Theory of the limiting polarization of radio waves emerging obliquely from the ionosphere

1971 ◽  
Vol 324 (1558) ◽  
pp. 369-390 ◽  
Keyword(s):  
Wave Propagation ◽  
Radio Wave ◽  
Free Space ◽  
Wave Solution ◽  
Oblique Incidence ◽  
Integration Method ◽  
Lower Ionosphere ◽  
Numerical Integration Method ◽  
Radio Waves ◽  
Full Wave

The polarization of a downgoing radio wave when it has emerged from the ionosphere into free space is called the ‘limiting polarization’. To calculate it for waves at oblique incidence and medium frequencies, a full wave solution of the electromagnetic equations governing radio wave propagation in an inhomogeneous anisotropic ionized medium is used. The numerical integration method and the appropriate boundary conditions are described and some results for typical ionospheric distributions are given. The underlying problem of wave coupling is briefly discussed and the concept of complex limiting height introduced to describe the position and thickness of the region in the lower ionosphere in which the limiting polarization is established.

scholarly journals Perspective Ground-based Method for Diagnostics of the Lower Ionosphere and the Neutral Atmosphere

2013 ◽  
Vol 22 (1) ◽  
Author(s):  
N. V. Bakhmetieva ◽  
G. I. Grigoriev ◽  
A. V. Tolmacheva
Keyword(s):  
Radio Wave ◽  
High Power ◽  
Relative Concentration ◽  
Spectral Characteristics ◽  
Lower Ionosphere ◽  
Internal Gravity Waves ◽  
Spatial Period ◽  
Neutral Atmosphere ◽  
Radio Waves ◽  
D Region

AbstractWe present a new perspective ground-based method for diagnostics of the ionosphere and atmosphere parameters. The method uses one of the numerous physical phenomena observed in the ionosphere illuminated by high-power radio waves. It is a generation of the artificial periodic irregularities (APIs) in the ionospheric plasma. The APIs were found while studying the effects of ionospheric high-power HF modification. It was established that the APIs are formed by a standing wave that occurs due to interference between the upwardly radiated radio wave and its reflection off the ionosphere. The API studies are based upon observation of the Bragg backscatter of the pulsed probe radio wave from the artificial periodic structure. Bragg backscatter occurs if the spatial period of the irregularities is equal to half a wavelength of the probe signal. The API techniques makes it possible to obtain the following information: the profiles of electron density from the lower D-region up to the maximum of the F-layer; the irregular structure of the ionosphere including split of the regular E-layer, the sporadic layers; the vertical velocities in the D- and E-regions of the ionosphere; the turbulent velocities, turbulent diffusion coefficients and the turbopause altitude; the neutral temperatures and densities at the E-region altitudes; the parameters of the internal gravity waves and their spectral characteristics; the relative concentration of negative oxygen ions in the D-region. Some new results obtained by the API technique are discussed.

scholarly journals A Novel Radio Wave Propagation Modeling Method Using System Identification Technique over Wireless Links in East Africa

2018 ◽  
Vol 2018 ◽  
pp. 1-7
Author(s):  
Solomon T. Girma ◽  
Dominic B. O. Konditi ◽  
Ciira Maina
Keyword(s):  
Wave Propagation ◽  
System Identification ◽  
Radio Wave ◽  
Free Space ◽  
Urban Areas ◽  
Radio Channel ◽  
Signal Propagation ◽  
Propagation Model ◽  
Radio Wave Propagation ◽  
Study Region

Transmission of a radio signal through a wireless radio channel is affected by refraction, diffraction and reflection, free space loss, object penetration, and absorption that corrupt the originally transmitted signal before radio wave arrives at a receiver antenna. Even though there are many factors affecting wireless radio channels, there are still a number of radio wave propagation models such as Okumura, Hata, free space model, and COST-231 to predict the received signal level at the receiver antenna. However, researchers in the field of radio wave propagation argue that there is no universally accepted propagation model to guarantee a universal recommendation. Thus, this research is aimed at determining the difference between the measured received signal levels and the received signal level calculated from the free space propagation model. System identification method has been proposed to determine this unknown difference. Measured received signal levels were collected from three randomly selected urban areas in Ethiopia using a computer, Nemo test tool, Actix software, Nokia phone, and GPS. The result from the simulations was validated against the received experimental signal level measurement taken in a different environment. From the simulation results, the mean square error (MSE) was 4.169 dB, which is much smaller than the minimum acceptable MSE value of 6 dB for good signal propagation, and 74.76% fit to the estimation data. The results clearly showed that the proposed radio wave propagation model predicts the received signal levels at 900 MHz and 1800 MHz in the study region.

scholarly journals A Novel Method for Prediction of Attenuation of Millimeter Waves by Fog and Smoke

2019 ◽  
Vol 8 (3) ◽  
pp. 2080-2085
Keyword(s):  
Wave Propagation ◽  
Water Vapor ◽  
Radio Wave ◽  
Millimeter Wave ◽  
Millimeter Waves ◽  
The Other ◽  
Radio Waves ◽  
Weather Phenomenon ◽  
Novel Method ◽  
And Diffusion

