Radio Equipment Research Articles

Methodology for choosing the optimal layout of multilayer printed circuit boards taking into account external mechanical influences

Formulation of the problem. radio-electronic modules on multilayer printed circuit boards (PCB) are characterized by an extremely complex design. When creating such modules, it is necessary to take into account, often extremely contradictory, requirements for the placement of components on the surface, taking into account thermal criteria, requirements for vibration strength and electromagnetic compatibility. Special-purpose radio equipment is often placed in blocks of a "cassette" design, which has a feature in fixing the PCB. Unlike conventional printed circuit boards, in this design, the PCB can only be fixed at the edges, so the placement of components, especially those with a large area, for example, such as microcircuits in BGA, QFP, QFN, PLCC packages, must be given great attention, as this affects mechanical strength and performance of the device. Purpose. Improving the efficiency of the design process of radio-electronic modules by rational placement of components on the PCB of a "cassette" design. Identification of areas with the highest mechanical stresses and deflections. Results. It was found that on the PCB of a "cassette" design, when it is fixed only around the perimeter, there are areas with increased deflections, where the installation of components with a large area is undesirable, since this leads to the destruction of the solder joint and the failure of the device. The board can be conditionally divided into nine areas with an aspect ratio of a/4 and b/4, where a, b are the length and width of the board. Experimentally, the most loaded areas of the MPP and areas that have the least impact on the component during external vibration were identified. Practical significance. A method for placing components on the PCB of a "cassette" design is proposed, which makes it possible to reduce the negative effects of external vibrations and static loads.

Design of Normal Mode Helical Antenna for Seawater Application

To overcome the substantial propagation loss in the ocean, a low frequency band should be chosen when contemplating radio wave communication.Then, the antenna used at the portable radio equipment should be very small compare to the wavelength. For the miniaturized antenna, the normal mode helical antenna(NMHA) is suitable because of achieving high efficiency. In this paper, design method of NMHA in the seawater condition (r=81, =4) is explained. The frequency bands of 100MHz and 15MHz are selected. The self-resonant structures are determined based on the theoretical equation. Electrical characteristics such as resonant frequency, input impedance, VWSR and antenna efficiency are obtained through simulation by FEKO simulator. Electromagnetic simulation model is formed by taking into account the practical experimental condition. At 100MHz and 15MHz, resonances are ensured for antenna diameter lengths of 6.83 cm and 12.2 cm respectively. Input resistance of 27.15and 94.14, antenna efficiencies of -14.88dB and -26.27dB are achieved at 100MHz and 15MHz respectively.

Reliability control of a thermoelectric cooler with changes in ambient temperature

The paper presents the development of method of thermoelectric system reliability indexes control for providing thermal modesof radio electronic equipment, based on thermoelectric coolers medium temperature variation. A mathematical model for investigating influence of the environment temperature variation on the reliability performance of a single-cascade thermoelectric cooler at a given temperature level of cooling, thermal load, geometry of thermoelement branches for different characteristiccurrent operating modes is considered. The results of calculations of the basic parameters, reliability indices, dynamic characteristicsand the analysis of dependences are given for revealing the peculiarities of control processes. It is shown that decreasing the medium temperature at a given chiller design decreases the operating current, increases the cold-productivity, and decreases the time of reaching a steady-state operating mode for various characteristic current operating modes. The time to steady-state operation decreases from the minimum failure rate to the maximum cooling capacity at a fixed medium temperature. The minimum steady-state operation time is ensured in maximum cooling capacity mode. Reduction of such significant for control indices as the amountof consumed energy for different characteristic current operation modes, required heat dissipation capacity of the radiator, time of reaching the steady-state mode is noted. Analysis of research results has shown that it is possible to control indicators of reliability of a single-stage cooler of a given design by changing the medium temperature by changing the value of operating current. A change in the medium temperature of the thermoelectric cooler due to an external supporting device makes it possible to vary the reliability indices and to find a compromise between the reliability, dynamics and cooling capacity of the thermal mode support system.

