Reliable design of radio relay links in complex propagation environments remains a significant challenge for mission-critical communication systems. This paper presents a propagation-aware link budget methodology that integrates terrain morphology, Fresnel zone clearance, atmospheric attenuation (including gaseous absorption and precipitation), and multipath propagation into a unified analytical framework in accordance with ITU-R recommendations. The main contribution lies in the systematic integration of multiple propagation mechanisms into a unified procedure for link availability estimation and propagation-aware radio-relay link assessment. A representative 15 GHz radio relay link between the Laz tunnel and the Ovcar site, designed for a capacity of 100 Mb/s within a TETRA system, is used as a case study for verification. Analytical calculations of received signal power, fade margin, and link availability are supported by simulation-based verification using Radio Mobile. Good agreement between analytical and simulation-based predictions was obtained, with a received signal level difference below 2 dB. Multipath propagation is identified as the dominant degradation mechanism, while rain attenuation has a secondary impact. The achieved link availability exceeds 99.99%, demonstrates practical applicability for the considered case study. Keywords: Radio relay link design, propagation-aware modeling, link budget analysis, multipath fading, TETRA communication systems
This paper presents a method for reconstructing the three-dimensional antenna radiation pattern from reduced sampled far-field measurements, thereby reducing the need for extensive mechanical probe scans. The sampling density is selected according to planar near-field measurement principles, enabling an initial plane-wave representation of the radiation field. An iterative interpolation procedure in the spectral domain is then used to recover the missing angular data while accounting for practical measurement resolution limits. The complete source code written in Julia programming language for the reconstruction algorithm is publicly available to support reproducibility and future research. Keywords: Antenna radiation, reconstruction algorithm, far-field pattern measurement, near-to-far field transformation
Accurate channel state information (CSI) is essential for multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems, yet fast time-varying channels pose significant prediction challenges. Traditional approaches fail under high mobility, while deep learning methods rely heavily on large labeled datasets, limiting generalization with scarce training data. Although large language models (LLMs) show promise, their massive parameter count hinders deployment on resource-constrained edge devices. This paper proposes a lightweight, end-to-end CSI prediction framework built upon a general LLM. A time-frequency dual-domain feature extraction module captures subcarrier correlations and temporal dynamics from historical CSI, overcoming single-domain limitations. The end-to-end design maps historical CSI directly to future states, avoiding error propagation inherent in explicit channel estimation. Parameter efficiency is achieved through low-rank adaptation (LoRA) combined with knowledge distillation from a pre-trained LLM, enabling effective few-shot learning at low computational cost. Simulations demonstrate that the proposed scheme delivers robust prediction accuracy across diverse mobility scenar-ios, maintains strong performance under limited training data, and exhibits zero-shot cross-scenario generalization, significantly outperforming both conventional and deep learning baselines in TDD and FDD modes. Keywords: Channel prediction, multiple-input multiple-output (MIMO), orthogonal frequency division multiplexing (OFDM), large language model (LLM), knowledge distillation, low-rank adaptation (LoRA)
Problem statement. The increasing attention to the electromagnetic environment of radioelectronic equipment (REE) in recent years is caused by the emergence of various types of electromagnetic interference. Among them, ultrashort pulses (USP) stand out, which are characterized by a fast rise time and large amplitude. Modal filters (MF) are proposed to protect against them. They decompose the USP into a sequence of pulses of lower amplitude due to the difference in the speed of modes in the line. MF are traditionally implemented in the form of strip structures, but a promising alternative is cable structures. Meanwhile, this requires a separate engineering approach and experimental verification. The purpose of the work is to develop a prototype MF based on a flat cable and measure its characteristics. Results. A methodology for prototyping and measuring MFs based on a flat cable is presented, and a prototype MF based on it is developed. The results of the MF measurements are compared with the results of computation-al experiments in the quasi-static and electrodynamic analysis systems. The nature of the dependences of the MF transmission coefficient modulus |S21| in the frequency band up to 2 GHz is similar for all types of analysis with a maximum deviation of 5.2 dB. The MF passband is within 75–310 MHz for measurements and two types of analysis. In the frequency range of 0–10 GHz, the measured modulus of the reflection coefficient |S11| of the MF does not exceed minus 7.4 dB. As a result, the developed MF (225 mm long) is capable of attenuating the influencing interference with a total duration of 200 ps (at the 0.5 level) by 7.03 times according to the measurement results, as well as by 4.3 and 7.45 times according to the simulation results in the quasi-static and electrodynamic analysis systems. Practical significance. The results of experimental studies expand the toolkit of engineers in-volved in the development and modification of protective devices (both based on flat cables and completely new ones). The developed MF is notable for its potential for practical application in protecting REE from USP in a variety of areas due to its compact size (225 mm) and low weight (up to 75 g), radiation resistance, reliability, and high protective characteristics.
