded structure. The use of active phased antenna arrays (APAR) is a promising direction of radars (ARSR) development. Radars (ARSR) based on the phased antenna arrays can significantly improve such critical tactical and technical criteria as: the accuracy of the coordinates determination, the number of simultaneously followed targets. However, the use of APAR does not solve one of the main problems - the presence of a support-rotary device in the radar (ARSR). The principal necessity of a support-rotary device leads to the need of the use of movable joints of feeder lines, which, with a significant number of antenna elements used in the PAR, significantly reduces the potential time before failure. It seems promising to use in the radar antenna systems based on several stationary multi-beam dual-reflector antennas made by axially asymmetric scheme. Methodology of estimation of aberrations of a dual-reflector sensimetrics antenna based on a polynomial expansion of the eikonal function in the plane of the aperture of the main reflector is proposed in the article. Analytical expressions of the functions of display and rotation of the scanning plane of a dual-reflector axially asymmetric antenna with arbitrary parameters, designed based on clippings from centrally symmetric surfaces of rotation of the second order, are obtained. It is shown that the aplanatic antennas lose their scanning features during the transition to the axially asymmetric variant.

The disadvantage of (RLI) radar images obtained with a single-channel radar station is the presence of speckle that leads to intensity flashes increasing the number of false alarms when detecting point targets. Therefore, the detection and target distinguishing by their reflective capability (using the energy characteristics of the signal) is not effective enough. In polarimetric radar stations the formation of each image element is carried out by the output signals of four receiving channels. Joint processing of these signals allows minimizing speckle without reducing the resolution capability. The paper presents the results of the computer simulation of the suppression methods of the image speckle obtained in the polarized radar stations with the synthesized antenna aperture. The first one uses the norm of the backscattering matrix as a parameter of the intensity of the reflected signal resolution from the i-th element. The incoherent addition of the intensities obtained by sequential overview of the space with several rays is carried out in the second one. Both of these methods can be applied together. The block diagram of such processing for one strip of range is given. The computer simulation of the three-rayed suppression method of the image speckle obtained in the radar stations with the synthesized antenna aperture is carried out. As a model of the reflecting surface a random diffraction grating formed by a set of independent reflectors located at the nodes of a regular rectangular grid with a step of 1 m is chosen. In this connection the image of the grating is formed as an incoherent sum of three images obtained at different angles. The results show that the speckle effect reduces even at angular changes of the order of degree units.

Nowadays the interest in search of ways of improving the efficiency of small radar cross-section aerial objects detection and localization rises against the background of widespread use of light and unmanned aerial vehi-cles. As a result, researchers pay attention to radar systems (RS) with continuous linear frequency modulation (linear FM) signal. The use of such signals gives the measurable opportunity to reduce radar system peak-speech power and to cut the cost and weightsize parameters of the RS. The paper observes low-power ground based radar implementation prospects for purposes of detection and estimation of motion rates of small-sized aerial objects. The proposed algorithm of radar signals processing enables to simplify the detection of such tar-gets. The paper reveals the structure and defines the steps of the algorithm. The fundamental for the algorithm under consideration is the method of the range-Doppler image composition of the scanned area using digital signal processing. The paper presents the results of the algorithm operation in the low-power RS of C-band radar, obtained by processing of quadrotor echo-signals during the real experiment. The results show successful solvation of the applied problem of detection and tracking on the small-sized aerial object with the radar cross-section equal to less than 0.5 m2 and the spectrum of secondary radiation characterized by the expressed multimodality. The results of the experiment validate the application of the algorithm and demonstrate the possibility of the algorithm implementation in design of portable RS and automated target acquisition centers for detecting and tracking of the small-sized aerial targets (both, single as multi agent) with the information display on operator control panel.