Recolha de informações sobre o cio em bovinos utilizando a internet of things

ABSTRACT Monitoring the movements of ruminant animals is one of the most challenging tasks. In animals that act according to their habits, it is difficult to label such movements and transfer them to farmers. Monitoring and recording the movement and behavior of animals on a farm is an adopted method for successfully determining the duration of the estrus cycle in ruminant animals. The Internet is a technology that offers remarkable solutions for such applications. The aim of this study is to determine the hourly step counts and to find the estrus period in the most accurate way with a circuit design applied to the ankles of animals using an IoT-supported microcontroller. The data is transferred to the web environment wirelessly and monitored via wi-fi communication signals. This wireless wearable and network equipment determines the step count and monitors the animal's abnormal body temperature. An IoT-supported microcontroller provides wireless communication, high-speed data transmission, and low power consumption. Insemination was ensured by testing different animals on the application farm. The data is monitored in real-time, and the system gives an alert. Low cost, high reliability, and being able to be watched over the internet are the advantages of the system. This study helped develop new techniques and provided a low-cost proposition for testing wearable technologies on animals.

Detection and analysis of Wi-Fi signals for address direction finding

Statement of problem. The active use of wireless technologies requires the development of radio equipment that monitors devices and data transmission networks and, in particular, wireless local area networks of the 802.11 standard (Wi-Fi). The need to identify unauthorized access points and subscriber devices of these networks, including their bearing and localization, is an urgent task of radio monitoring services. Correlation-interferometric direction finders based on a two-channel radio receiving equipment cyclically connected to various pairs of elements of a multi-element antenna system are an effective tool for bearing radio signals. For the direction finding of packet radio signals, direction finders accumulate time samples from different antenna pairs over long time intervals; joint processing of these data allows determining the direction of arrival of radio signals. However, in the frequency range of transmission of signals of the IEEE 802.11 standard, many sources carry out parallel transmission of information in the time-sharing mode, therefore, the direct accumulation of samples entails mixing and combining data generated by different sources. This causes gross bearing errors and requires the development of new ways of joint identification and bearing of packet radio signals. The purpose of the work is to propose a method for determining the identification features of access points and subscriber devices of Wi-Fi networks, which allows combining fragments of data samples when bearing radio sources. Results. The presented method of address bearing, focused on signals of the 802.11 standard, allows detecting OFDM signals, identifying access points and subscriber devices of the local network and forming an estimate of the direction to these sources of radio emissions. Practical importance. The use of address bearing of Wi-Fi network devices increases the functionality of existing analyzers. The presented method of address bearing is implemented based on the mobile direction finder ARTICLE-M [1], which is used in search and localization systems of unauthorized sources of radio emissions.

Mobile EEG systems for alpha neurofeedback and anxiety control

The present research is devoted to the study of the relationship between the oscillations of the electroencephalography (EEG) bands and the level of anxiety among sixteen youth athletes aged 17–21 using a mobile EEG system. The study explores the oscillations of brain waves in eyes-open and eyes-closed conditions at rest. The EEG was recorded using a wireless EEG Headset System with dry non-contact EEG sensor electrodes designed by NeuroSky, a ThinkGear module, and a MindCap XL headband. The results of the study demonstrated statistically significant differences between eyes-open vs. eyes-closed conditions in the alpha band in the prefrontal cortex (p≤0.006). While the correlation between the alpha band and the state of anxiety in the prefrontal cortex demonstrated a statistically significant linear relationship with the negative slope in the eyes-closed condition (p≤0.029). The data derived from single-channel wireless system equipment demonstrated results that are close to those recorded by conventional lab-based equipment. The different nature of the interrelation between the EEG alpha band oscillations in the prefrontal cortex, depending on the position of the eyes and the level of anxiety of youth athletes, can reflect its relationship to the "inner" world of the individual and is a plausible neurobiological index of anxiety. These findings encourage the application of the portable EEG system for the research of brain functions. Even more, that device may be used for alpha neurofeedback for anxiety in closed-eye conditions.

Method of assessment of energy intensity of public communication radio equipment with software adjustable working frequency for determination of interruption protection indicators