Engineering solutions for determining the range to moving extended objects, as a rule, involve the use of a radar distance sensor. The main thing in this case is to obtain the minimum error in determining the distance to the object being localized. Note that digital signal processing introduces its own features in determining the methodological error of the distance sensor. The article proposes a solution based on the use of a method of local optimization of parameters of an arbitrary weight function used to smooth out measurement errors in distance sensors based on the principle of a frequency range finder. The methodological component of the error of the weight method is considered as one of the key factors determining the measurement accuracy. The purpose of the study is to optimize the parameters of the weight function, which makes it possible to ensure a minimum of the methodological error of the weight method for smoothing discreteness, and to assess the effect of noise from signal generation and processing equipment on the distance measurement result. Optimization of parameters significantly reduces measurement error, and the effect is the more pronounced, the larger the number of terms included in the decomposition of the weight function, that is, when its form is complicated. At short distances, the noise component of the measurement error has the same order of magnitude as the methodological error, while when the range increases, its value becomes much higher. The most pronounced effect of noise is observed in cases of using more complex weight functions. As the distance increases, the measurement error decreases. It has been shown that known weight functions provide the best results when measuring relatively long ranges. The effect of additive noise on the accuracy of determining the distance using the weight approach to reducing the sampling error was assessed. It has been found that at small measuring distances, the optimal weighting function coefficients provide effective suppression of the noise component. In the area of large distances, a monotonous decrease in noise error is observed, which, however, remains significantly higher than the methodological one. Analytical expression for measurement error variance obtained. The results obtained confirm the effectiveness and practical significance of optimizing the weight functions used in remote measurement systems based on frequency range finders. At the same time, the proposed solutions make it possible to determine the maximum permissible noise level that ensures the achievement of the required measurement accuracy in each specific case.
The investigated scientific and technical problem is related to the growing number of cyberattacks using malicious software (malware). Such attacks represent a complex security threat due to the wide range of possible destructive impacts affecting target computer systems. Malware is characterized by stealthy action through masking of malicious payloads or mimicry as legitimate software, which complicates their detection and neutralization. The research results consist of obtaining knowledge about the peculiarities of behavioral characteristics of malware and their influence on telemetry data, as well as expanding the methodological basis for security threat analysis through the use of indirect behavioral indicators. The validation results demonstrate the feasibility of using an architecture-invariant software solution that operates on reliable data from hardware components. Experimental studies confirmed the viability of the method: the best detection accuracy was 100%, classification accuracy was 90%. Due to the use of machine learning technology, the method can be retrained on new malware samples to maintain relevance.
Detection and tracking are essential to technical space monitoring systems, which must process substantial data volumes under stringent real-time constraints. For image-based systems, computational costs drop significantly when processing is confined to the frame region containing the object – the tracking window. This reduces tracking to determining how this window should shift in accordance with the object's motion. Solving the tracking problem requires detecting when a moving object enters the frame and establishing its coordinates and velocity. This calls for high-speed peripheral processing using computationally inexpensive yet sufficiently accurate features for characterizing dynamic objects. The image's phase-energy spectrum – a vector function combining energy and phase-frequency properties – offers a promising solution. For moving objects, the spectrum's most informative characteristic is its circulation. This study investigates whether phase-energy spectrum vector field circulation can support algorithms tracking objects that shift between frames. We derive an analytical expression for circulation along an arbitrary rectangular contour. The integration contours chosen are the boundaries of the phase plane's first and second quadrants, traversed positively. Specific expressions for circulation around these quadrants are provided. Results show zero circulation at two-dimensional period boundaries but non-zero values along quadrant boundaries. Absolute circulation values prove equal for both even and odd quadrants, justifying our focus on adjacent quadrant boundaries alone. Analysis reveals a relationship between circulation values over the selected contours and the object's frame position. Absolute circulation decreases as the object approaches the corresponding frame diagonal. This finding underpins an iterative algorithm for centering the tracking window – the frame subregion containing the object – between consecutive frames. We establish relations for the angle determining window displacement direction and demonstrate algorithm performance on real video footage. Computational cost estimates suggest the algorithm can run on specialized graphics hardware under demanding real-time operational requirements. These findings on vector field circulation generated by the image phase-energy spectrum can inform algorithm development for various observation systems: intelligent autonomous search, detection and tracking platforms, transportation analytics, industrial process control, and related applications.
