Visnyk NTUU KPI Seriia - Radiotekhnika Radioaparatobuduvannia

Extending the Method for Development of Double-Loop Continuous Tracking Systems to Discrete Equivalents

V. B. Revenko — 2025-03-30

Solutions to increase the accuracy of radio systems are analyzed. It is shown that invariance in a single-loop automatic control system affects its stability.

Article [13] offers to apply a method for the synthesis of continuous high precision double-loop automatic control systems which are equivalent to combined systems in conditions when some values (entry useful action) can't be measured for development of tracking systems (in particular, radio systems, where the entry useful action can't be measured, and therefore combined control is impossible).

The article considers extension of the method for the synthesis of double-loop automatic control systems to discrete systems equivalent to combined systems in an environment with simultaneous entry useful (preset) action and external disturbances and interferences.

The developed method makes it possible to synthesize discrete high-precision automatic control tracking systems equivalent to combined ones in an environment with a controlled variable (entry useful action) which cannot be measured. A discrete transfer function from an error in double-loop system (5), an invariance condition (6), and a characteristic equation (8) are obtained. In this case, the numerator polynomial of the transfer function from error must have a difference of polynomials.

The article demonstrates that invariance conditions (improved accuracy) can be achieved without any destabilization in the first loop. In this discrete tracking system equivalence to combined systems is achieved by two control loops and not by three loops as in the differential coupling method.

A double-loop discrete automatic control system equivalent to a combined system was synthesized. A stochastic regulator was calculated and made, and the influence of this regulator on the astatism of the system (that is, on its accuracy) was analyzed.

The proposed method can be used to develop discrete tracking systems (especially radio systems, where entry useful action cannot be measured due to interference), and it can be applied for laser radar tracking systems, and control systems for aircraft of various purposes.

Amplitude Direction Finder of Radio Frequency Emitters for Unmanned Aerial Vehicle

M. V. Buhaiov — 2025-03-30

The detection and localization of low-power radio frequency emitters (RFE) in populated areas using stationary spectrum sensing (SS) equipment is ineffective due to the lack of line of sight in shadowing effect. To solve this problem, it is advisable to place the SS equipment on a small unmanned aerial vehicle (UAV). The limitations of this solution are low time for data collection and processing and the low computing power of SS device. This leads to a decrease in search capabilities of SS both in terms of spatial coordinates and frequency, which is critical in conditions of high density of RFE. The aim of this article is to increase the speed of RFE searching using a UAV-mounted SS device under time, weight, and energy constraints by using a system of broadband directional antennas and multichannel sequential signal processing. The amplitude direction finding method was chosen to estimate the direction of radio wave arrival, taking into account the mass and computational limitations of the SS device placed on the UAV. The proposed structure of the antenna system contains six log-periodic antennas spaced in a circle by 60°. To process the received signal, a multichannel sequential analysis scheme is proposed, in which one scanning receiver is alternately connected to each of the antennas. It is shown that for this scheme, the parameter to be optimized is the flight speed of the UAV. A generalized expression for calculating this value is obtained. An expression for approximating the main lobe of the antenna radiation pattern in form of a Gaussian function is obtained. A procedure for calculating the direction on RFE by comparing the amplitudes of the received signals by two neighboring antennas is developed. Recommendations to avoid ambiguities in calculation angle of arrival for the case of several RFE are given. Compared to existing solutions, when a single receiving channel with a single directional antenna is used and space scanning is performed by rotating the UAV, the proposed approach with a multi-antenna system will reduce the time for azimuthal directions scanning.

Method of Group Coding of Infrared Images in Spectral-Wave Space

V. V. Barannik — 2025-03-30

The main features of the construction of intellectualized services for the exchange of infrared images (IRI) are considered. Namely, the possibility of obtaining informative meta-information. Such information may include: class and state of objects of interest, identification of image fragments by their level of informativeness.

The use of meta-information as a result of intellectualization is possible in a wide range of applied tasks. In particular, those that are solved using unmanned on-board systems. Some of these tasks are: monitoring of dynamic objects of interest, autonomous guidance of on-board complexes. In the process of performing the specified tasks by on-board complexes, decision-making is possible in the following modes: manual, autonomous, automated. However, there are conditions in which a hybrid variant of decision-making is possible. In this mode, at some stages of the decision, the on-board complex can be in an autonomous state, and at others in an automated state. Among the conditions that have an impact on the choice of mode: the presence of information conflict, crisis situations, the use of swarm technologies.

Taking into account the modes of use and tasks performed by on-board complexes, the requirements for the completeness of information are increasing (increasing the number of frames, limiting distortions, increasing the number of pixels for describing objects). The consequence of their compliance will be an increase in the information load on information and communication systems. Therefore, a contradiction appears between the requirements for quality characteristics: speed of information delivery, integrity of IR frames. Therefore, a scientific and applied task is relevant, which concerns the improvement of the quality characteristics of the provision of intellectualized information services based on the sources of IRI in applied tasks using on-board complexes. As a result of the analysis of modern technologies for solving the given problem, such as PNG and JPEG 2000, the following shortcomings were revealed: high computational complexity, introduction of significant distortions to the semantics, low efficiency in segments with a high number of heterogeneous objects. Therefore, the objective of the article's research is justified: the development of a method of group coding of data in the spectral-wave space.