ObjectivesThe aim of the study is to develop a methodology for identifyingaircraft by the deflections of an electromagnetic radar beam by a heated jet engine. MethodsAtoms of the crystal lattice of the metallic parts of the operating jet engine will be in a state of chaotic Brownian motion due to heating. The electromagnetic beam, falling on these atoms, will change its frequency in accordance with the Doppler effect, by means of which the spectral electromagnetic radiation component will expand in direct proportion to the magnitude of the engine temperature. When determining the width of the spectral line of the direction-finding radio emission, it is possible to accurately identify the temperature of the aircraft in order to avoid false targets.ResultsWhen locating aircraft having a working jet engine, it is possible not only to determine the coordinates of the target, but also to identify the heated engine. Due to the use of high-precision methods for identifying heated sections, the direction-finding targets may be classified, the spatial orientation of both the aircraft itself and its control planes to be determinedand the direction of the thrust vector control of the jet engine calculated.ConclusionThe application of an innovative technique for direction-finding air targets will allow the radar targets to be identified with high accuracy against the background of active and passive interferences. In addition, when analysing the information on the magnitude and direction of the jet engine thrust and the position of the aircraft controls, it is possible to determine not only the coordinates of the direction-finding object, but also to proactively identify the manoeuvres to be performed.

Поступила : 01.11.2020. Принята в печать : 23.11.2020. Received: 01.11.2020. Accepted: 23.11.2020. Рассматриваются и сравниваются параметры антенных систем радиолокаторов, построенных по традиционной схеме с фазовращателями как в антенной решетке передатчика, так и в антенной решетке приемника с радиолокатором, в котором обработка сигнала выполняется только на приемной стороне. Во втором случае на излучающую систему передатчика накладывается дополнительное требование ортогональности излучаемых сигналов. Сравниваются характеристики радиолокатора с тремя передающими антеннами и четырьмя приемными. Рассматриваются два варианта формирования виртуальной антенной системы. В первом случае анализируется излучение линейной регулярной антенной решетки, во втором – прореженной, но с тем же числом излучателей. Показано, что во втором случае можно реализовать радар с лучшим угловым разрешением. Рассмотрены особенности применения радаров в качестве сенсоров систем безопасности автомобиля с широкоугольным обзором. Отмечена возможность ложного захвата цели. Предложен способ однозначной пеленгации. The parameters of radar antenna systems constructed according to the traditional scheme with phase shifters inserted both in the transmitting and receiving antenna array with the radar in which signal processing is performed only on the receiving side are considered and compared in the paper. In the second case, an additional requirement of orthogonality of the radiated signals is imposed on the radiating system of the transmitter. The characteristics of the radar with three transmitters and four receivers are compared. Two variants of forming a virtual antenna array are considered. In the first case, the radiation of the linear regular antenna array is analyzed, in the second case the thinned one, but with the same number of emitters. We demonstrate that in the second case, it is possible to implement the radar with a better angular resolution. The features of using the radar as a short-range radar for vehicle security systems with a wide-angle view are elaborated. The possibility of false capture of the target is noted. The authors of the research suggest the unambiguous direction finding method. Работа выполнена при финансовой поддержке Министерства науки и высшего образования Российской Федерации в рамках соглашения № 075-11-2019-052 от 13.12.2019 с Научно-производственным объединением автоматики имени академика Н.А. Семихатова (АО «НПО автоматики») по комплексному проекту «Создание высокотехнологичного производства высокочастотного радара, предназначенного для использования в составе интеллектуальных систем помощи водителю, систем автоматического управления беспилотных транспортных средств и систем интеллектуального земледелия» при участии ФГАОУ ВО «Уральский федеральный университет имени первого Президента России Б.Н. Ельцина» (ФГАОУ ВО «УрФУ») в части выполнения научно-исследовательских, опытно-конструкторских и технологических работ. This work was financially supported by the Ministry of Science and Higher Education of the Russian Federation under agreement No. 075-11-2019-052 dated December 13, 2019 with the Scientific and Production Association of automatics named after academician N.A.Semikhatov in the complex project “Creation of a high-tech production of a high-frequency radar intended to be used as a part of intelligent driver assistance systems, automatic control systems for unmanned vehicles and intelligent farming systems” with the participation of the Ural Federal University named after the First President of Russia B.N. Yeltsin in terms of the implementation of research, development and technological work.