Setting the task. The problem of detecting non-stationary active noise interference (ANI) in multi-channel radio systems with antenna arrays is considered. A multi-channel radio system with an antenna array is investigated. To implement an automatic canceller for active noise interference, the antenna system generates a main channel radiation pattern and several compensation channel antenna patterns, each differing in shape and overlapping the sidelobes of the main radiation pattern. The case in which the number of ANI is equal to the number of compensation channels is studied. The possibility of using the eigenvalues of the interchannel correlation matrix of the main and compensation channels as decision statistics is analyzed. Goal. To propose a method for detecting non-stationary ANI in multi-channel radio engineering systems with antenna arrays based on the analysis of the statistical properties of the eigenvalues of the sample interchannel correlation matrix. Results. The use of an interchannel correlation matrix of the main and compensation channels to detect non-stationary active noise interference is proposed. An analysis of the eigenvalues of the sampled interchannel correlation matrix is conducted. Decision statistics for detecting non-stationary active noise interference are obtained. It is shown that the optimal solution to the problem of detecting non-stationary active noise interference will consist of a comparison with a certain threshold of the minimum eigenvalue of the sampled interchannel correlation matrix. Numerical modeling was used to obtain detection characteristics (dependences of the probability of correctly detecting non-stationary active noise interference on the interference-to-noise ratio) and an analysis of the detection characteristics of non-stationary active noise interference is conducted depending on the mismatch angle (the angle by which the radiation pattern of the main channel deviates during the time of interference reception). Practical significance. In modern radio systems (e.g., radar stations), detecting non-stationary ANI is necessary for adapting jamming algorithms to non-stationary jamming conditions. The proposed method can be used in ANI defense systems to ensure detection of useful signals in non-stationary jamming environments.
The article analyzes the functioning of a multifunctional radar measurement system (MFRMS) in the radar mode of the synthesized aperture (SAR). The analysis of the characteristics of the MFRMS ensuring the operation of the MFRMS in the SAR mode is carried out, and proposals are made for equipping the existing complex, deployed according to the customers MFRMS, witch a set of equipment ensuring the operation of the MFRMS in the SAR mode, using thе scientific and technical reserve available at the enterpricse.
Problem statement. Microstrip lines (MSL) constructed using thick- or thin-film technology are traditionally used in the development of microwave devices for various electronic warfare (EW) components. The rapid development of EW systems necessitates the improvement of approaches to the implementation of microwave devices. One of the areas of development in the design of microwave devices is the use of technology based on multilayer low-temperature co-fired ceramics (LTCC). Changes in the manufacturing technology of microwave devices for EW systems necessitate the development of methods for ensuring optimal power transfer between microwave devices of planar design and those manufactured using LTCC technology in the form of symmetrical striplines (SSL), as well as the adaptation of measurement methods for the parameters of such microwave devices to account for the specific features of LTCC devices. Goal. To develop a transition from the MSL to the SSL, allowing for simplified installation of LTCC measured devices using standard tools and an improved methodology for measuring the S-parameters of microwave devices. Results. When using electrodynamic modeling of the transition from the MSL to the SSL was performed using a computer-aided design system. Based on an analysis of the characteristics of the electrodynamic model and optimization of the model's geometry parameters according to the criteria of maximizing the transmission coefficient and minimizing the reflection coefficient developed the transition from MSL to SSL which has the minimal impact on the characteristics of the measured LTCC device. The simulation results are confirmed by experimental measurements of bandpass filters (BPF) performed using LTCC technology. The methodology for measuring LTCC devices on a vector network analyzer (VNA) has been refined using test boards. Practical significance. The developed transition from MSL to SSL allows for the integration of LTCC microwave modules during the modernization of microwave devices with MSL. The LTCC measurement technique using microwave probe heads and test boards allow for measurement of upgraded devices on universal work places when using standard microwave measuring instruments.