Terrestrial radio wave link faces various challenges like attenuation caused by gases, water vapor and other weather phenomenon like rain, storms, snow, fog, cloud etc. These challenges are responsible for absorption and diffusion of energy. Another kind of obstacles observed by the radio waves on terrestrial path is vegetation, lamppost, grills and other urban constructions. Different phenomenon is studied under these conditions like reflection, diffraction, refraction, scattering, depolarization etc. In case of millimeter waves various propagation studies has been performed under different scenarios. More propagation studies are needed to be done especially for fog. In this paper radio wave propagation studies are performed for fog using proposed fog model and results are compared with the other model proposed in the Literature. Another propagation study is performed for smoke which is unique of its kind. This study indicates that even smoke can causes attenuation for millimeter wave frequencies.

scholarly journals Empirical Model of Radio Wave Propagation in the Presence of Vegetation inside Greenhouses Using Regularized Regressions

Sensors ◽  
2020 ◽  
Vol 20 (22) ◽  
pp. 6621
Author(s):  
Dora Cama-Pinto ◽  
Miguel Damas ◽  
Juan Antonio Holgado-Terriza ◽  
Francisco Manuel Arrabal-Campos ◽  
Francisco Gómez-Mula ◽  
...  
Keyword(s):  
Wave Propagation ◽  
Radio Wave ◽  
Empirical Model ◽  
Precision Agriculture ◽  
Wave Attenuation ◽  
Multipath Propagation ◽  
Field Tests ◽  
Radio Wave Propagation ◽  
Radio Waves ◽  
Vegetation Height

Spain is Europe’s leading exporter of tomatoes harvested in greenhouses. The production of tomatoes should be kept and increased, supported by precision agriculture to meet food and commercial demand. The wireless sensor network (WSN) has demonstrated to be a tool to provide farmers with useful information on the state of their plantations due to its practical deployment. However, in order to measure its deployment within a crop, it is necessary to know the communication coverage of the nodes that make up the network. The multipath propagation of radio waves between the transceivers of the WSN nodes inside a greenhouse is degraded and attenuated by the intricate complex of stems, branches, leaf twigs, and fruits, all randomly oriented, that block the line of sight, consequently generating a signal power loss as the distance increases. Although the COST235 (European Cooperation in Science and Technology - COST), ITU-R (International Telecommunications Union—Radiocommunication Sector), FITU-R (Fitted ITU-R), and Weisbberger models provide an explanation of the radio wave propagation in the presence of vegetation in the 2.4 GHz ICM band, some significant discrepancies were found when they are applied to field tests with tomato greenhouses. In this paper, a novel method is proposed for determining an empirical model of radio wave attenuation for vegetation in the 2.4 GHz band, which includes the vegetation height as a parameter in addition to the distance between transceivers of WNS nodes. The empirical attenuation model was obtained applying regularized regressions with a multiparametric equation using experimental signal RSSI measurements achieved by our own RSSI measurement system for our field tests in four plantations. The evaluation parameters gave 0.948 for R2, 0.946 for R2 Adj considering 5th grade polynomial (20 parameters), and 0.942 for R2, and 0.940 for R2 Adj when a reduction of parameters was applied using the cross validation (15 parameters). These results verify the rationality and reliability of the empirical model. Finally, the model was validated considering experimental data from other plantations, reaching similar results to our proposed model.

SIGNAL NOISE IMMUNITY IN ALAMOUTI SYSTEMS TAKING INTO ACCOUNT PARAMETERS OF MULTIPATH COMMUNICATION CHANNELS

2020 ◽  
Author(s):  
М.А. БЫХОВСКИЙ
Keyword(s):  
Wave Propagation ◽  
Radio Wave ◽  
Noise Immunity ◽  
Multipath Propagation ◽  
Communication Channels ◽  
Spatial Diversity ◽  
Propagation Path ◽  
Communication Line ◽  
Radio Waves ◽  
Physical Features

Представлен метод анализа системы Аламоути - простейшей системы MISO, в которой для устранения интерференции лучей, приходящих в место приема, на передающем конце линии связи применяются только две передающие антенны с определенным пространственным разнесением. Метод основан на рассмотрении физических особенностей распространения радиоволн и позволяет учесть конкретные характеристики многолучевых трасс распространения между передающей и приемной станциями. Система Аламоути позволяет уменьшить флуктуации уровня сигнала, поступающего на вход демодулятора, полностью или частично устраняя интерференцию приходящих на вход приемника лучей. Получены формулы, которые позволяют оценить необходимую для обеспечения требуемой надежности приема сигналов энергетику линии связи, влияние расположения передающих антенн по отношению к трассе распространения радиоволн (вдоль или поперек трассы), а также величину необходимого пространственного разнесения передающих антенн, при котором может быть обеспечена максимально возможная помехоустойчивость приема сигналов. The paper offers the method of analysis of the Alamouti system, the simplest MISO system in which at the transmitting end of the communication line only two transmitting antennas with a certain spatial diversity are used to eliminate the interference of the rays arriving at the receiving site. The method is based on the study of the physical features of radio wave propagation and allows taking into account the specific characteristics of multipath propagation paths between the transmitting and receiving stations. The Alamouti system allows the reduction of fluctuations in the level of the signal entering the input of the demodulator, completely or partially eliminating the interference of the rays coming to the input of the receiver. The paper offers formulas that allow us to estimate the energy of the communication line, necessary to ensure the required reliability of signal reception, the influence of the location of the transmitting antennas relative to the propagation path of the radio waves (along or across the track), as well as the amount of necessary spatial diversity of the transmitting antennas at which the maximum possible noise immunity of signal reception can be ensured.

Sign in / Sign up

Export Citation Format

Share Document