At present, multilateration systems are becoming increasingly important in air traffic control. This is due to their significant advantages in compare with secondary surveillance radar complexes. This article solves the problem of synthesizing an algorithm for object location estimation for multilateration system operating in passive mode. The synthesized algorithm is a combination of a procedure, the result of which is a rough estimate of the observed object coordinates, and an iterative algorithm specifying the resulting solution. The rough estimate is the result of solving a linear system of equations. The iterative refinement procedure is based on the linearization of the observational equations and does not require a large number of iterations. The paper provides a comparative statistical analysis of the proposed algorithm and the known Bancroft algorithm. For an objective analysis of two algorithms, the paper derives the Cramer-Rao boundary for the correlation matrix of estimates of the observed object coordinates, which makes it possible to determine the potential accuracy of the solution of the problem. It is shown that both algorithms allow obtaining estimates, the accuracy of which is close to the potentially achievable accuracy of the object location estimate. In contrast to the Bancroft algorithm, the rough estimate of the object location is unambiguous. This virtue reduces the total amount of computations during the algorithm implementation and reduces the probability of anomalous errors.

Often, the monitoring systems solution of remote sensing problems, recognition (classification, discrimination) of radar objects using radio polarimetry methods is required in real time mode with the display of the current information on the radar monitor. Monitoring systems can be either stationary (more often terrestrial) or mobile (based on various transport vehicles). When designing such systems, along with ensuring the required speed and performance of the computer, it is also important to ensure the unification of the units and assemblies, the reduction of weight and size characteristics, simplification of the tuning, increase of the operational reliability. In this case, the use of blocks of digital information processing is required. When digitally processing polarized signals, it is necessary to convert the input analog signal to digital form, i.e. to sampled by time and frequency and perform level quantization. The peculiarities of the discretization of the radar polarized signal over time are considered in the article. Analytical expressions for the input polarized signal are derived with considering the geometric parameters of the polarization ellipse. Formulas are given for the in-phase and quadrature components of the polarized signal, for a complex signal envelope. It is alleged that quadrature processing of the polarized signal leads to a decrease in the requirements for analog-to-digital conversion chips due to a significant reduction in the sampling frequency. After the transformations presented in the article, electronic components, which are already in production by Russian companies in the radio electronic industry, can be used in monitoring systems. The transformations of a polarized signal in the time domain described in the article lead to certain transformations in the frequency domain. We are talking about converting the two-side signal spectrum into a one-side spectrum with its transfer to the video frequency region. Such a conversion helps to reduce the sampling rate from gigahertz to megahertz. Analytic expressions in the time domain are accompanied in the article by a graphic interpretation of the signal spectra in the frequency domain. A scheme for demodulating the in-phase and quadrature components of the polarized signal is given. Functional features of filtering units in the scheme are described, the attention of the designers of the digital signal processing systems to the requirements of the Kotel'nikov's sampling theorem is emphasized.