The paper presents a Class E power amplifier (PA) characteristics analysis when amplifying radio frequency signals with a non-constant envelope. The relevance of the study proceeds from the use of various types of digital modulation to increase bit rate, which leads to signals peak-to-average power ratio (PAPR) growing. At the same time, it turns out that the specific for the Class E PA turn-on conditions of transistor with zero voltage switching (ZVS) and zero derivative voltage switching (ZDVS) at the drain-source terminals get broken, resulting in increased switching losses. An additional factor that can have a noticeable effect on the forming circuit capacitance overcharging, and consequently on Class E PA power efficiency is a sufficiently large increase in the output capacitance of the transistor when the supply terminal voltage is lowered. The paper proposes an analytical model of a Class E PA, which allows taking into account the above-mentioned effects, the adequacy being confirmed by simulation. It is shown that a decrease in the power efficiency of a Class E PA in the case of using the envelope elimination and restoration (EER) method for signals with a PAPR of up to 15 dB can amount to 12...14%.
Problem statement. Modern microwave devices are often complex multi-port structures incorporating lumped loads that require accurate modeling of scattering parameters, their optimization, and impedance matching within computer-aided design (CAD) systems, particularly using the Method of Moments (MoM). However, the specific aspects of computing scattering parameters via MoM –accounting for both active and passive ports as well as various types of lumped loads – are insufficiently addressed in the existing literature. This work fills that gap. Moreover, current methods for optimizing the complex load impedance to minimize reflections in microwave structures typically rely on a single basis function (BF) at the load edge, which restricts their applicability to problems with fine mesh discretization. To overcome this limitation, we propose an optimization algorithm based on the Sherman-Morrison-Woodbury formula. This approach enables rapid computation of surface currents accounting for the complex load impedance and supports an arbitrary number of BF associated with the load edge. The purpose of the work. To develop an algorithm for optimizing the complex impedance of a load element with an arbitrary number of BFs on its edge, ensuring matching of the port’s internal resistance with a multi-port structure in the MoM framework. Results. We describe a MoM-based procedure for computing scattering parameters in problems with active/passive ports and different types of lumped loads, and we verify our MoM solver on four microwave models. The deviation from a third-party MoM solver does not exceed 0.82 dB. Feature selective validation method shows that more than 40% of the data points fall into the “Excellent” category. We also propose a load-impedance optimization algorithm that minimizes the reflection coefficient by matching the port internal resistance to the structure’s input impedance. The algorithm’s performance is demonstrated on three microstrip structures, where the average reduction of the reflection level is about 90 dB. Practical significance. The proposed algorithm can be integrated into CAD tools for the design of antennas and microwave devices. The research was carried out at the expense of Russian Science Foundation grant 23-79-10165, https://rscf.ru/project/23-79-10165/.
Problem statement. Modern high-resolution radar systems are an integral part of modern information-measuring and control system for remote sensing of the Earth. Radars, as well as any elements of the measuring system, require calibration, a promising means of which is the use of a transponder (active repeater), since it can replace a full-fledged calibration range. This is due to the fact that the repeater allows you to form a set of virtual objects on the radar image by changing the phase structure of the retransmitted signal. However, due to the imperfection of the transponder control algorithms used, images of virtual objects are defocused. Goal. Select the characteristics of the radar image of the virtual object, which determines the possibility of its use as a reference for calibration of high-resolution radars, and justify the choice made. Results. Computer modeling has shown that radar characteristics such as range and azimuth resolution are not effective in assessing the suitability of virtual objects for high-resolution radar calibration. It is established that instead of them, the cross-sectional area of the image of the formed object or the relative level of the first side maximum should be used. Practical significance. The selected indicators can be used to improve and evaluate the effectiveness of control algorithms and digital signal processing of transponders to expand the permissible range of virtual object removal in which it can be considered acceptable for calibration.
