Intensity Of Radio Signals Research Articles

Influence of atmospheric turbulence on the spectral composition of the radio signal

Background. It is shown that it is necessary to study the effect of atmospheric turbulence on the spectral characteristics of a radio signal. Aim. The influence of atmospheric turbulence on the spectral fluctuations of the radio signal intensity and on the displacement of the spectral components of the radio signal has been studied. Methods. The research was carried out on the basis of an analysis of the relationship between two-wave and single-wave correlation ratios. Based on the solution of the differential equation for fluctuations of the eikonal amplitude of an electromagnetic wave and the use of the derived trigonometric ratio, a connection between the two-wave Fourier=spectrum and single-wave spectra is obtained. In this case, a single source of turbulence effects on the radio signal was used at the coordinate point of the radio wave propagation by introducing a new variable equal to the average value of the coordinates of the turbulence effect. To find the resulting double integral, one of the coordinates of the turbulent action is transformed into an angular variable. Results. The dependence of the relative dimensionless mean of square of the integral intensity of the radio signal fluctuations on the wave number of turbulent pulsations of the atmosphere at various displacements of the spectral wavelengths of the radio signal is found. Conclusion. It is shown that turbulence slightly distorts the spectral information essence of a propagating radio signal in various wavelength ranges.

Flickering of a radio-signal due to an atmospheric turbulence

Background. Turbulent fluctuations of the refractive index in the atmosphere lead to distortions during the passage of the radio signal. This can lead to distortion of the transmitted information due to the resulting fluctuations of the amplitude, phase and intensity of the electromagnetic wave that transmits the radio signal. Fluctuations in the intensity of the radio signal lead to flickering of the radio signal on the receiving antenna due to turbulent phenomena in the atmosphere, which are a complex multifunctional physical phenomenon. Aim. The problem of fluctuation of the intensity of the radio signal at the receiving antenna due to atmospheric turbulence is considered the flicker of the radio signal. This problem is currently extremely actual, because there is a tendency of active, negative interference in the process of high-quality transmission of the radio signal on the background of naturally caused turbulent fluctuations. Methods. A theoretical analysis of the passage of a radio signal through a turbulent atmosphere is carried out. The spatial correlation function of fluctuations in the intensity of the received radio signal due to atmospheric turbulence is investigated. Results. The concept of the radio signal flicker characteristic is introduced as the average value of a random variable over the cross section of the receiving antenna the dispersion of the logarithm of the radio signal power. A model of the occurrence of fluctuations in the case of two regions in the cross section of the receiving antenna with different levels of radio signal intensity is calculated. The correlation function for this model is found. Conclusion. Based on the Fourier-spectrum expansion of the two-point spatial correlation function of turbulent fluctuations of the refractive index, the dependence of the flicker characteristic of the radio signal on the wave number of turbulent fluctuations of the atmosphere is found. It is shown that the turbulence of the atmosphere has the greatest effect on the radio signal when the length of the electromagnetic wave is comparable to the scale of turbulent fluctuations.

A New Indoor Location Algorithm Based on Radio Frequency Fingerprint Matching

Indoor positioning technology plays an important role in the production and life of today's society. Modern people's clothing, food, housing, and transportation are increasingly closely related to Location Based Service. In this paper, an indoor location algorithm based on the radio frequency fingerprint matching is offered. In the offline phase, by deploying a small number of radio signal intensity location regions, the location selection mechanism is used to predict the location of mobile terminals, which can avoid the instability of radio frequency signals caused by time-lapse and the impact of changes in Access Point (AP) facilities. In the online stage, the location engine receives real-time Radio Frequency fingerprints and updates the fingerprint location by mapping time and equipment. Finally, several main localization algorithms are simulated and compared to the aspect of location accuracy. The proposed new method reduces the location error, improves the location accuracy by 1 to 2 meters, and achieves 100% within 2.5 meters.

Energetic Electron Precipitation Associated With Pulsating Aurora Observed by VLF Radio Propagation During the Recovery Phase of a Substorm on 27 March 2017

AbstractRecent studies suggest that electrons with energies up to several hundred keV precipitate into the atmosphere associated with pulsating aurora (PsA). It is debated the highest energy of precipitating electrons associated with PsA. Here we report for the first time that the energy extends to relativistic energies. PsA was observed by THEMIS all‐sky imagers during a substorm that occurred on 27 March 2017. Energetic electron precipitation was detected by very low frequency subionospheric propagation. We found similar time variations between the auroral intensity and perturbation of the received radio signal intensity when the PsA occurred on the radio path. The perturbation showed a short recovery time of ~2 s. The recovery time indicates relaxation from ionospheric modification due to energetic electron precipitation and depends on the stopping altitude of the electrons. The recovery time required a stopping altitude of 50–60 km and indicates that the PsA is accompanied by relativistic electron precipitation.

