Range Of Radio Waves Research Articles

Atmospheric Noise Measurements in the Garden: Detecting Universalities in Inter-Spheric Waiting Time Statistics

Lightning flashes result in an instantaneous emission of electromagnetic (EM) waves that encompass a broad spectrum of frequencies in the domain of radio waves. The signature of these impulses in the region of the very low frequency (VLF) of radio waves and bellow are called spherics. These impulsive signals traverse great distances in the waveguide between the Earth’s ionosphere and its surface. Due to the abundance of lightnings the lower end of the EM spectrum is dominated by the waveforms of these emission. It is called atmospheric radio noise because of its origin. This article outlines a straightforward approach for capturing spherics activity within the VLF radio wave range. Employing data processing techniques, we pinpoint the timestamps of spherics within time series data. The distribution of inter-spheric times is analyzed across various detection threshold levels. Utilizing recordings spanning two distinct years and seasons, we replicate the established form of the inter-spheric time distribution described in the literature. Notably, we demonstrate that by rescaling the time intervals between spherics with the mean time for a specific recording and given detection threshold, the distributions collapse to a master curve. This universal pattern is accurately characterized by a single-parameter mean-scaled Gamma distribution. Additionally, we note the similarities in the distribution of inter-spheric times with patterns found in earthquake recurrence times.

Модели расчета распределения уровня мощности электромагнитного поля в системах подвижной радиосвязи для малых дистанций в летний период

The statement is substantiated that for the design of mobile radio communication systems at short distances up to 1 000 m, the main recommended calculation models have a significant error, since they were created for calcula-tions of long distances (as a rule, from 1 to 50 km) and have limitations in application. Due to the fact that at the present stage of development of mobile radio communication systems, the frequency ranges are in intensive research and use not only 900 and 1 800 MHz, but also 450-800 MHz sections, as well as from 2 100 to 6 000 MHz, which were not previously used for cellular communication systems, it is necessary to propose additional models necessary for the preliminary design of 3-5 generation systems in the range from 2 100 MHz. The range of radio waves in the ranges from 2 100 to 6 000 MHz is significantly reduced compared to the ranges of 1 800 or 900 MHz. The use of classical calculation models such as the Okumura and COST-231–Hata models at distances less than 1 km is characterized by significant errors and is not recommended by the authors of the models themselves for use at short distances. To solve this problem, new models have been developed for calculating the attenuation of radio signals designed to estimate attenuation at short distances.

Non-destructive methodology for crack detection using machine learning-assisted resonant sensor

Condition monitoring of structures built using metallic supports is a significant issue in structural engineering. Through this work, design, fabrication, and optimization of a dual-scale resonance-based microwave sensor is discussed for monitoring cracks developed over metallic surfaces. These sensors were initially simulated and later fabricated in micro-wave (4.59 GHz) and radio-wave region (418 MHz) for which the power attenuation and frequency shifts were observed. With the structure having crack depth of 2 mm, microwave sensor showed the power shift ∼24 %, while the radio-wave range sensors showed ∼9 %. The corresponding frequency shifts were 2.4 % and 0.85 %, respectively. The microwave sensor (power shift data) showed ∼280 % more sensitivity than the radio-wave sensor. By using dual scale, comprising of both frequency and power shifts, the microwave sensor classification was further improved to 99.72 %, as compared to their individual counterparts. A non-destructive crack detection system in microwave regime is hence demonstrated, which can be further explored for range of crack studies in metallic structures.

THE LONG-TERM OBSERVATIONS OF THE POWER COSMIC RADIO SOURCES ON THE RADIO TELESCOPE URAN-4 AT THE DECAMETER WAVE RANGE

The radio telescope (RT) URAN-4, located near the city of Odessa, started to work in 1987 as a component of the radio interferometric system URAN, which operates in the decameter range of radio waves and whose elements are placed in several points throughout Ukraine. The first successful VLBI observations of compact cosmic radio sources in the URAN system were carried out on the RT URAN-4–UTR-2 interferometer at the end of 1987. In the same period, a program was launched for regular observations of powerful cosmic radio sources 3C 144, 3C 274, 3C 405, 3C 461 at frequencies of 20 and 25 MHz in the radiometric mode. Later, several stages of modernization of radiometric equipment and systems for automation of observations took place. This made it possible by 2000 to switch to practically continuous radiometric monitoring of a group of these radio sources. Method of measuring and processing of the records of the radio sources passage through RT direction pattern, statistics of the observation records on time periods in dependence on the registration systems of the data obtained during more 35 years observations on the RT URAN-4 are considered in this paper. Some results are given which related to the study of the flux densities of the observing radio sources and ionospheric scintillation effect which is essential at the decameter wavelength range.