This paper addresses the problem of implementing frequency-selective prototype circuits with fractional-order transfer functions, which are widely used in modern control systems, including robotics and Fractional-Order PID (FOPID) controllers. The main challenge lies in the irrational nature of the fractional-order differentiation operator pα, which precludes its direct physical implementation. To solve this problem, the method of rational interpolation is proposed, enabling the transition from an irrational function to a rational fraction. The study analyzes the asymptotic behavior of the system of interpolation equation s, based on which a necessary con dition for physical realizabil ity is proved: the equality of the degr ees of the numerator and denomi nator of the approximating function (M N=). It is shown that the obtained solution satisfies the realizability conditions for RC circuits. Using a practical example for the case 0.5α =, an approximation of the operator pα is performed. A passive ladder prototype is synthesized, and b ased on it, an active ARC filter is designed using the operational simulation method. Simulation results confi rm the high accuracy of the proposed approach (the implementati on error does not exceed 0.003 dB). A comparative analysis of the rational interpolation method with approximations based on Tayl or series and continued fractions is carried out. It is establishe d that the proposed method provi des lower amplitude and phase r oot mean square errors for approximation orders higher than five.
Problem formulation. Quadcopter control modes, in which the operator is freed from the need to constantly monitor the position of the device, are in demand, and not only by novice pilots, but also by professionals who simultaneously solve payload control problems. In this regard, the issues of developing and configuring sensors for autonomous navigation, which allow stabilizing the position of the quadcopter in space, are currently relevant. Purpose. Development of an algorithm for controlling a quadcopter in the position stabilization mode using an optical image sensor and a laser range meter (lidar) in the absence of an GNSS signal. Results. An algorithm for controlling the quadcopter has been formed, which allows automatically maintaining a given position without affecting the controls and quickly switching from forced movement to stabilizing the position in earth space. It allows you to maintain robustness in conditions of strong noise of the sensor signal, and at the same time achieve the required control quality. Practical significance. An attempt was made to provide a sufficiently accurate positioning of the UAV in a mode similar to the so-called Loiter mode, available only with the presence of GPS Mode signals. Conducting experiments on a real drone allows us to conclude about the fundamental performance of the control algorithm.
In modern fiber-optic sensors based on the interaction of modes in contacting optical fibers, the accuracy of calculating the coupling coefficient between the fibers is critically important. The widely used linearly polarized (LP) mode approximation, which ignores the longitudinal field components, can lead to significant errors. To perform an accurate calculation of hybrid modes of optical fibers, taking into account the core, analyze the structure of surface electromagnetic fields, and determine the coupling coefficient between two contacting parallel fibers, considering all field components, including the longitudinal one. Dependencies of the amplitudes of surface electric field components on the radial mode number for HE and EH hybrid modes in fibers with and without a core are presented. A comparison of the field structures for cases with and without the core has been conducted, revealing qualitative differences in component behavior. It is shown that the longitudinal field component at the cladding boundary is comparable to the transverse components, and its contribution to the mode coupling coefficient reaches a significant value. Field distribution profiles for the HE₁₁ mode in Cartesian coordinates are constructed, allowing the assessment of the amplitude ratio between the longitudinal and transverse components near the cladding boundary. Components of the coupling coefficient for two contacting parallel fibers are calculated, and regions of their maximum interaction are determined. A comparison of the coupling coefficient with and without considering the longitudinal field component is performed; it is demonstrated that neglecting it leads to an error in the coupling coefficient value of up to several tens of percent. Dependencies of the coupling coefficient on the mutual orientation of fiber polarizations, external refractive index, and radial mode number are investigated, revealing patterns of their influence on the efficiency of inter-fiber interaction. The obtained results allow for improving the accuracy of calculations and the design of fiber-optic devices based on inter-fiber interaction through surface fields.
Problem. New method development for protecting extended facility boundaries with widespread machine vision systems, including based on mobile platforms, is urgent. However, security system effectiveness becomes dependent on weather, time, and other factors, previously unaccounted for all-weather intruder detection systems. Objective. Approach justification to constructing a model and effectiveness of border protection, built on the basis of alarm and video surveillance integration, when intrusion risks and possible countermeasures vary in time and space, depending on natural, climatic, physical, geographical and other conditions. Results. Developed spatial-time extended boundary protection model enables daily plan optimization for organizational and technical measures, based on security forces and alarm/machine vision equipment combined using. Practical significance. Developed model permit automated workstation building for security system operator, including intelligent support for management decision.
