Вісник НТУУ «КПІ». Радіотехніка, радіоапаратобудування : збірник наукових праць, Вип. 97
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Документ Відкритий доступ Method for Detecting Small Aerial Objects Appearing in Field of View in Controlled Part of Celestial Sphere in Infrared Range(КПІ ім. Ігоря Сікорського, 2024) Agaev, F. G.; Asadov, H. H.; Aliyeva, G. V.The article is devoted to the developed method of infrared detection of group remote high-temperature objects. The problem of searching for the extremum of the total infrared radiation of a group of non-identical thermal objects carrying out a group flight is formulated and solved using the variational optimization method. Examples of such objects include the flight of aircraft in a group, ground scenes involving a group of objects of interest, temperature diagnostics of various points of buildings, control of automobile traffic on highways, control of group flights of birds, drones, etc. A condition has been determined under which the total value of the infrared radiation flux of thermal elements in the group reaches an extreme value. The regression relationship function between the emission coefficient of the thermal elements of the group and the atmospheric transmission coefficient has been calculated. The problem of optimal control of small thermal objects randomly distributed in the atmosphere is practically solved using a ground-based multiradar system in which elements of a multi-radar system monitor flying objects with different values of the radiation coefficient on the routes and different atmospheric transparencies. The proposed method can be used for remote control of flight or the functioning of a group of flying thermal objects with different values of the radiation coefficient with a special procedure for selecting a controlled aircraft for observation by an element of a multi-radar system. The property of the extremum of the total IR radiation flux was found in the inverse relationship between the radiation coefficients of all controlled flying objects and the transparency of the atmosphere along the route between the multi-radar element and the controlled flying object.Документ Відкритий доступ Advanced Edge Detection Techniques for Enhanced Diabetic Retinopathy Diagnosis Using Machine Learning(КПІ ім. Ігоря Сікорського, 2024) Basarab, M. R.; Ivanko, K. O.Diabetic retinopathy (DR) represents one of the most serious complications associated with diabetes mellitus, posing a significant threat to vision and leading to severe impairment and potential blindness if not diagnosed and treated promptly. The study investigates the integration of advanced edge detection techniques with machine learning algorithms to enhance the precision and effectiveness of DR diagnosis. By leveraging the APTOS 2019 Blindness Detection dataset, the research employs a combination of edge detection methods such as the Sobel operator and the Canny edge detector, alongside advanced preprocessing techniques and sophisticated feature extraction methods. The study reveals that the synergy between these edge detection techniques and machine learning significantly boosts the diagnostic accuracy of neural networks. Specifically, the accuracy for multiclass classification (spanning five categories: No diabetic retinopathy, Mild, Moderate, Severe, and Proliferative diabetic retinopathy) improved from 78.5% to an impressive 88.2%. This marked enhancement underscores the potential of these techniques in refining the diagnostic processes for early DR detection. By improving the accuracy of classification, this approach not only facilitates early intervention but also plays a crucial role in reducing the risk of severe vision loss among patients with diabetes. The findings of this study emphasize the importance of integrating advanced image processing techniques with machine learning frameworks in medical diagnostics. The improved outcomes demonstrated in this research highlight the potential for such technological advancements to contribute meaningfully to the field of ophthalmology, leading to better patient care and potentially transforming the standard of practice in DR diagnosis.Документ Відкритий доступ Scattering of Electromagnetic Waves by Loss and Gain Systems of Dielectric Resonators(КПІ ім. Ігоря Сікорського, 2024) Trubin, A. A.The problem of wave scattering on a system of coupled Dielectric Resonators (DR) made of an active or absorbing dielectric is considered. The solution of the scattering problem is decomposed over the field of natural oscillations of the DR system. The field describing the natural oscillations of the DR system is decomposed by the field of partial resonators, which are made of a dielectric with a complex permittivity. A system of equations is given, the solution of which allows to determine the frequencies and amplitudes of the natural oscillations of the system of active or absorbing resonators. In the work, a new system of linear equations for amplitudes of forced oscillations of resonators was obtained. General solutions for the scattering field on resonators located in a regular transmission line or in a break of a regular line have been found. Several examples of calculation of the frequency dependences of the scattering matrix for different bands to pand band-pass filters, consisting of coupled active or absorbing dielectric resonators are given. The possibilities of the proposed method are demonstrated on the example of optimization of scattering characteristics on band-stop and band-pass filters made of an active dielectric. It is shown that the use of resonators made of an active dielectric will make it possible to build and optimize the frequency characteristics of a new class of devices that simultaneously perform the functions of filters and amplifiers. The conditions under which it is possible to build filters with the functions of amplifiers are defined. In the future, the proposed devices may find application in optical communication systems.