Attractive study of the physical properties of silver iron oxide nanoparticles for biomedical applications

Novel ratios of silver iron nanoparticles with the chemical formulas Ag2Fe2O4 with Ag/Fe ratio = 1/1 and Ag0.5Fe2.5O4 with Ag/Fe ratio = 1/5 were successfully synthesized using a flash auto-combustion technique at 400 °C. Structural properties were studied using XRD (x-ray diffraction), AFM (Atomic Force Microscopy), FESEM (Field Emission Scanning Electron Microscopy), and FTIR (Fourier transform infrared) analyses. The nanosize range determined from XRD analysis lies in 56.6–71.1 nm for Ag0.5Fe2.5O4 and Ag2Fe2O4 nanoparticles. The morphology was analyzed using AFM and FESEM to confirm that the particle size of both samples was spherical and nanosized with agglomeration. Fourier transform infrared (FTIR) analysis was performed to confirm nano-samples’ formation. Both samples were measured using a vibrating sample magnetometer to study their magnetism. By increasing the concentration of iron ions, the saturation magnetization (Ms) increased 5-fold for Ag0.5Fe2.5O4 nanoparticles compared with Ag2Fe2O4 nanoparticles. Moreover, there is a relation between saturation magnetization and antimicrobial activity, in which high (Ms) gives high antibacterial activity. Thus, Ag0.5Fe2.5O4 had a high (Ms) and high efficacy against the tested bacteria. However, Ag2Fe2O4 showed high activity against Candida albicans. Moreover, a high-frequency application was measured from the magnetic measurements, showing that both samples could be applied at a very high frequency (VHF) in the radio wave range. Finally, both samples could be antibacterial materials, particularly Ag0.5Fe2.5O4 nanoparticles. However, Ag2Fe2O4 nanoparticles are strongly recommended for antifungal activity against Candida albicans.

Noise Immunity of Single-Sideband Modulation Signals with a Controlled Carrier Level

Single-sideband modulation is actively used in the organization of communication through the ionospheric channel in the decameter range of radio waves. This is due to the fact that transmissions with single-sideband modulation make it possible to minimize the frequency band while maintaining the information transfer rate and at the same time increase the noise immunity of reception in relation to transmissions with amplitude and frequency analog modulation. At the same time, the widespread use of quadrature synthesis technologies has opened up new possibilities for the formation of transmissions with single-sideband modulation without the direct use of filtering procedures. An analysis of the implementation features of the method of quadrature synthesis of signals with single-sideband modulation showed that the introduction of an additional parameter into its procedures will allow you to control the residual level of the carrier wave, and thereby control the noise immunity of the reception. The opened opportunities made it possible to develop a method and a device for generating a single-sideband modulation signal with an adjustable level of the carrier wave that implements it. The technologies of quadrature synthesis of signals of amplitude modulation and single-sideband modulation with the suppressed carrier are considered both at the level of analytical modeling and using a standard quadrature modulator. The necessity of transition to the analytical form of representation of the modulating signal is substantiated. The role and place of the Hilbert converter in the formation of signals with single-sideband modulation are shown. Known technologies for generating single-sideband modulation signals with a stored pilot signal are considered. The possibility of controlling the value of the stored pilot signal at the level of quadrature synthesis procedures is substantiated. An analytical model and, based on it, a structural diagram have been developed that allow one to generate single-sideband modulation signals with an adjustable pilot signal level. The results of analytical modeling are demonstrated. The value of the provided energy gain as a result of regulation by the residual level of the carrier wave is calculated. Approaches to assessing the noise immunity of transmissions with single-sideband modulation are analyzed. An approach is proposed for calculating the bit error probability of SSB transmissions manipulated by discrete oscillations based on the results of energy redistribution between the carrier oscillation and the sideband, determined by the residual pilot signal level. Conclusions and proposals for the practical implementation of the results obtained are formulated.