Wavelet analysis of the LF radio signals collected by the European VLF/LF network from July 2009 to April 2011

In 2008, a radio receiver that works in very low frequency (VLF; 20-60 kHz) and LF (150-300 kHz) bands was developed by an Italian factory. The receiver can monitor 10 frequencies distributed in these bands, with the measurement for each of them of the electric field intensity. Since 2009, to date, six of these radio receivers have been installed throughout Europe to establish a ‘European VLF/LF Network’. At present, two of these are into operation in Italy, and the remaining four are located in Greece, Turkey, Portugal and Romania. For the present study, the LF radio data collected over about two years were analysed. At first, the day-time data and the night-time data were separated for each radio signal. Taking into account that the LF signals are characterized by ground-wave and sky-wave propagation modes, the day-time data are related to the ground wave and the night-time data to the sky wave. In this framework, the effects of solar activity and storm activity were defined in the different trends. Then, the earthquakes with M ≥5.0 that occurred over the same period were selected, as those located in a 300-km radius around each receiver/transmitter and within the 5th Fresnel zone related to each transmitter-receiver path. Where possible, the wavelet analysis was applied on the time series of the radio signal intensity, and some anomalies related to previous earthquakes were revealed. Except for some doubt in one case, success appears to have been obtained in all of the cases related to the 300 km circles in for the ground waves and the sky waves. For the Fresnel cases, success in two cases and one failure were seen in analysing the sky waves. The failure occurred in August/September, and might be related to the disturbed conditions of the ionosphere in summer.

Influence of meteorological and wave processes on the lower ionosphere during solar minimum conditions according to the data on midlatitude VLF-LF propagation

The statistical characteristics of the intensity of VLF-LF radio signals transmitted from the midlatitude radio stations and recorded by the receiver at the Mikhnevo geophysical observatory (54.94°N, 37.73°E; Institute of Geosphere Dynamics, Russian Academy of Sciences) in 2007–2010 are analyzed. The experiments revealed strong variations in the intensity of radio signals during the deep solar minimum conditions, when the medium does not experience impacts from above associated with solar and geomagnetic activity. We relate the observed variations to the disturbances from below, which are caused by the meteorological and wave processes occurring in the lower atmosphere.

EFFECT OF WILDFIRE-INDUCED THERMAL BUBBLE ON RADIO COMMUNICATION

Horizontal roll vortex pairs are dynamical structures that transfer energy and emissions from wildfires into the atmosphere. The vortices form at the edges of an intense line wildfire and emulate two cylinders, which form two curvatures of a biconcave thermal lens. Wildfire plume provides a dielectric material for the dielectric lens, whose permittivity is influenced by the nature, quantity of constituents (e.g., potassium and graphitic carbon) and variation of temperature with height in the plume. The environment created by the plume is radio sub-refractive with an effect of spreading radio wave beams. A numerical experiment was carried out to quantify loss of Ultra High Frequency (UHF) radio signal intensity when high intensity wildfireinduced horizontal roll vortices intercept UHF propagation path. In the numerical experiment, a collimated radio wave beam was caused to propagate along fuel-fire interface of a very high intensity wildfire in which up to two roll vortex pairs are formed. Maximum temperature of the simulated wildfire was 1200 K. Flame potassium content was varied from 0.5–3.0%. At 3.0% potassium content, a vortex pair imposed a maximum radio ray divergence of 2.1 arcmins while two vortex pairs imposed a maximum divergence of 4.3 arcmins at the fuel-fire interface. The ray divergences caused maximum signal strength loss (in decibels (dB)) per unit path length of 0.154dBm−1 and 1.65dBm−1 respectively.

Rocket observations of the intensity of very low frequency noise above the ionosphere

Abstract The intensity of radio signals in the frequency range 0.5–12 kc s was measured during two rocket flights, one near midnight and one near noon. On both flights, whistlers were observed—22 at night and 122 in the day. Hiss also was recorded on both flights—at 2.8 kc s at night and at 800 c s in the day. No hiss or whistlers were observed on the ground on either occasion. At night the intensity of whistlers in the ionosphere was at least 750 times that on the ground and the hiss intensity was at least 180 times that on the ground. During the day the corresponding factors were 8000 and 10,000. These ratios are much greater than could be caused by absorption. They are probably due to total internal reflection in the low ionosphere, since VLF waves penetrate to the ground only if their wave normals are within a small cone about the vertical. It is concluded that it is impossible to deduce the intensity of VLF waves in the ionosphere from measurements made on the ground.

Experiments in Recording Radio Signal Intensity

The paper describes briefly the method of recording the strength of long-wave radio signals used at the Bureau of Standards and gives some of the results obtained. The curves shown indicate the great variability of the wave propagation both in regard to strength and the angle of incidence of the downcomning wave. This variability appears to be greater for transmission distances below 1000 km than for greater distances. An apparent connection is shown in certain cases between the night signal variations and magnetic storms. The observations seem to indicate that the downcoming waves are reflected (or refracted) from rapidly changing masses of ionized gas.