Introduction. Radio communication systems for small Earth-orbiting objects possess a number of specific features associated with their application area, thus being expected to meet conflicting requirements. These include, on the one hand, provision of a high data transfer rate (up to 20 Mbps) and, on the other, operation at large distances of up to 150 km or more, while having small dimensions and power consumption (usually no more than 5…20 W). The main share of energy required by onboard radio communication systems of small Earth-orbiting objects is consumed by the power amplifier. Therefore, such communication systems should use modulation with the lowest possible crest factor.

Aim. To investigate the effect of the parameters and operating modes of the amplifier on those of the radio communication system, such as its output power, efficiency, out-of-band transmitter radiation, and receiver sensitivity for signals with different types of modulation and different crest factor values.

Materials and methods. The laboratory bench consisted of pseudo-random sequence and carrier generators; QPSK, OQPSK, and SR-FQPSK transmitters; amplifier; QPSK, OQPSK, and SR-FQPSK receivers; attenuators; spectrum analyzer; power meter; and error meter. The parameters were measured using the methods embedded in the devices: spectrum analyzer, power meter, and error meter.

Results. The conducted experiments showed that operation of the amplifier in a nonlinear mode leads to an increase in the efficiency and output power in the field of compression. The out-of-band power is maximum for a QPSK modulated signal. The closer to the compression region the amplifier works and the larger the crest factor of the signal, the lower the sensitivity of the receiver.

Conclusion. The use of a low crest factor modulation (SR-FQPSK in the case of this study) ensures the maximum output power of the amplifier, the maximum efficiency, and the minimum level of out-of-band radiation. This increases the energy efficiency of radio communication systems and extends the communication range, thus allowing a more efficient use of frequency separation channel

Introduction. The current trend in the production of miniaturized electronic devices with improved computing power and performance leads to an increase in the density of interconnections on printed circuit boards (PCBs) and a reduction in the dimensions of such conductive pattern elements, as tracks and gaps, contact pads of components and vias. At the same time, the growing interconnection density decreases the reliability of devices and increases the number of defects in production. In this connection, the development of approaches to quantitative evaluation of the manufacturability of PCB blanks that meet the acceptance criteria represents a relevant research task. A significant share of defects is introduced at the photolithography stage; therefore, an a priori estimation of the number of defects before fabrication and determination of approaches to their reduction are of particular significance.

Aim. Development and experimental verification of an analytical model for determining the yield probability of PCB blanks of acceptable quality for the photolithography stage.

Materials and methods. An analysis of reasons for emergence of defects in the process of photolithography was conducted. On this basis, the manufacturing parameters that describe the defect value, i.e., conductive pattern distortion and conductor edge roughness, were established. A mathematical model describing the probability of defect-free manufacturing of PCB blanks was proposed. Conductor width and conductor gap size were used as estimated design parameters of PCBs. The quality criteria for the design and acceptance of PCBs were determined based on international standards.

Results. A methodology for experimental verification of the proposed probabilistic model by means of processing and statistical analysis of photomask and blank images was developed. Difficulties associated with the creation of datasets and their processing were considered. The adequacy of the model for a laboratory production line was confirmed. For the investigated process, the dependencies of manufacturing parameters on the designed conductor width were determined and the corresponding adjustments of the process were introduced. This allowed the probability of obtaining PCB blanks of acceptable quality to be increased.

Conclusion. The results of probability calculations obtained using the proposed model can be used as an indicator of required changes in the design of a printed assembly or for assessing the risks and reserves required by the manufacturer for the production of high-complexity specimens.

Introduction. Intelligent driver assistance systems are increasingly employing radar systems to detect, resolve, and track various classes of targets. The use of MIMO-based distributed systems allow the characteristics of object resolution by angle to be significantly improved. However, this is associated with the difficulty to ensure a coherent mode of processing data entering from two or more radar systems. This work compares a millimeter wavelength range radar system with improved angular resolution with a monostatic system. The issue of ensuring synchronization of radars comprising the system under study is addressed.

Aim. To increase the angular resolution of a distributed radar system with tandem coherent signal processing of two MIMO radars.