Determination of frequency dependencies of deciles of the signal-to-noise ratio

The level of signal and interference in the decameter range of radio waves is subject to significant random changes, which affects the reliability of radio communications. The reliability of radio communication in the decameter range is determined by the ratio of the average signal level to the noise level at the receiver input to its permissible value, which, in turn, depends on the selected operating frequency. Also an important indicator is the standard deviation (standard deviation) of the signal-tonoise ratio at the receiver input. The latter is considered to be a constant value and is 14 dB. Nevertheless, according to experimental data, the standard deviation (RMS deviation) of the ratio of signal power to noise power at the receiver input in the decameter range may vary depending on frequency, which may affect the accuracy of communication reliability calculations.

Stanislavsky, A.A., Koval, A.A., Bubnov, I.N., and Brazhenko, A.I. Progress in the study of decameter-wave- length solar radio emission with Ukrainian radio telescopes. Part 2. (Invited paper)

Subject and Purpose. This part of the paper continues presentation of results of the solar radio emission studies performed with Ukrainian radio telescopes over the past 20 years. The importance is stressed of developing adequate instruments and methods for identifying the nature of decameter-wavelength radio emissions from the Sun. Methods and Methodology. The low frequency Ukrainian radio telescopes UTR-2, GURT and URAN-2 have been used in the project along with other ground- and space based instruments in order to achieve a comprehensive understanding of physical conditions in the solar corona. Results. Special methods and tools have been developed for studying radio frequency burst emissions against the background of strong interference. Unique data have been obtained concerning sources of sporadic radio emissions from the Sun, as well as the contribution from wave propagation effects and the impact of the ionosphere on the results of observations. The most significant observational and theoretical results are presented, obtained in the study of solar low frequency emissions over the past 20 years. Solar radio emissions are shown to be efficient sounding signals not for the solar corona alone but for the Earth’s ionosphere as well, which allows identifying its impact on the results of radio astronomy observations. Conclusions. The Ukrainian radio telescopes of the meter and decameter wavebands currently are unrivalled tools for investigating the Universe in the low-frequency range of radio waves. Owing to their advanced characteristics, they make a significant contribution to the progress of world’s solar radio astronomy.

GEORADAR AND RADIOIMPEDANCE DIAGNOSTICS OF THE SELENGA RIVER WATER AREA

The relevance of the work is determined by the fact that no radiowave methods have ever been used to study the water areas of rivers and lakes and their geoelectric sections within the Baikal natural territory (BNT) in winter time. The purpose of the research is to determine the electrical and geometric characteristics of the layered medium "ice – water – bottom soil" and the ice cover of the Selenga River on the BNT in the VLF-LF and VHF radio wave bands according to the data of instrumental radiophysical measurements by GPR and radio impedance methods, including the determination of the structure of the ice crossings over the Selenga River. Using the Selenga River as an example, consideration has been given to the results of combining VLF-LF and VHF methods of electromagnetic diagnostics of a layered medium in a wide range of radio waves (from tens of kilohertz to units of gigahertz). Radio impedance profiling and sounding in the VLF-LF bands with the IPI-300 equipment made it possible to determine the sub-bottom structure of the soil from the change in impedance and geoelectric section. GPR in the VHF band made it possible to differentiate the fine structure of the Selenga River in winter by thickness of snow, ice and water. The sounding involved the use of georadar "Oko-2" with antenna units "Triton" (central frequency 50 MHz), AB-400 (central frequency 400 MHz), AB-700 (central frequency 700 MHz), and AB-1700 (central frequency 1700 MHz). The thickness of ice of the road crossing in the Mostovoy microdistrict of Ulan-Ude city was 0.5–1.2 m – 0.1–0.2 m thicker than that beyond the road crossing. It was found that the presence of snow cover beyond the road crossing prevents the ice mass from freezing. Calibration sounding of ice with borehole drilling yielded ice dielectric constant ε=3.17. The specific electrical resistance (SER) of water from boreholes is 71–74 Ohm·m at a temperature of 1 °C. The methods used complement each other and provide a quantitative description of the object of research. The integration of various methods of radio wave diagnostics provides more detailed information on the structure of the layered medium "ice – water – bottom soil". The obtained results and the developed methods of radio impedance and GPR sounding and profiling of an inhomogeneously layered underlying environment in winter time can be used in engineering and geological surveys in the eastern and northern regions of Russia.