Документ Відкритий доступ Neural Networks Detection of Low-Amplitude Components on ECG Using Modified Wavelet Transform(КПІ ім. Ігоря Сікорського, 2024) Mnevets, A. V.; Ivanushkina, N. G.This study is devoted to identification of low amplitude components from ECG signals by different timefrequency analysis methods when main power spectrum falls on high-amplitude components. It was also analyzed the problem of choosing correct scale system for determination low-amplitude components on the scalogram by artificial intelligence models. As a result of the study, several modifications of the continuous wavelet transform were proposed. First modification was based on the use of a scaling function and a modified wavelet. Second modification was based on the use of cosine similarity at each iteration of convolution followed by the use of a scaling function. The main idea of the study was to modify the wavelet transform in such a way as to select the components which has the target amplitude and reduce all other components that complicate the neural networks analysis of the interested fragments of the signal. Also, possible procedures for signal restoring were proposed for preserving the effect of using scaling modifications. The testing of the proposed modified algorithms was carried out on the basis of artificially created signals as well as on the basis of real ECG signals with late potentials superimposed on them. Visual analysis of scalograms and signal reconstructions obtained using the modified wavelet transform showed that the modified wavelet transform is capable of extracting low-amplitude components from the signal with much greater spectral power than the transform without modifications. In addition, the ability of common neural network models to distinguish between cardiac cycles with and without late potentials was tested. As a result, it was found that models that were trained on scalograms obtained using a modified wavelet transform train faster and are less susceptible to local minima stucking. The results of classification of signals with and without late potentials based on trained neural network models showed that training using scalograms obtained on the base of a modified wavelet transform allows achieving 99% classification accuracy, which is 1-49% more than that using scalograms obtained on the base of on the classical wavelet transform.Документ Відкритий доступ Mathematical Modeling the Electrical Impedance of Piezoceramic Disk Oscillating in Wide Frequency Range (Part 2. Medium Frequencies)(КПІ ім. Ігоря Сікорського, 2024) Bazilo, C. V.; Faure, E. V.; Usyk, L. M.; Tuz, V. V.; Chorniy, A. M.This paper presents further developments in mathematical modeling of the electrical impedance of a piezoceramic disk in a wide frequency range, specifically focusing on the mid-frequency range, i.e., when the elastic wavelength becomes commensurate with the radius of the piezoceramic disk, which is important for numerous modern applications. A mathematical model was developed for disk piezoelectric transducers made of piezoceramics to estimate their electrical impedance and quasi-static electrical capacity in the medium frequency range basing on their geometrical, physical, and mechanical characteristics. The research has found that a piezoceramic disc attains electromechanical anti-resonance in the medium frequency range at frequency, at which its electrical impedance follows to infinity. This effect is due to the polarization charges being completely compensated by the electric charge, when the electric current vanishes and energy consumption from the generator is absent. The calculations proved that at frequencies close to the first thickness resonance (corresponding to the dimensionless wave number from 40 to 60), the radial displacements of material particles of the disk vanish. A very rapid decrease in the levels of radial shifts with a simultaneous increase in the electromechanical resonance number was noted. The evaluation of the mechanical quality factor of piezoceramic disk elements, obtained with the developed mathematical model, closely correlates with real values, which is confirmed by the high agreement between theoretical and experimental results.Документ Відкритий доступ Експериментальне дослiдження впливу рупора на чутливiсть ультразвукового далекомiра(КПІ ім. Ігоря Сікорського, 2024) Лемеха, В. О.; Шульга, А. В.Розглянуто завдання, де виникає необхiднiсть вимiрювання точної вiдстанi мiж об’єктами. Встановлено, що ефективними для вимiрювання вiдстанi є ультразвуковi далекомiри завдяки їхнiй безконтактнiй роботi, високiй точностi, широкому дiапазону вимiрювань та здатностi функцiонувати в рiзних умовах. Використання рупора в ультразвукових далекомiрах є досить поширеною практикою, оскiльки вони дозволяють пiдвищити їх чутливiсть. Вiдомо, що iснує багато рiзних типiв рупорiв, якi вiдрiзняються формою, розмiрами та матерiалами. Однак, найпоширенiшими з них є конiчнi рупори, якi не вимагають складностi при виготовленнi та мають досить низьку вартiсть. Зпроєктовано та виготовлено за допомогою ЗD-друку шiсть варiантiв дослiдних рупорiв з довжиною вiд 10 мм до 60 мм. Розроблено експериментальний стенд з поворотною платформою, який має приймача та передавача, мiж якими вимiрюється вiдстань та дiаграми спрямованостi звукового тиску. Експериментальнi дослiдження проводились на вiдстанях вiд одного до трьох метрiв з iнтервалом 0.5 метра. Оброблено всi результати вимiрювання та побудованi дiаграми спрямованостi для всiх випадкiв, використовуючи один з виготовлених рупорiв. Представлено дiаграми спрямованостi саме для мiнiмальної i максимальної вiдстаней обраного дiапазону. Дослiдження показало, що застосування рупора довжиною 50 або 60 мм призвело до пiдвищення рiвня звукового тиску на 10 дБ вiдносно вимiрювань без рупора. Але при зменшеннi довжини рупора менше 40 мм спостерiгається зниження ефективностi випромiнювання звуку. Це пояснюється порушенням оптимальних умов для формування звукової хвилi, що призводить до втрат енергiї та розширення дiаграми спрямованостi. Обґрунтовано вибiр довжини рупора, при якiй не вiдбуваються падiння ефективностi випромiнювання звукових хвиль.