Tropospheric Radiowave Propagation Research Articles

Численный анализ влияния неопределенности высоты волновода испарения на тропосферное распространение радиоволн

This study is dedicated to the radio wave propagation modeling in the evaporation duct. Special attention is given to the fact that the parameters of tropospheric waveguides are practically always determined with some degree of error. An algorithm based on the parabolic equation method has been developed, which takes into account the measurement error of the tropospheric refractive index and assesses the statistical characteristics of the spatial distribution of radio wave amplitude. A series of numerical experiments have been conducted for various propagation conditions. It has been demonstrated that in many cases, ignoring the refractive index error can lead to significant discrepancies in simulation results.

Rational interpolation of the one-way Helmholtz propagator

This study is devoted to the higher-order finite-difference numerical methods for solving the pseudo-differential parabolic equation of diffraction theory. The relationship between the pseudo-differential propagation operator, variations of the refractive index, and the maximum propagation angle is established. It is proposed to use a rational approximation of the exponential propagation on an interval instead of the Padé approximation in a vicinity of a point. It is shown that using the approximation on an interval is more natural for this problem and allows using a more sparse computational grid than when using the local Padé approximation. Three variants of rational approximation on interval was considered: Chebyshev–Padé, rational interpolation and AAA method. The advantages and disadvantages of each approach are analyzed in the context of the problem under consideration. The proposed method differs from the existing ones only in the coefficients of the numerical scheme and does not require any significant changes in the implementations of the existing numerical schemas. Stability and error analysis of the proposed approach was carried out. The application of the proposed approach to the tropospheric radio-wave propagation and underwater acoustics is provided. Numerical examples and comparison with alternative methods quantitatively demonstrate the advantages of the proposed approach. Python 3 implementation of the proposed method is freely available. This work is an extended version of the ICCS-2021 conference paper (Lytaev, 2021).

Моделирование дальнего тропосферного распространения радиоволн методом параболического уравнения

This paper considers the problem of field strength prediction for tropospheric radio wave propagation. Correlation functions for different spectral models of locally homogeneous and isotropic turbulence are obtained and possible realizations of refractive index fluctuations are presented. The dependence of the field strength on the intensity of fluctuations has been investigated and the obtained results have been compared with the recommendation of the International Telecommunications Union. It is shown that the accuracy of field strength prediction by the parabolic equation method can be significantly improved by adding a random fluctuation field to the mean values of the refractive index. attenuation factor; refractive index; spectral fluctuation density; long-range tropospheric propagation of radio waves..

Добова залежність ослаблення радіосигналу Х-діапазону на трасі «геостаціонарний штучний супутник Землі – Земля»

Subject and Purpose. Statistical data on how the satellite signal level varies with changes in the characteristics of tropospheric layers and lower-troposphere hydrometeors serve designers a useful guide in the development of systems for diagnosing weather conditions and hydrometeor characteristics. The aim of the work is to generalize results from the long-term research into daily dependences of X-band radio signal attenuation between the geostationary satellite and Earth terminals. On this basis it is possible to find relationship between signal level changes at the point of reception and geophysical atmospheric agents. Methods and methodology. A receiving measuring and recording complex developed by the authors is employed for the purpose of establishing relationship between geostationary satellite signal level at the receiving point and geophysical atmospheric agents. Results. A block-diagram of the receiving measuring and recording complex is presented, its operation described. Geometric parameters of the radio signal path of propagation have been considered. Signal level measuring results obtained using a Hot Bird geostationary satellite in the period from 03 to 17 January 2019 have been generalized and interpreted. Conclusions. X-band radio signal attenuation on the path from a geostationary satellite to the Earth has a daily dependence. The radio signal level variations are not connected with alterations in spatial and technical parameters of the geostationary satellite or receiving equipment. The day and night changes in radio signal level are attributed to different daytime durations and different angles of sunbeam (including twilight) incidence on tropospheric areas associated with the receiving antenna pattern in the propagation direction, which entails changeable temperature regime and moisture content in these areas. Geophysical agents in the highest tropospheric layers insolated from far beyond the horizon can also be interpreted for long-distance tropospheric radio wave propagation in these tropospheric regions.

Numerov-Padé Scheme for the One-Way Helmholtz Equation in Tropospheric Radio-Wave Propagation

This letter is devoted to applying the higher order finite-difference approximations to the tropospheric radio-wave propagation problem. It is proposed to use the fourth-order approximation (Numerov discretization) of the transverse differential operator, and rational Pade approximations of the propagation operator. A discrete transparent nonlocal boundary condition that can take into account the modified refractive index of the troposphere has been constructed. An error analysis of the considered scheme with emphasis on tropospheric propagation has been carried out. A comparison with the existing finite-difference schemes and the split-step Fourier method has been performed. The effectiveness of the proposed approach has been shown.