The ability of modern departmental communication systems to perform tasks in conditions of radio-electronic suppression by the enemy characterizes their immunity to interference. It is known that the interference protection of radio equipment in conditions of enemy radio reconnaissance and electronic suppression can be described by a set of probability indicators that characterize its secrecy (energy) and interference resistance. Secrecy (energy) is the ability of departmental communication systems to counteract the enemy's radio reconnaissance means, which are aimed at detecting the fact of the departmental communication system's operation, determining the parameters of its radio emissions, intercepting information for further deliberate radio-electronic and electromagnetic interference. One of the methods that significantly increases the secrecy of departmental communication systems is the use of signals with software-defined frequency conversion. These signals are a set of radio pulses (signal elements) whose frequencies change over time according to the law of pseudorandom sequence. The enemy searches for and detects the elements of these signals in a wide frequency band. This search is carried out under conditions of partial a priori uncertainty regarding their spectral-time structure using panoramic receivers. It should be noted that the basis of the radio reconnaissance means of the world's leading states is Fourier processors, which perform Fourier transforms from the implementation of a set of input signals. When designing and developing methods for interference protection, the problem of evaluating their energy stealth arises. Known research results and existing methodologies allow for a simplified assessment of the energy stealth of radio equipment with software frequency hopping under time constraints for decision making and do not take into account the peculiarities of the construction of modern panoramic analysis tools. In particular, the known methodologies do not take into account the peculiarities of the process of frequency-time searching for elements of such signals in a wide frequency range using panoramic receiving devices based on the complex application of different types of Fourier processors, the order of spectral-time processing of signal elements at the output of Fourier processors, requirements for their threshold sensitivity and dynamic signal range. Therefore, the article proposes a methodology for evaluating the stealthiness of communication systems with software-defined frequency tuning to determine the indicators of interference protection based on Fourier processors in the conditions of the opponent's use of modern radio-electronic intelligence tools.

Implementation and evaluation of low-speed speech compression LPC and MELP algorithms

Abstract— Currently, the design of a speech signal compression module that responds to low speed but still ensures signal quality for communication devices is a topic of interest for research. LPC (Linear Prediction Coding) and MELP (Mixed-Excitation Linear Prediction), two common approaches, are extensively researched and used, particularly in the vocoder of radio communication equipment like HF or VHF equipment. Implementing security solutions for these devices are challenging due to the crucial role played by the vocoder in signal processing prior to encryption. The paper first analyzes the two algorithms LPC and MELP and implements them on the current popular hardware technologies ARM and DSP to give an evaluation direction when choosing technology to serve the design of vocoders. There are many different methods of speech quality assessment in this paper, the PESQ method according to the ITU-T P862 standard was used to evaluate the results of the implementation of the proposed algorithms. The results show that the quality of the compression rate reduction of about 2 kbps is still satisfactory, and dedicated DSP technology for better speech quality results is a basis for helping vocoder device developers choose the right hardware technology when designing products.

Variant of determining the technical condition of an electrolytic capacitor by contactless method

In the course of the full-scale war in Ukraine, the defense forces began to receive radio-electronic weapons from partner countries. The samples of weapons that are provided are mostly not new and have a certain service life and (or) shelf life. As a result, the issue of diagnosing the technical condition of such samples became more acute. The article provides a variant of determining the technical characteristics of one of the low-reliability radio electronic components (electrolytic capacitor) of modern pulsed power supply units of radio electronic equipment. Practical methods and measuring devices for diagnosis and typical problems that have to be faced during work on determining the technical condition of the control object are considered. The main physical properties are described, which are the basis of the proposed method of determining the technical condition and the presented equivalent circuit of the diagnostic signal sensor. Calculations of empirical studies and assumptions expressed in previous works of the authors have been mathematically confirmed. The presented method is based on the use of a non-contact induction method. The determination of the technical condition of the radio-electronic component is carried out on the basis of the analysis of the output signals of the functional nodes that contain this component. The use of the proposed method requires the availability of a reference signal (response to the test signal) with which the signal obtained during the test is compared. Based on the potential effectiveness, informativeness and safety of the proposed method, the expediency of a non-fundamental change in the design of the control object is substantiated, in order to effectively apply the proposed method both directly in the blocks of mounted boards and circuits and on test stands.

Design and fabrication of a super-wideband transparent antenna implanted on a solar cell substrate

In this study, an antenna with transparent super wideband CPW technology has been designed and built with the combination of solar panels for use in wireless communication equipment and systems that require mobile power. The transparency value of the antenna is 63.3%, which is an acceptable value for the optimal use of sunlight. The proposed antenna was designed and measured on a plexi-glass substrate with a dielectric constant of {{varvec{upvarepsilon}}}_{{varvec{r}}}=4.4 and various thicknesses, the proposed antenna was designed and measured. The copper sheet has a high electrical conductivity and therefore it was selected for the antenna's radiating component as compared to earlier techniques that employed metal oxide. All simulations were done with CST microwave studio software and frequency domain solver. The results indicated that the antenna's operating frequency ranges from 2 to 32 GHz. The results of the computations indicated that the antenna's peak gain and peak efficiency are 8.1 dB and 90%, respectively. Various multiple-input and multiple-output (MIMO) performance parameters, including the envelope correlation coefficient (ECC), diversity gain (DG), average effective gain (MEG), total active reflection coefficient (TARC), and channel capacity loss (CCL), were analyzed to demonstrate the antenna's performance.