Problem statement. To increase the reliability of receiving frequency-modulated signals with a compact spectrum and extended phase trajectories in a channel limited by a given frequency mask and in the presence of additive white Gaussian noise (AWGN), algor ithms for receiving a sequence of signals are used. However, these al gorithms require significant computing resources. Computational costs can be reduced by using quasi-coherent algorithms with decision feedback. The aim o Problem statement. To increase the reliability of receiving frequency-modulated signals with a compact spectrum and extended phase trajectories in a channel limited by a given frequency mask and in the presence of additive white Gaussian noise (AWGN), algorithms for receiving a sequence of signals are used. However, these algorithms require significant computing resources. Computational costs can be reduced by using quasi-coherent algorithms with decision feedback. The aim of the work is to increase the noise immunity of receiving frequency—modulated signals with intersymbol phase interference by using quasi-coherent algorithms with double decision feedback at the level of individual symbols. These algorithms provide minimal computational complexity in practical implementation. Results. New algorithms for receiving frequency-modulated signals with extended phase trajectories are presented, which provide a given width of the occupied frequency band and an increased rate of decrease in the level of out-of-band emissions. It is shown that the use of a double decision feedback algorithm provides an energy gain in comparison with a quasi-coherent element-by-element reception without feedback, amounting to about 1.1 dB with an error probability BER = 1·10-4 in the AWGN channel for power-law sinusoidal frequency pulses. When using the algorithm with double decision feedback, when receiving a message of the order of 1 Mbit, the processing time is 2.72 seconds, which is 12 times less than the Viterbi algorithm. The indicated reduction in processing time allows to increase the amount of information transmitted within a given time interval. Practical significance. The proposed quasi-coherent reception algorithms with limited computational complexity can be used in communication systems where strict requirements are placed on computational complexity, spectral compactness and energy efficiency. Such systems include the space segment of broadband access, short-range mobile communication lines, as well as satellite data transmission and digital broadcasting systems. The implementation of algorithms on software-defined radio platforms (SDR) ensures their practical applicability and flexibility of tuning to channel and signal parameters. f the work is to increase the noise immunity of receiv ing frequency—modulated signals with intersymbol phase interference by using quasi-coherent algorithms with double decision feedbac k at the level of individual symbols. These algorithms provide minimal computational complexity in practical implementation. Results. New algorithms for receiving frequency-modulated signa ls with extended phase trajector ies are presented, which provid e a given width of the occupied frequency band and an increased rat e of decrease in the level of out-of-band emissions. It is show n that the use of a double decision feedback algorithm provides an ene rgy gain in comparison with a quasi-coherent element-by-element reception without feedback, amounting to about 1.1 dB with an e rror probability BER = 1·10 −4 in the AWGN channel for power-law sinusoidal frequency pulses. When using the algorithm with double decision feedback, when re ceiving a message of the order of 1 Mbit, the processing time i s 2.72 seconds, which is 12 times less than the Viterbi algorithm. The indicated reduction in processing time allows to increase the amount of information transmitted within a given time interval. Practical significance. The proposed quasi-coherent reception a lgorithms with limited computational complexity can be used in communication systems where strict requirements are placed on comp utational complexity, spectral compactness and energy efficienc y. S u c h s y s t e m s i n c l u d e t h e s p a c e s e g m e n t o f b r o a d b a n d a c c e s s, s h ort-range mobile communication lin es, as well as satellite data transmission and digital broadcasting systems. The implementati on of algorithms on software-defined radio platforms (SDR) ensu res their practical applicability and flexibility of tuning to channel and signal parameters.