Source at https://doi.org/10.21443/1560-9278-2018-21-1-170-181. Licensed CC BY 3.0. Results of observations of variations of temperature, electron concentration and total electron content of the high-latitude region of the ionosphere during its modification by powerful short radio waves of the heating complex EISCAT/Heating (Tromsø, Norway) according to signals of the GLONASS satellites and the incoherent scattering UHF EISCAT radar (Tromsø, Norway) have been provided. The geometry of passes of the GLONASS and GPS satellites for operating conditions of the heating complex in Tromsø has been considered. It has been shown that during the experiments on the EISCAT/Heating complex for the study of the modified structure of the high-latitude ionosphere it is more convenient to use the GLONASS satellites. Parameters of orbits of these satellites allow researching changes of total electron content in the direction along the geomagnetic field line at the place of observation. It has been shown that during heating of the ionosphere by powerful short radio waves its structure is becoming an irregular one. Operation of the heating complex in the mode "switched on – switched off" has caused appearance of wavy variations of total electron content with the periods close to the heating period. The main features of behavior of the total electron content in the case of the continuous heating of the ionosphere in the direction of the magnetic zenith according to the GLONASS satellite are: reduction of total electron content in the central zone of the antenna diagram, i.e. in the direction of the magnetic zenith, and presence of the increased values of total electron content at the edges of the heating zone. According to the incoherent scattering radar the heating of the ionosphere by the powerful short radio wave has created the region of the increased electron temperature and electron concentration along the direction of the magnetic zenith. The behavior of total electron content according to the GLONASS satellite and the radar of incoherent scattering in many respects corresponds each other except the central part. Reasons of the mismatches have been considered. Представлены результаты наблюдений изменения температуры, электронной концентрации и полного электронного содержания высокоширотной области ионосферы во время ее модификации мощным коротковолновым радиоизлучением нагревного комплекса EISCAT/Heating (Тромсё, Норвегия) по данным сигналов спутников ГЛОНАСС и радара некогерентного рассеяния УВЧ ЕИСКАТ (Тромсё, Норвегия). Рассмотрена геометрия пролетов спутников ГЛОНАСС и GPS для условий работы нагревного комплекса в Тромсё. Показано, что во время экспериментов на комплексе EISCAT/Heating для изучения модифицированной структуры высокоширотной ионосферы удобнее использовать спутники ГЛОНАСС. Параметры орбит этих спутников позволяют исследовать изменения полного электронного содержания в направлении вдоль геомагнитной силовой линии в месте наблюдения. Показано, что во время нагрева ионосферы мощной коротковолновой радиоволной ее структура приобретает неоднородный характер. Работа нагревного комплекса в режиме "включено – выключено" вызывает появление волнообразных вариаций полного электронного содержания с периодом, близким к периоду нагрева. Основными особенностями поведения полного электронного содержания при непрерывном нагреве ионосферы в направлении магнитного зенита по данным спутника ГЛОНАСС явились уменьшение полного электронного содержания в центральной зоне диаграммы направленности антенны нагревного комплекса, т. е. в направлении магнитного зенита, и присутствие повышенных значений полного электронного содержания на краях зоны нагрева. По данным радара некогерентного рассеяния во время нагрева ионосферы вблизи направления на магнитный зенит формируется область повышенной электронной температуры и электронной концентрации. Поведение полного электронного содержания по данным спутника ГЛОНАСС и радара некогерентного рассеяния во многом соответствует друг другу, кроме этой области. Высказываются предположения о причинах такого несоответствия.

The basis of modern radar techniques is the direct use of radio-physical data on the power of backscattering. At the same time, the data volume received from the radar allows us to form new estimates and essentially specify classical ones. Significant steps have been made in this direction, using, for example, phase (Doppler) methods. The "modified Rayleigh model" used in radar meteorology to form a scattered field on rarefied medium particles is called the Kerr-Rice model. The main advantage of the Rayleigh model is its simplicity. But it itself contains a deep contradiction, consisting in its logical completion. Based on the statistics study of the first distribution in the rains of varying intensity the authors on a large statistical material have determined the fact of their not Rayleigh form and extreme stability of the latter in relation to natural changes of precipitation intensity. The first distribution is different from the theoretically expected one in the Kerr-Rice model, which makes it possible to use linear-logarithmic detection. It is concluded that the width and the mean of the spectrum of the same signal have the expected dynamics with respect to changes in precipitation intensity and dynamic processes in them. Tables with experimental data are presented. Two main distribution models are considered: lognormal and "logo-gamma-functional". It is concluded that, despite the absence of qualitative differences, the difference in the form of the distributions obtained with different equipment can be a natural consequence of significant discrepancies in the peak power and / or the width of the antenna pattern. The graphs of the first experimental distributions of envelope fluctuations on a linear and semi-logarithmic scale are presented.