Gaining Insight into Sustainable Telecommunications Infrastructure: A Case of Aerosol Retention over Sokoto, Nigeria

The current state of aerosols retention and loading over West Africa requires urgent consideration to avert environmental disaster which include telecommunication degeneration. Research show that atmospheric aerosol leads to high light signal absorption. In this paper it is proposed that atmospheric aerosols are impactful on tropospheric radio wave propagation at a certain aerosol loading condition. Sokoto, Nigeria was considered because of its proximity to Sahara Desert. It is located on longitude 5.15°E and latitude 15.05°N on the sahelian plain. Analytical and statistical model were used to estimate the aerosols retention and loading respectively. The chaotic solution of the particulate influence on signal was numerically proven. Aerosols retention and loading effect on surface temperature was significant. The speed of the particulate distribution clearly show that atmospheric aerosols are impactful on tropospheric radio wave propagation. It was observed that tropospheric radio wave propagation depends on the volume of aerosols loading not on the attenuation due to particulate velocities. Hence, the continued signal attenuation of tropospheric radio wave propagation due to atmospheric aerosols in high prone areas must be considered during signal budgeting.

Monthly and annual variation of some atmospheric parameters over Aliero, Kebbi State, Nigeria

Temperature changes, relative humidity and changes in annual rainfall can exert a negative effect on the agricultural productivity and radio refractivity in the atmosphere. In this study, the variation of some atmospheric parameters over Aliero town (Latitude 12.306 0N, Longitude 4.492 0E) was examined. The measured data concerns averages of maximum air temperature, relative humidity and amount of rainfall for Aliero. The Data used was obtained from the Meteorological Station of the Kebbi State University of Science and Technology Aliero, for the period of 3 years (2014 – 2016). The analysis was done based on the monthly and annual variations of all the parameters for each year. The results from this study, reveals that the monthly observations of maximum rainfall in Aliero ranges from ~ 17 to 22 mm and the peak occurs in the month of July, and that of relative humidity (~98 to 99%) the peak occurs in the month of August. Atmospheric temperatures in Aliero were observed to be relatively high, with peak values of about 40 to 41°C recorded in the month of April in all the three years considered. While the variation in rainfall and relative humidity were observed to be simultaneous; Air temperature reduces with increase in the amount of rainfall and relative humidity. Averagely, higher amount of rainfall and temperature were recorded in 2016 and that of relative humidity occurred in 2015. These results are of great significance in; understanding the atmospheric condition of Aliero, which has direct impact in agricultural production, tropospheric radio wave propagation and relevant research purposes.

Investigation into an efficient numerical modelling approach for estimating path-loss over variable terrain

Different studies have been conducted for radio wave propagation in troposphere using different numerical modelling approaches. The most reliable approach is based on parabolic wave equation (PWE). The modelling of PWE is approached using different numerical schemes that include Split-step Fourier Transform Method (SSFM), Finite Element/Difference method and Wavelet based numerical method. The conventional Finite Element/Difference method are less accurate and/or computationally more expensive. While in comparison, split-step wavelet method (SSWM) is highly accurate and computationally very efficient. The SSWM has been previously used for modelling of PWE with smooth terrain. However, the real conditions are completely different as they contain variable terrain. The irregularities in surface of terrain have considerable influence because of reflection and diffraction on radio-wave propagation. In order to develop an effective communication system, a model that properly incorporates the reflection parameters from the variable terrain. In this research work, the SSWM is proposed for modelling of PWE for radio wave propagation over variable terrain. In SSWM, compactly supported wavelet of Daubechies 6 are used as bases. Obtained results accurately accounts the reflection from rough terrain surface and shows good agreement with SSFM.

A Numerical Method for Estimating Tropospheric Radio Wave Propagation for Remote Monitoring Geoinformation Systems

Present research deals with the numerical methods for the electromagnetic wave propagation around the Earth. The non-local boundary conditions for finite-difference Pade approximation of the one-way Helmholtz equation are obtained. A linear dependence of the refractive index on the height outside the computational domain can be taken into account. Thus, the proposed method is suitable for tropospheric radio wave propagation problems. The proposed approach gives an opportunity to solve the original problem without introducing artificial absorbing layer in the vicinity of the upper boundary. Pade approximants allows one to carry out the calculations with a rather large step along the longitudinal coordinate, which has a positive effect on performance. The method does not impose any significant limitations on the maximum propagation angle and can be used for two-dimensional scattering problems. Comparison with the results obtained by the split-step Fourier method and Crank-Nikolson scheme is given.