This paper addresses the task of calibrating a radar antenna reflector using spacecraft. For mobile and relocatable radars, a critical objective is the rapid measurement and elimination of systematic angular coordinate measurement errors induced by radar antenna reflector misalignment. The work aims to assess the feasibility of rapid calibration for an L-band Active Electronically Scanned Array (AESA) radar antenna reflector using spacecraft. The principal contemporary methods employed for spacecraft-based radar antenna reflector calibration are examined. The paper defines radar antenna reflector calibration as estimating the position of the radar antenna's electrical boresight axis in three angular dimensions. A mathematical framework for determining these three boresight axis orientation angles is proposed. The article provides a detailed description of two proposed methods for calibrating the antenna reflector of an L-band AESA radar: Active Radar Data Collection: Utilizing active radar tracking of Low-Earth-Orbit (LEO) spacecraft, employing orbital data from the NORAD catalog. Passive Radar Data Collection: Utilizing passive radar methods tracking signals emitted by navigation systems (e.g., GLONASS), employing ephemeris data obtained from the navigation satellites. The paper presents mathematical modeling of the proposed radar antenna reflector calibration methods. This modeling includes estimates of measurement noise-induced errors, data collection time requirements and the resulting radar antenna reflector calibration error. An analysis is conducted of experimental results from an L-band AESA radar: calibration of radar antenna reflector based on two data collection sessions using LEO spacecraft and using GLONASS navigation signals. Using the computed radar antenna reflector calibration, the systematic error in measuring angular coordinates (azimuth and elevation) is calculated by tracking a dedicated spacecraft equipped with corner reflectors (ensuring its position determination accuracy is guaranteed to be ≤ 10 meters). A conclusion is drawn regarding the capability of the proposed calibration methods to achieve rapid calibration (on the order of couple minutes) of the radar antenna reflector using either LEO spacecraft or navigation systems, while achieving a final systematic angular coordinate measurement error on the order of couple arc-minutes.
Formulation of the problem. Sign al spectrum analysis is a deman ded task in the development of various radio engineering and te lecommunication devices. Commonly used spectrum analyzer devices have a high cost and a limited frequency band in real–time sign al processing (on the order of tens of megahertz), which increases the likelihood of missing signals. Currently, the options for analyzing signals in a wide frequency band are the use of multichannel su b—sampling using digital signal sample processing methods. The paper demonstrates the restoration of the amplitude spectrum of s ignals in a wide frequency band during parallel operation of se veral asynchronous sampling channels with their spectral analysis, th e deployment of frequency responses of channels from the first Nyquist zone to high zones, and subsequent joint processing of the expanded spectra to obtain the spectrum of the input signal. This spectrum is called the reconstructed spectrum of the input sign al. For this purpose, it is assumed that several processing cha nnels with parallel analog-to-digital converters will be used, which differ in the value of the subsampling frequency. An amplitude spectrum is constructed in each channel. At the final stage, the digital processor processes the received amplitude spectra together to construct the final amplitude spectrum of the input signal. Goal. Development of a block for digitizing and restoring the a mplitude spectrum of a broadband signal using multichannel subs ampling methods and construction of an experimental stand for testing the block. Res ult s. A prot otype ofablock for di gi ti zing and res tori ng t he amplitude spectrum of a broadba nd signal using the multichann el asynchronous subsampling method and an experimental setup for t esting the characteristics of the block model were developed. The results were compared with the operation of the BARS-MSA-26S sp ectrum analyzer [1] for single- and multi-signal modes accordin g to the criterion of signal position compliance in the operating frequency range from 0 to 18 GHz with a frequency resolution of 1 MHz. The results demonstrate the corr ect restoration of the spectrum of the original signal. A special feature is the absence of si de responses and the independence of the noise level from the freque ncy in the entire operating range up to 18 GHz. It should be no ted that in comparison with the BARS-MSA-26S spectrum analyzer, the developed block for digitizing and restoring the amplitude spe ctrum of signals using multichannel subsampling methods is cheap er, can provide signal processing in real time in a band of up to 1200 MHz and a limited width of the Nyquist zone of the ADC used (the real-time viewing band for the BARS-MSA-26S spectrum ana lyzer is 20 MHz). Practical significance. A block for digitizing and restoring th e amplitude spectrum of a signal in a wide frequency band using the multichannel subsampling method and an experimental stand for test ing the operation of the block have been developed and can be used in the development of modern radio engineering systems, since the block is distinguished by the ability to operate in real time in a wide instantaneous operating frequency band with high frequency resolution.