Materials and methods. The resolution of a system consisting of two spaced radars was investigated experimentally using a fully functional layout. Algorithms for phase synchronization and collaborative digital signal processing, along with appropriate software, were developed.

Results. The use of a common external reference signal source in MIMO radars makes it possible to implement a coherent system operation mode. Placement of two spaced MIMO radars ensures the formation of a bistatic virtual antenna array, which doubles the angle resolution, compared with a radar whose number of receiving channels is two times smaller than the size of a bistatic virtual array.

Conclusion. The conducted experimental studies demonstrated an increase in angular coordinate resolution during the formation of a bistatic virtual antenna array. The use of an external reference generator ensures the coherent operation of two radars, improving the accuracy of mutual phase synchronization in the channels of bistatic subarrays by several degrees.

Introduction. Determination of the angular coordinates of the electromagnetic wave received from a radio source and estimating its parameters constitute the main tasks of radio monitoring. For direction finding of radio sources, classical amplitude, phase, and correlation methods are currently used. Amplitude methods involve the directional properties of the antenna. Phase and correlation methods are based on the difference in delays of signals received by spaced antenna elements. The information parameter in these methods consists in the phase front of the incident wave, which is orthogonal to the direction of its propagation. In this article, we consider a method for estimating the spatial parameters of a signal based on the orthogonality of the polarization plane relative to the propagation of a radio wave.

Aim. Simulation of an algorithm for estimating the polarization and spatial parameters of a radio source signal based on the fixation of three projections of the electromagnetic field using a triorthogonal antenna system.

Materials and methods. Mathematical simulation of an algorithm for spatial polarization processing of signals received by a triorthogonal antenna element in the MATLAB software environment.

Results. The developed mathematical model of an algorithm for processing a spatially polarized signal received by a triorthogonal antenna system was used to obtain dependencies for assessing the polarization and spatial parameters of the received electromagnetic wave on the signal-to-noise ratio in the 50 kHz band. The obtained characteristics were used to determine the maximum standard deviations of the azimuth, elevation angle, ellipticity coefficient, and ellipse inclination. A comparison of the average level of energy loss of the received signal calculated by the spatial polarization algorithm and when receiving only the vertical component of the field, depending on the ellipticity coefficient and elevation angle, was carried out. As a result, spatial polarization processing allows a greater energy of the incoming signal to be employed, with the greatest gain being observed at elevation angles greater than 40°.

Conclusion. The spatial polarization processing algorithm of three electromagnetic field projections makes it possible to estimate the spatial and polarization parameters of a propagating electromagnetic wave. Evaluation is possible provided that both field components – horizontal and vertical – are present in the signal. When determining the spatial and polarization parameters of the wave, the signal can be depolarized, thereby increasing its energy.

Introduction. Temporal synchronization is a relevant issue for various radio communication, radio navigation, and radar systems, for determination of time points for impulse signal arrival and positioning. The radio communication problem should ensure an error-free signal transmission via a radio channel at a maximum possible transmission rate. The known solutions of the temporal synchronization problem in the case of orthogonal frequency-division multiplexing (OFDM) signal transmission employ a guard interval for computing the periodic autocorrelation function of the analyzed OFDM-signal, which leads to unproductive costs of the time-frequency resource. In this paper, we discuss the problem of processing and analysis of OFDM-signals in the presence of noise and estimation of the time point of OFDM-signal arrival.

Aim. Development of an algorithm for time synchronization of OFDM signals in the presence of noise in the radio communication channel using fast computing algorithms based on the harmonic wavelet transform.

Materials and methods. The research was conducted using the methods of wavelet transform and wavelet-based signal processing including the harmonic wavelet transform on the basis of the octave filter bank, fast computational algorithms aimed at computing the harmonic wavelet transform.

Results. A new method for OFDM signal processing in the presence of noise based on the octave harmonic wavelet transform is suggested. This method allows determination of boundaries of orthogonality intervals in an OFDM-signal along with the moments of the onset and end of orthogonality intervals. An algorithm for finding the time point of OFDM signal arrival is proposed. It is shown that the increase of the analysis window of an OFDM signal leads to an improvement in the temporal synchronization accuracy, although requiring more time for establishing synchronization. The suggested approach does not employ the guard interval, thus increasing the information transmission rate.