Документ Відкритий доступ One-Bit Spectrum Sensing Peculiarities(КПІ ім. Ігоря Сікорського, 2024) Buhaiov, M. V.The use of autonomous sensors for analyzing wide bands of radio frequency spectrum requires using the highspeed analog-to-digital converters (ADC). The operation of such devices with high bit resolution requires several watts of power. One-bit ADC will reduce power consumption and simplify the analog part of the receiver. The goal of the research is to determine the features and conditions under which it is advisable to analyze the radio frequency spectrum in a sophisticated radio electronic environment using a one-bit ADC. The problem of using such ADC is the deterioration of the signal-to-noise ratio (SNR) and the occurrence of spurious spectral components at its’ medium and high values. The task of spectrum sensing is complicated by the fact that a large number of signals with different values of bandwidth and SNR can be simultaneously present in the analyzed frequency band. After a one-bit ADC, the energy of the complex signal remains unchanged regardless of its shape. Therefore, at high SNR values, the signal energy flows into spurious spectral components. When the bandwidth of the signal increases to 30% of analyzed frequency range and higher, the spurious spectral components are transformed into a broadband pedestal. Analytical dependencies have been obtained that allow us to calculate the values of the SNR at which signals can be detected and spurious spectral components appear. These dependencies take into account the parameters of the Welch periodogram and the level of spectrum occupancy. The results of the analysis of real signals showed that the shape of the signal spectrum after one-bit ADC repeats the shape of the spectrum after an 8-bit ADC, except for the absence of some weak signals. The cost for simplified hardware implementation and lower power consumption when using one-bit ADC compared to ADC with higher resolution is a narrowing of the dynamic range of signals. The use of one-bit ADC for spectrum sensing will be justified only when there is information on the analyzed bandwidth occupancy and the SNR of the signals that can be observed.Документ Відкритий доступ Математична модель алгоритма та експериментальне дослiдження точностi вимiрювання девiацiї частоти ЛЧМ сигналу з низькою спектральною щiльнiстю потужностi(КПІ ім. Ігоря Сікорського, 2024) Стейскал, А. Б.; Войтко, В. В.; Марченко, А. О.У статтi запропоновано розв’язувальне правило алгоритму вимiрювання девiацiї частоти лiнiйночастотно-модульованого сигналу з низькою спектральною щiльнiстю потужностi для дискретної моделi автокореляцiйного приймача з квадратурною обробкою та розглянуто варiант зниження тривалостi етапу визначення девiацiї частоти сеансу радiомонiторингу. Синтезовано функцiональний вузол вимiрювання девiацiї частоти лiнiйно-частотно-модульованого сигналу з низькою спектральною щiльнiстю потужностi. Розроблено алгоритм процедури визначення девiацiї частоти лiнiйно-частотномодульованого сигналу.Документ Відкритий доступ Mathematical Model of Shifted Time of Combined Signal as Part of Fragments with Linear and Quadratic Frequency Modulation(КПІ ім. Ігоря Сікорського, 2024) Kostyria, O. O.; Hryzo, A. A.; Solomonenko, Yu. S.; Dodukh, O. M.; Biernik, Ye. V.The issues of synthesis of nonlinear-frequency modulated probing signals, which, in comparison with wellknown linear-frequency modulated signals, have a lower maximum level of side lobes of the autocorrelation function, have a practical orientation, relate to actual problems of theory and practice of forming signals with intra-pulse modulation for radio electronic means for various purposes. The paper considers a combined nonlinear-frequency modulated signal consisting of linearly and quadratically-frequency modulated fragments. The peculiarity of the proposed approach to the description of its mathematical model is the introduction of frequency-phase compensation components, which reduces the maximum level of the side lobes of the autocorrelation function of the signal. Calculation of values of compensation components is based on consideration of the effect of derivatives of function of instantaneous phase of fragments up to the most significant order inclusive. The limitation of the method should include the requirement for the existence of their final quantity. In the first section of the article, an analysis of known studies and publications is carried out, which states that for the mathematical model of shifted time, considered in the work, the proposed method of compensating for frequency-phase distortions has not been previously considered. Therefore, in the second section of the work, the corresponding task of the study is formulated. In order to achieve the formulated task of research, the third section of the work develops a mathematical model of the shifted time of the combined signal, which contains the compensatory components of the specified distortions. The importance of their consideration in the resulting signal is theoretically substantiated and clearly demonstrated. As a result of the research, the theory of synthesis of combined signals has been developed, the composition and determination of the magnitude of frequency-phase distortions, which are caused by the appearance of the third derivative of the instantaneous phase function of the quadraticallyfrequency modulated fragment, have been established. As a direction for further research, it is planned to develop and study a mathematical model of shifted time of a three-fragment combined signal with a quadratically-frequency modulated fragment.