Оптимізація алгоритму формування рельєфу поверхні бортовим вертолітним радаром

The main advantages of helicopters include the ability to reduce altitude and flight speed, hover in the air, unscheduled landings, and low sensitivity to weather conditions. These advantages over the aircraft allow the use of helicopters for civilian and military purposes. Simultaneously, the problem of landing the helicopter on an unequipped area with unknown terrain in bad weather conditions, in low visibility, at night, and in smoky areas remains unsolved. This research optimizes the algorithm of terrain formation from a helicopter. To achieve this goal, the radio wave range is used, which allows to operate the system regardless of external conditions and lighting. The geometry of the problem assumes that the distance to each point of the surface is measured by the pulse method. In the bow of the helicopter, there are two antennas, which due to the spatial diversity form two patterns that overlap some areas of the underlying surface. The summary and differential channels are formed from the antenna outputs. During the formation of the input data, mathematical models of the probing signal and the received observations are given, considering the influence of the atmosphere on the propagation of waves and the internal noise of the system. A theoretical study of the optimal algorithm for forming the surface relief by on-board helicopter radar was performed within the method of maximum likelihood. The obtained analytical expressions help calculate the angular position of the pulse volume, which can then be used in the formation of the surface of the area to be landed. Because of the analysis, a structural scheme of the onboard sum-difference system of measurement of range and the angular position of the scattered radar pulses is proposed. The block diagram clarifies the principle of operation of the optimal algorithm and implements the construction of relief. In accordance with the developed algorithm, a simulation was performed, which resulted in angular positions in degrees. The obtained initial data prove the efficiency of the presented on-board radar for the formation of the underlying surface.

Improving the efficiency of the physical protection system for oil and gas facilities (by the example of trunk pipelines)

The article discusses the features of ensuring technospheric safety at oil and gas facilities (using the example of trunk pipelines) in the implementation of national interests. To achieve strategic goals, the developed structure of the physical protection system of trunk pipelines can be used to detect and prevent outside interference in their work, based on the use of passive seismic-analytical and active bioradioinformative methods for monitoring the security zone. An innovative approach is considered, which is based on the effect of the dependence of intruders’ own electromagnetic radiation on the strength of an external low-intensity electromagnetic field of the radio wave range. Its implementation in the creation of technical means provides high selectivity, initially assuming a response only to living organisms, as well as the possibility of classifying biological objects according to their most informative features in any natural and climatic conditions.

Demonstration experiment in the study of Fresnel diffraction

The article describes a methodology for studying Fresnel diffraction with the active involvement of students in discussing the results of a demonstration experiment. To create a clearly visible model of Fresnel zones, a centimeter radio wave range was chosen, in which the first zone is about 10 cm in size. This makes visible the created combinations of open and closed sections of the wavefront and allows students to predict the results of demonstrations. To maintain the cognitive activity of students, the method of creating and resolving educational contradictions, problem situations is used.

Bunch Expansion as a Cause for Pulsar Radio Emissions

Abstract Electromagnetic waves due to electron–positron clouds (bunches), created by cascading processes in pulsar magnetospheres, have been proposed to explain the pulsar radio emission. In order to verify this hypothesis, we utilized for the first time Particle-in-Cell (PIC) code simulations to study the nonlinear evolution of electron–positron bunches dependant on the initial relative drift speeds of electrons and positrons, plasma temperature, and distance between the bunches. For this sake, we utilized the PIC code ACRONYM with a high-order field solver and particle weighting factor, appropriate to describe relativistic pair plasmas. We found that the bunch expansion is mainly determined by the relative electron–positron drift speed. Finite drift speeds were found to cause the generation of strong electrostatic superluminal waves at the bunch density gradients that reach up to E ∼ 7.5 × 105 V cm−1 (E/(m e c ω p e −1) ∼ 4.4) and strong plasma heating. As a result, up to 15% of the initial kinetic energy is transformed into the electric field energy. Assuming the same electron and positron distributions, we found that the fastest (in the bunch reference frame) particles of consecutively emitted bunches eventually overlap in momentum (velocity) space. This overlap causes two-stream instabilities that generate electrostatic subluminal waves with electric field amplitudes reaching up to E ∼ 1.9 × 104 V cm−1 (E/(m e c ω p e −1) ∼ 0.11). We found that in all simulations the evolution of electron–positron bunches may lead to the generation of electrostatic superluminal or subluminal waves, which, in principle, can be behind the observed electromagnetic emissions of pulsars in the radio wave range.