Conclusion. The harmonic wavelet transform is effective for the analysis and processing of OFDM signals. Furthermore, the aforementioned transform works perfectly well both in the absence and in the presence of noise. The harmonic wavelet transform allows determination of boundaries of orthogonality intervals with maximum possible accuracy. Based on complex vectors, which correspond to the boundaries of orthogonality intervals, the time point of OFDM-signal arrival can be found.

Introduction. A detection algorithm that ensures a constant value of the false alarm rate against the background of nonstationary noise, whose average value varies within a sliding window. The proposed algorithm is based on a linear approximation of the average noise level within a sliding window using the least squares method with subsequent compensation for changes in the average value. The effectiveness of the proposed algorithm was assessed using a simulation method. When working against the background of nonstationary noise, the proposed algorithm reduces the detection threshold compared to an algorithm based on calculating noise dispersion in a sliding window.

Aim. Development of a detection algorithm that takes into account the mathematical expectation of noise within a sliding window when calculating the detection threshold.

Materials and methods. The research was carried out using the mathematical apparatus of probability theory and estimation theory. The effectiveness of the developed algorithm was assessed by mathematical simulation.

Results. A detection algorithm that ensures a constant value of the false alarm value F when detecting a signal against the background of noise was developed. When working against the background of nonstationary noise, the algorithm provides the threshold signal-to-noise ratio of 3.57 dB lower than that provided by an algorithm based on calculating noise dispersion by averaging the elements of a sliding window.

Conclusion. This paper proposes an algorithm for stabilizing the false alarm rate based on assessing the noise trend and its subsequent compensation in the subtracting device. The algorithm ensures the constant value of the false alarm rate under changes in the average value of noise within a sliding window.

Introduction. When shaping radar signals, the transmission paths of pulsed radars with active electronically scanned arrays (AESA) frequently use a periodic charge/discharge of capacitive energy storage devices. In such cases, the power amplifier of the transmitting module consumes electricity over short time intervals. However, the pulsed nature of the amplifier operation causes uneven power consumption of the storage charger. This leads to a deterioration in the electromagnetic compatibility of radar equipment and a decrease in operation reliability due to the additional load on the power supply system. To reduce the unevenness of power consumption, smoothing choke сoils are used together with storage devices, which degrade the weight–size characteristics and the entire performance of the radar. Thus, the task of reducing the uneven power consumption droop of transmitting modules without compromising their weight–size characteristics appears relevant.

Aim. To demonstrate the possibility of constructing a charger for a capacitive storage device that ensures uniform power consumption of the transmitting module due to constant charge power, with the purpose of improving a number of technical characteristics of the AESA.

Materials and methods. A review of methods for charging capacitive storage devices and an analysis of the possibility of constructing a charger for a storage device with constant power using the theory of electrical circuits. The operation of a constant-power charger was analyzed in the Micro-Cap environment and using its experimental prototype, taking the actual durations and frequencies of radar signals into account.

Results. A new charger for a capacitive storage device with constant power is proposed and the principle of its operation is considered. A simulation model and an experimental prototype are developed, which confirmed the possibility of significantly reducing the power consumption droop of the AESA transmitting module without the use of bulky smoothing chokes. Directions for further improvement of the charger are outlined.

Conclusion. The proposed 120-W capacitor storage charger for the radar AESA transmitting module is characterized by simplicity of implementation and a high energy efficiency of the charge. This charger can be recommended for use in advanced radars with AESA for the purpose of improving a number of technical characteristics.

Introduction. The entire concept of product development is currently undergoing significant changes. The application of digital twin technology allows the focus of development to be shifted to the earliest stages, thereby significantly reducing not only potential risks, but also saving the required time and material resources. Classical statistical approaches to evaluating the detection capabilities of radar systems fail to provide a complete dynamic picture due to the large number of varying parameters.

Aim. Development of an algorithmic support for simulating the radar detection process using digital twins of the antenna system and the observation object.