Tkachenko Methodology for building radio relay lines based on the use of geospatial information

When planning and organizing communication using modern military digital radios, a crucial and relevant task is to ensure the maximum possible communication range while providing the necessary speed and quality of information transmission. The main factors determining the possible communication range of modern military digital radios, in addition to their characteristics, are the terrain relief, buildings, and vegetation. Additionally, existing height objects in the area, such as communication operator towers, can be used to organize radio relay communication. An analysis showed that existing methods and specialized software can be used for certain calculations of signal levels, but they do not always take into account all necessary technical parameters of radio equipment and additional geospatial information. Moreover, the existing software is not designed to construct multi-interval radio relay lines while considering additional geospatial data. In constructing radio relay lines, there is often a situation where one interval cannot provide communication with the required quality. This situation calls for planning a radio relay line using relay stations. The choice of the location of relay stations depends on many factors, including the possibility of establishing communication, minimizing the number of relays, geospatial information regarding the terrain relief, and the presence of the necessary infrastructure (buildings, power supply, anchor points, towers, etc.) in the area. The article proposes a methodology for constructing radio relay communication lines based on calculations of signal levels while considering geospatial data. This methodology allows analyzing individual radio relay intervals for constructing multi-interval radio relay lines. The software implementation of the developed methodology allows creating software for calculating radio relay lines with the necessary input data and geospatial information regarding the terrain.

DEVELOPMENT OF THE COMPLEX LABORATORY WORKS FOR RESEARCH DIGITAL TELEVISION AND MOBILE COMMUNICATION SYSTEMS BASED ON SDR TECHNOLOGY

Abstract. Recen t decades have marked by revolutionary changes, including the emergence of software-defined radio equipment (SDR). However, there is virtually no training in this area, which does not allow for the full realization of the benefits of new, more advanced communication systems. Therefore, this work aimed at solving this problem. It presents the results of the development of a set of laboratory work on modeling new generations of mobile communication and digital television systems implemented using SDR technology and the methodological instructions necessary for students to perform these works.

Design and Development of Three Phase Detuned Filter Reactor for Reduction of Harmonic Distortion in Power Systems

Harmonics refers to a form of electrical distortion that can adversely impact power systems, electrical equipment, and the overall quality of power supply. The presence of non-linear loads, such as electronic devices, can cause the current waveform to deviate from the ideal sine wave, resulting in higher frequency currents that are multiples of the fundamental frequency. These distortions can lead to several negative effects, such as reduced power factor, increased energy losses, equipment overheating, and electromagnetic interference. These, in turn, can lower system efficiency, increase energy consumption, and escalate equipment maintenance costs. Several approaches have been developed to address the adverse effects of harmonics, such as the use of filters, capacitors, and other reactive components. These techniques aim to minimize harmonic distortion and improve power supply quality. This paper examines the effectiveness of a 1kVAr detuned reactor in mitigating harmonic distortion in power systems and electrical components. The detuned filter reactor reduces the harmonic distortion actively. It does so by monitoring the harmonic content of the power and injecting a counteracting current to cancel out the harmonic frequencies, creating a subtle "detuning" effect that reduces harmonic distortion. Detuned filter reactors find extensive application in radio and audio equipment, among other fields.