The article describes the stages of method development, which begin with the decomposition of the IRI into a hierarchical structure of segments and minisegments. This allows to localize the homogeneous areas of the image. The resulting segments are further transformed into the spectral domain and spectral-group coding is applied, which allows to reduce the bit volume. An experimental evaluation of the developed method was carried out on the basis of the Open Turbulent Image Set (OTIS), which includes PNG images with different levels of informativeness. It was possible to reduce the bit volume of images by an average of 37%. In addition, a comparative analysis of the coding of 16-bit images with the existing coding method, which is used in the modern JPEG 2000 format, was conducted. Where it was shown that the developed method has an advantage in the compression ratio by 25%.

Electrical Impedance Mathematical Modeling of Piezoceramic Disc Oscillating in Wide Frequency Range (Part 3. High Frequencies)

C. V. Bazilo — 2025-03-30

This paper discusses the results of mathematical modelling the electrical impedance of a piezoceramic disk oscillating in a wide range of high frequencies. The study aimed to create a mathematical model that would incorporate geometric, physical, and mechanical characteristics of the material to assess the behavior of the disk under conditions of electromechanical resonance and antiresonance. The research particularly focused on the influence of radial and axial displacements of material particles on the frequency dependence of the mechanical quality factor and electrical impedance of the disk. Even more closely, this research scrutinizes specific effects characteristic of the high-frequency mode, in order to increase the accuracy of modeling and ensure optimal technical characteristics of the devices. The mathematical model developed in this paper serves as a tool to obtain estimates for the frequency dependence of the mechanical quality factor and the dynamic electrical capacitance in real conditions, in particular, by including energy losses due to viscous friction into the calculations. Numerical calculations confirm the high correlation between theoretical and experimental data (with the discrepancy lower than 3^.10^-3), which proves the model usable for designing piezoelectric devices. In particular, it was found that the frequencies of electromechanical resonance and antiresonance are virtually independent of the radial displacements of material particles and are determined by the axial components solely. In addition, the calculation model provides the ability to assess the electrical impedance in the high-frequency range with an accuracy that meets modern requirements for the design of functional piezoelectric devices. The results obtained have practical significance for developing precision elements for military equipment, high-precision sensors, ultrasonic generators, medical diagnostic devices, and other technological systems that function with piezoelectric materials.

Optimization Scattering Parameters of Optical Filters With Whispering Gallery Mode Resonators for Interleaver Building

A. A. Trubin — 2025-03-30

The frequency dependences of the scattering matrices of known types of optical filters, built on coupled Dielectric Resonators (DR) with whispering gallery oscillations, located in one or more transmission lines taking into account several frequency bands, are considered. New electromagnetic models of notch and add/drop filters of various types, which consist of one and two optical resonators with degenerate types of natural oscillations, have been built. The found solutions are used for calculations and analysis of frequency dependences of filter scattering matrices in several excitation bands of the structure's of resonators. Examples of the calculation of frequency dependences of scattering matrices for the most common structures are given, which can be found as practical relationships when building interleavers. The frequency dispersion characteristics of several types of filters consisting of one and two dielectric resonators were calculated. The frequency dependences of the scattering matrices of two most common types of filters made on the basis of coupled DRs located in parallel between two optical transmission lines are investigated: laterally coupled add/drop filters; parallel-coupled add/drop filters; twisted double-channel SCISSORS. The possibilities of the proposed method are demonstrated on examples of calculation of the dispersion matrices of add/drop filters, taking into account several frequency bands, which can be used to build interleavers. The effect of oscillations of resonators neighboring in frequency on the characteristics of filters was analyzed. Constructed electrodynamics’ filter models are the basis for calculating and optimizing the characteristics of a wide class of elements of the newest ultra-high-speed optical communication systems.

Development and Research of Three-Channel Power Divider for the Decimeter Range

S. Ye. Fabirovskyy — 2025-03-30

The work is devoted to the development and research of a three-channel decimeter range power divider. Power dividers are widely used in all branches of radio electronics and wireless communication systems, in particular in radio communication systems, radio monitoring systems and others. At the first stage of research, a three-channel divider was calculated based on the Wilkinson scheme, implemented on quarter-wave line sections. To minimize losses in the divider, air-filled coaxial line sections were used for its implementation. The ballast resistance system is implemented according to the triangle scheme, which made it possible to minimize its parasitic inductance. The expansion of the operating frequency band is achieved by using a two-stage scheme with an additional quarter-wave line section. At the second stage of the research, the parameters of the developed divider were simulated in the Micro-Cap 12 program, which is currently freely available. For this purpose, the serial parameters of all line sections of the divider were calculated. The simulation showed that in the range from 350 MHz to 550 MHz, the isolation between the channels is no worse than -23.2 dB, and at the central frequency – no worse than -40 dB. At the third stage, a research of the implemented experimental prototype of the three-channel divider was carried out. As the research showed, the transmission coefficient from the input to any of the output channels of the divider in the entire operating frequency band is no worse than -4.8 dB, and the reflection coefficient from the input is no worse than -20 dB, which indicates its high efficiency. The isolation between the channels at the boundary of the operating range is no worse than -22 dB and is heading to -40 dB in its central part. The results of the experimental research coincide well with the modeling results in the Micro-Cap 12 program, which confirms the reliability of the numerical calculation and the correct choice of the divider model.