Sub-band detection of small-sized objects during airspace sensing with ultra-short radio pulses

The possibility of ensuring the safety of flights of aircraft, such as helicopters, at low altitudes, where there is a high probability of unauthorized appearance of small-sized objects such as unmanned aerial vehicles, is being considered. The possibility of solving the problem of detecting such objects on the basis of radar soundings in the resonant frequency range of the UHF radio wave range is considered. Sub-band processing of the received signals is proposed, based on the division of the spectral definition area into sub-bands, for adaptation to the frequency response band and noise filtering. The mathematical apparatus of sub-band signal analysis using sub-band matrices has been developed. An optimal solution to the problem of filtering responses in given sub-bands is obtained. A procedure for processing the received signals is given when making decisions about the presence of a response in a given sub-band. Estimates of the probabilities of erroneous decisions are given for a given probability of errors of the first kind.

Surface Impedance of the “Thick Ice–Sea” Structure in the Radio Wave Range from Very Low to Very High Frequencies

Surface Impedance of the “Thick Ice–Sea” Structure in the Radio Wave Range from Very Low to Very High Frequencies

THE SURFACE IMPEDANCE OF THE "THIN ICE - SEA" AND "THICK ICE - SEA" STRUCTURES IN VLF-VHF RADIO WAVE BANDS

To calculate the propagation of the electromagnetic field over the two-layer struc-ture "ice - sea", the areas of applicability of the impedance boundary conditions are determined depending on the thickness of the ice and the angle of incidence of the vertically polarized wave in the range of 0.01-420 MHz. The article examines the structures "thin ice - sea" and "thick ice - sea" (six models of ice cover). The ice thickness varied from 0.03 to 9 m. The results are needed to calculate the atten-uation function and the field level in the VLF, LF, MF, HF, VHF radio wave bands. It is shown that for the structure “ice - sea” it is important to take into account the dependence of the surface impedance on the angle of incidence for over-the-horizon radar systems in the HF radio wave range. In the VHF range the frequency bands are determined for ice 80 cm thick, in which the impedance boundary condi-tions are applicable.

Correction of age-related skin changes on face by the method of exposure to high-frequency currents of the radio wave range and autologous platelet-rich plasma: randomized study

BACKGROUND: In the literature, there are no scientifically based studies on the use of combination therapy using radio wave lifting and autologous platelet-rich plasma for the correction of involutional changes in the skin of the lower third of the face.
 AIMS: To determine the effect of complex therapy of involutional changes in the skin of the lower third of the face with minimally invasive radio wave lifting using a cannula electrode and platelet-rich autoplasma using non-invasive diagnostic methods.
 MATERIALS AND METHODS: Examination and treatment of 55 healthy women of Slavic appearance with involutional changes in the skin of the lower third of the face were carried out. Group № 1 patients received radio wave lifting therapy (n=28) and group № 2 patients received combined therapy with radio wave lifting and autologous platelet-rich plasma (n=27). The study was conducted from January 2020 to December 2020. To assess the condition of the skin, laser Doppler flowmetry, ultrasound sonography, and elastometry were used before and after the study. Clinical manifestations were assessed by an anthropometric method.
 RESULTS: The most pronounced changes were observed in the group where the combined method of radio wave lifting therapy with autologous platelet-rich plasma was used. The change in microcirculation was of a multidirectional nature, however, the average values were in the range of 8.8668.89 pf units, which is the normalization of trophic processes in tissues (p 0.05). When analyzing the conduct of ultrasound sonography, statistically significant thickening of the epidermis and dermis was noted, however, in patients of the second group, the thickening was more pronounced (p 0.0005). The change in the echogenicity of the dermis was of a multidirectional nature; by the end of treatment, the mean values were in the range of 10.511.3 units, which, apparently, indicates a more homogeneous structure of the dermis (p 0.05). Anthropometric indices (measurement of ptosis of the lower cheeks) decreased in both groups, which is related to skin lifting as a result of treatment (p 0.0005). The amplitude of tissue upward mobility decreased in both groups (p 0.0005). The amplitude of downward movement of tissues after therapy was of a multidirectional nature in both groups, which is possibly associated with the density of the dermis and indicates the normalization of collagen and elastin fibers (p 0.05). Elastometry indices (F0, R4, R6, R8) decreased, R2 increased in both groups, however, the dynamics was more pronounced in the second group (p 0.0005).
 CONCLUSIONS: Minimally invasive radio wave lifting in combination using a channel electrode with autologous platelet-rich plasma is an effective and safe method of treating age-related changes in the skin of the lower third of the face.