Materials and methods. Radar equation multipliers were presented by frequency, angular, polarization dependencies, calculated using their digital models (twins). Numerical electrodynamics methods were used to calculate the directivity characteristics of the antenna element and the backscattering characteristics of the object, implemented in the ANSYS HFSS automated design environment. Mathematical and computer modeling methods were used to coordinate the results of numerical simulations. The MATLAB application package was used to form the directivity characteristics of the antenna array, to obtain the dynamic signal-to-noise ratio, and to analyze the probability of detection.

Results. The possibility of using digital twin technology to verify the detection capability for a radar system when observing an object of the specified class is demonstrated. The signal-to-noise dynamic dependence of the given radar system, space object, and observation scenario, presented by their digital models, was calculated. The function of detection probability density was calculated, which demonstrated an insufficient detection capacity of a radar system in the case of observation of such type of objects.

Conclusion. The significance of the present study lies in the development of an algorithmic support using digital twin technology. The developed support can be used to estimate the probability of detection of specified objects by a radar system when implementing various technical solutions at early stages of its development.

Introduction. Orthogonal frequency division multiplexing (OFDM) has become a popular wideband digital communication scheme. Research studies into the use of new telecommunication signals, including those synthesized based on the 5G standard, in bistatic radar indicate the possibility of providing high resolution in terms of range and speed. In comparison with, e.g., a digital video broadcasting signal on the ground (DVB-T), 5G transmission depends on the user demand. In the absence of active users, the 5G downlink signal includes only the synchronization signal block (SSB), which is constantly present. Research into the possibility of using the 5G synchronization block in bistatic radar represents a relevant task, enabling radar monitoring in areas where the use of 5G has not yet been sufficiently developed among the population.

Aim. Analysis of 5G synchronization signal, simulation of signal processing in bistatic radar, and conducting analysis of experimental results.

Materials and methods. The research was conducted using the theory of signal processing in bistatic radar, the standard and structure of the 5G synchronization block signal, and comparative analysis. The cross-ambiguity function of bistatic radar was calculated by computer simulation in MATLAB and by experimental studies. A passenger car (Hyundai ix35) was used as the object of observation. Signals were received and recorded using the Ettus USRP B210 SDR platform.

Results. Simulation and experimental studies were conducted in the 5G signal coverage area. The results obtained show that a bistatic radar system based on the 5G synchronization signal block is capable of detecting moving targets.

Conclusion. The 5G synchronization signal block produces satisfactory results when determining the range. At the same time, the speed cannot be measured precisely. In order to eliminate the ambiguity when measuring the speed, we propose to use a two-stage signal synthesized based on OFDM, with different repetition periods of synchronization signals and subsequent multiplicative processing. A bistatic radar system based on SSB 5G can become one of the subsystems for monitoring vehicles.

Introduction. In oncology, accurate classification of lung cancer mutations plays a key role in developing personalized treatment strategies. Lung cancer, distinguished by its heterogeneity, presents significant challenges in diagnosis and treatment, requiring innovative approaches for precise mutation classification.

Aim. To introduce a new methodology combining deep learning and radiomic features extracted from computed tomography (CT) images for classification of lung cancer mutations.

Materials and methods. The ResNet18 architecture was adapted to integrate radiomic features directly into the deep learning workflow. The use of a convolutional neural network enabled large volumes of data to be processed, surpassing the performance of conventional methods. The analysis involved identification of significant radiomic features, such as texture, shape, and tumor boundaries, which were automatically extracted and used to train the model. The technique was tested on an extensive dataset containing CT images of various lung cancer subtypes, including adenocarcinoma and squamous cell carcinoma.

Results. The model demonstrated an overall mutation classification accuracy of 98.6 %, significantly exceeding the results achieved using conventional approaches. The high accuracy confirms the effectiveness of combining radiomic features with deep learning in identifying various genetic mutations in lung cancer. The results also indicate the high potential of the method in the development of non-invasive diagnostic tools and improving personalized treatment approaches.

Conclusion. This work emphasizes the importance of integrating high-level abstractions of deep learning models with detailed analysis of radiomic data to enhance the predictive accuracy of non-invasive diagnostic tools, which could significantly improve diagnostic processes and contribute to the development of treatment strategies in oncology.