OPTIMAL SIGNAL-CODE CONSTRUCTIONS FOR INCREASE EFFICIENCY OF 5G AND 6G MOBILE INFOCOMMUNICATION RADIO SYSTEMS

The article discusses methods of increasing the efficiency of information communication radio systems of mobile communication, which includes increasing spectral efficiency and energy efficiency when used for telecommunication radio equipment. A comparison of block error coefficient values for f-OFDM, W-OFDM and OFDM methods with mixed numerology of uplink and downlink subscriber channels of access to information resources of the telecommunications network was made. As a result of the study of compression methods using several carriers, the dominant compression method for mobile communication systems, in particular, the CP-OFDM method due to its high efficiency of spectrum use, scalability and flexibility due to the introduction of a cyclic prefix, has been determined. It is proved that the CP-OFDM compression method is free from the Doppler range shift problem, thus the range and Doppler shift estimations can be considered as independent tasks in CP-OFDM. In addition, CP-OFDM parameters such as carrier distance, guard interval size, frame length, and pilot shape can be tailored to optimize the performance and robustness of detection and data transmission. However, such advantages are based on perfect synchronization (time and frequency) between the transmitter and receiver – although perfect synchronization may not be possible, especially for bistatic scanning, where the transmitter and receiver of the scan signal are not adjacent. In this case, the cyclic prefix may not provide any advantage for quality scanning, and multiple unprefixed waveforms may be considered. The main disadvantage of rejecting the prefix is the difficulty of data detection (due to intersymbol interference), which must be eliminated. Another important challenge for scanning, where energy efficiency is extremely important, is the large PAPR of multi-carrier (prefixed or unprefixed) signals. Single-carrier compression methods, which are based on the expansion of the code area of common radar signals and communication, in which the radar characteristics are affected by sequence autocorrelation, have been studied. However, the long spreading code, which leads to good autocorrelation, reduces the spectrum utilization efficiency for communication systems. In this case, the estimation of the Doppler effect is not trivial and requires more complex algorithms. The justification of the choice of the signal modulation scheme in 5/6G radio systems has been made.

Influence of the Heterogeneity of Spatial Distribution of Peripheral Radio Equipment of 4G/5G Networks on the Level of Electromagnetic Background Created in Buildings

Known results of studies of the radio frequency electromagnetic background generated in buildings by electromagnetic radiation from the peripheral equipment of 4G/5G mobile communications , including equipment for massive machine-type communication /Internet of things ( mMTC / IoT ) and user’s devices for wireless telephony and data transmission , are based on the use of a model of uniform random distribution of this equipment over the building internal space . The adequacy of this model for the analysis of a number of 4G/5G scenarios is questioned due to the fact that , excluding user’s devices , the main part of the mMTC / IoT peripheral radio equipment located in buildings is distributed along the walls of the premises with a tendency to concentrate them near the intersections of flat surfaces of walls , floors and ceilings . Paper presents the results of comparative estimates of the average intensity of electromagnetic background inside building for different types of distribution of the set of point sources of RF electromagnetic fields over the building interior space : for their uniform distribution over internal space and for two types of heterogeneity of this distribution : for uniform distribution of sources over building internal surfaces and with their uniform distribution along the lines of intersection of these surfaces . Results of this analysis indicate a relatively small effect of the considered types of heterogeneity in the spatial distribution of radiation sources on the estimates of the electromagnetic background average intensity created by these sources inside the building , when using a technique based on the representation of the internal space of a building as a set of solid angles , which internal space separate sections are characterized by the constancy of the sources average space density and by the average conditions for radio waves propagation in the direction of the observation point .

Cable Coupling Characteristics of Wireless Network Convergence Nodes by Transient Electromagnetic Fields in Intelligent Substations

Switching operations in intelligent substations generate a wide range of extremely strong and asymmetric transient spatial electromagnetic fields, and this complex transient electromagnetic field can have a coupling effect with the wireless network sink node equipment cables. We conducted a study on the networking method of wireless network equipment in smart substations and analyzed the types of sink node cables used. In the GIS room of the 110 kV GIS smart substation, the transient spatial electromagnetic field generated by switching operation and the transient induced current of the sink node cable under different operating conditions were tested and obtained, and the time domain and frequency domain comparative analysis was performed. A near-field coupling model of the asymmetric and non-uniform cable transient spatial electric field at the sink node is established, and the validity of the model is verified by comparing and analyzing the measurement and simulation results. The results of the study can provide a reference for transient electromagnetic disturbances in 110 kV GIS intelligent substations and contribute to improving the reliability of wireless network equipment operation.