Properties of Electric Conducting Magnetic Composites in the Ultrashort Range of Radio Waves

A study is made of the radio-shielding and radio-absorbing properties of three-phase ECOM-P/graphite/paraffin composites in the ultrashort range of wavelengths. The effect the concentration of components of the radioabsorbing filler of a composite has on its dielectric permittivity, losses, and electrical conductivity is determined.

MODERN POSSIBILITIES OF HIGH FREQUENCY RADIO WAVE CURRENTS IN AESTHETIC MEDICINE

The radio wave effect on biological tissues is of great interest to dermatologists, cosmetologists, and plastic surgeons. The modern information about radio wave therapy of involutional changes of face and neck skin is shown. A literature review of the physical aspects of the high-frequency current of the radio wave range is presented. The thermal and oscillation effects of radio frequency (RF) on biological tissues are shown, the mechanism of these effects at the cellular level is described. Primary targets of high-frequency currents exposure in the skin, their effect on the physicochemical properties of collagen and unicellular organisms are described. The mechanism of pulsed and continuous radio wave technologies and the possibility of their use in medical practice are described. Types of minimally invasive and non-invasive electrodes, when the choice of electrode diameter determines the therapy of specific clinical cases, are shown. The multifunctional minimally invasive RF device Innofill with needle and cannula active electrodes is presented. The technical characteristics and exposure modes of the device are considered. The features of the cannula electrode and the possibilities of its use in solving various dermatological and cosmetic problems are highlighted. A histological study of a combined technique of the Innofill radio wave method with the filler based on hyaluronic acid, was performed. A change in the amount of collagen and elastin fibers was noted. The distribution of the filler in the tissues was evaluated after the injection of the filler based on hyaluronic acid, after 30 and 60 seconds of RF exposure and after 30 seconds of RF exposure in a tunnel technique with the formation of a collagen channel. Histological material was stained with hematoxylin-eosin, Masson and Van Gieson trichrome. High efficiency, safety and prolonged effect of this exposure were described.

About the nature of short-period fluctuations of seasonal thawing depth in tundra soils

The series of 20-year-long observations of seasonal thawing have been studied on CALM plots in Eurasia and North America. The short-term (2-5 years) fluctuations of the active layer are considered. Similarities and differences in seasonal thawing of tundra soils in circumpolar countries are noted. The dynamics of seasonal thawing is analyzed by the example of two CALM plots in the Chukotka Autonomous District. Time series of changes in the depth of seasonal thawing are described using the mathematical methods. The amplitude, frequency and periods of oscillations are determined for them. The comparative graphical and statistical analysis of climate and seasonally thawed layer variations allowed us to judge on the nature and degree of influence of meteorological factors on the depth of soil thawing. The problems of interpretation of intra-century fluctuations of climatic parameters and seasonal thawing are considered. It is concluded that the duration of the warm season affects significantly the depth of seasonal thawing. It is noted that ignoring the intra-century variations in the parameters of climatic and permafrost landscapes is the cause of inconsistency of judgments about climate change trends and forecasts of permafrost degradation.
 A new concept of “climatic year” was proposed as the conjugation of weather conditions for 2-3 years equally affecting the depth of thawing. The established statistical regularities in changing permafrost-climatic conditions can be used for the preparation of 3-5 and 10-15 summer weather forecasts. The use of the ratio of the average values of the amplitude to the period of short oscillations as an indicator of the stability of the roof of permafrost is justified.
 The hypothesis of the influence of solar and technogenic electromagnetic radiation in the radio-wave range on the degradation of underground ice of the active layer and Arctic ice is proposed.