The Influence of the Socionic Characteristics of a Pilot on the Features of Perception and Interpretation of Displayed Flight Instrument Information

The article continues a series of papers by the authors of the results of the study on perception and interpretation by a pilot of visual information provided by flight instruments. The data presented refer to experiments conducted in 2021–2022 with a sample of 50 cadet pilots. According to V. A. Sychev, the wellknown aviation professor, in the piloting technique, perceptual errors are most common. Among many flight instruments important for piloting an aircraft, there is one whose influence on the «Loss of control in-flight» (LOC–I) problem is the greatest – this is the attitude indicator. Several catastrophes are associated with perceptual errors of the readings of attitude indicators. One of the most tragic accidents of this kind was the crash near Perm on September 14, 2008, of a Boeing‑737 aircraft.The paper presents the results of a comparative study carried out to identify individual differences in perception and interpretation by tested cadet pilots of the roll indications on the attitude indicator with the «inside-out» and «outside-in» display options. During task performance, the participants were presented with a sequential series of images in the form of slides with roll indications of the attitude indicator with different display options. The experiment was carried out using a stationary Eye Tracker Tobii REX device. The analysis and processing of the data obtained was carried out using a special computer software developed by A. P. Plyasovskikh at the All-Russian scientific Research Institute of Radio Equipment. The participants to the experiment underwent also psychodiagnostics using Keirsey and MM‑1 socionic tests. Results were subject to mathematical processing with correlation analysis and G-sign test.The arguments given by some authors in favour of the «outside-in» version of the indication were fully confirmed since the number of errors when determining the side of the roll on the «inside-out» display of the attitude indicator turned out to be seven times higher than on the «outside-in» display. The hypothesis that socionic characteristics are predictors of the pilot’s correct perception and interpretation of visual instrumental information has not been confirmed. It is possible that the absence of significant correlations was also influenced by the significant uniformity in the socionic characteristics of the surveyed persons.

The effects of etching time and hydrogen peroxide concentration on the ZnO/glass substrate

The purpose of the study is to determine the best technique for etching ZnO thin films. ZnO is deposited on the glass substrate using a radio frequency sputtering equipment. To etch the ZnO thin film, hydrogen peroxide (H2O2) concentrations of 10%, 20%, and 30% are utilised, with etching times of 30 and 60 seconds. The optical band gap is lowered after a specific quantity of etching, which shows that the film's crystallinity quality has improved. The impact of various ZnO thicknesses on the sample's optical properties is investigated using OPAL 2 simulator. In comparison to other ZnO layers of varied thickness, the OPAL 2 simulation shows that the 400 nm ZnO layer has the lowest transmission in the UV wavelength range.

О РАСЧЕТЕ РАДИОЯРКОСТНОЙ ТЕМПЕРАТУРЫ ГРУНТА ЛУНЫ

Microwave radiometers have proven to be useful tools for studying the thermal regime of the atmosphere and the Earth's surface. Similar devices were recommended for inclusion in the composition of scientific radio equipment designed to study other bodies of the solar system, in particular the moon. The degree of understanding of the physical foundations of the experiments and the accuracy of their theoretical description is the coincidence of the results of measurements and numerical simulation of radio brightness temperature. The paper discusses the mechanism for calculating this value, deriving a recurrent formula convenient for calculating the radio brightness temperature from the Moon's soil. The algorithm is built for flat-layered soil. The depth distribution profile of physical temperature and complex permittivity for this problem are a priori information.

Применение сверточных нейронных сетей для прогнозирования критической частоты fₒF2

Ionosphere has an important impact on the quality of radio communication, radar, and global positioning. One of the essential characteristics describing the state of the ionosphere is its critical frequency fₒF2. Its prediction provides effective modes of operation of technical radio equipment as well as enables calculation of the corrections needed to improve the accuracy of its functioning. Different physical and empirical models are generally used for fₒF2 prediction. This paper proposes an empirical prediction technique based on machine learning methods and observational history. It relies on a regression approach to the prediction based on the known daily quasi-periodicity of ionospheric parameters related to solar illumination. Algorithmically, this approach is implemented in the form of convolutional neural networks with two-dimensional convolution. The input data for the analysis is presented as two-dimensional solar time — date matrices. The model was trained on data from the mid-latitude ionosonde in Irkutsk (RF) and tested using data from several mid-latitude ionosondes: Arti (RF), Warsaw (Poland), Mohe (China). It is shown that the main contribution to the prediction value of fₒF2 is made by the data on the nearest few days before the prediction; the contribution of the remaining days strongly decreases. This model has the following forecast quality metrics (Pearson correlation coefficient 0.928, root mean square error 0.598 MHz, mean absolute error in percent 10.45 %, coefficient of determination 0.861) and can be applied to fₒF2 forecast in middle latitudes.