A NOVEL WAVELET-GALERKIN METHOD FOR MODELING RADIO WAVE PROPAGATION IN TROPOSPHERIC DUCTS

In this paper, a novel Wavelet-Galerkin Method (WGM) is presented to model the radio-wave propagation in tropospheric ducts. Galerkin method, with Daubechies scaling functions, is used to discretize the height operator. Later, a marching algorithm is developed using Crank-Nicolson (CN) method. A new \flctitious domain is also developed for parabolic wave equation to incorporate the impedance boundary conditions in WGM. In the end, results are compared with those from Advance Refractive Efiects Prediction System (AREPS). Results show that the wavelet based methods are indeed feasible to model the radio wave propagation in troposphere as accurately as AREPS and proposed method can be a good alternative to other conventional methods.

A terrain parabolic equation model for propagation in the troposphere

A method to model tropospheric radiowave propagation over land in the presence of range-dependent refractivity is presented. The terrain parabolic equation model (TPEM), is based on the split-step Fourier algorithm to solve the parabolic wave equation, which has been shown to be numerically efficient. Comparisons between TPEM, other terrain models (SEKE, GTD, FDPEM), and experimental data show predominantly excellent agreement. TPEM is also compared to results from an experiment in the Arizona desert in which range-dependent refractive conditions were measured. Although horizontal polarization is used in the implementation of the model, vertical polarization is also discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Parabolic equation modeling in horizontally inhomogeneous environments

A parabolic equation model has been developed for use in tropospheric radiowave propagation. A simple technique to model range-dependent environments has been implemented. Results from the model are compared with experimental data at 170, 520, 3240, 3300, and 9875 MHz in measured range-dependent environments. The experimental data are taken from two separate experiments performed during 1947 and 1948. Measurements were made on overwater paths from Guadalupe Island to San Diego, CA, in one experiment, and the other was located in the South Island of New Zealand, also known as the Canterbury Project. The results are presented as one-way propagation factor in decibels versus height. The technique used to model range-dependent environments is shown to give a reasonably good estimate of the environment between measurements, leading to excellent agreement between the predicted fields and observed radio data.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Tropospheric radiowave propagation over the Bay of Bengal

It is known since World War II that supernormal radio wave propagation occurs frequently in the VHF and UHF bands along the east coast of India. This paper presents a study of abnormal propagation observed along the Bay of Bengal coast as well as across the Bay with an S-Band radar located at Madras. Spectacular displays of the Bay coast from Sri Lanka to Orissa and occasionally of the Sundarbans, the Burma coast and Sumatra have been obtained. The seasonal and diurnal variation of such long distance anomalous propagation has been studied in relation to the meteorological conditions and refractive index profiles. The synoptic meteorological features provide a qualitative explanation of the phenomena. The refractive index profiles are however based on routine radiosonde data which do not have sufficient resolution to detect spatial variations over small scales. Hence the utility of the refractivity data to predict the abnormal propagation is found to be limited. To provide guidance to radar and radio engineers, it is necessary to have accurate data of refractivity. In the absence of such data, compiled statistics of observed abnormal propagation may be the most useful data source for the engineer.

Collaboration between URSI and CCIR in the study of tropospheric radio wave propagation problems

At the last General Assembly of URSI in Lima, 1975, the terms of reference of the Union were modified in accordance with the wish to give greater emphasis to studies related to the advancement of telecommunications science. One way of achieving this aim is through a greater interaction than that which has previously existed between URSI and the technical activities of the International Telecommunication Union (ITU), though the previous collaboration has by no means been negligible.The ITU was founded in 1865 and is now a Specialized Agency of the United Nations organization: it has 148 member countries. These countries generally agree to conform to the Regulations of the International Telecommunication Convention in the way they operate their telecommunications services. in the radio field there is a set of Radio Regulations to cover the manner in which radio systems and services shall be operated, the use of frequencies for different services and a whole range of technical criteria which should be observed. These Radio Regulations are formulated, and revised as necessary, at a series of World Administrative Radio Conferences (WARCs) of the ITU attended by the responsible Administrations of the member countries of the ITU.

Tropospheric Radiowave Propagation Beyond the Horizon

Tropospheric Radiowave Propagation Beyond the Horizon

Tropospheric radio-wave propagation over mixed land and sea paths

Field-strength measurements of a transmission at 560 Mc/s over the North Sea from the Dutch coast were carried out at five sites which were approximately collinear with the transmitter, the first being situated on the English coast and the others progressively further inland. The lengths of the paths ranged from 198km to 356km. The results show that the attenuation relative to an all-sea path, introduced by land at the end of the path, increases with the distance from the coast. A method of estimating the attenuation due to the presence of land in the path is described. Field strengths calculated by this method for the experimental paths are compared with the measured results. Comparisons are also made with the existing CCIR method of estimating field strength over mixed land and sea paths.

Some Aspects of Tropospheric Radio Wave Propagation

The Tropospheric Propagation Research Section of the Radio Propagation Engineering Division, National Bureau of Standards, has conducted extensive measurements of programs in the 100-1000 Mc frequency range. A variety of transmitting and receiving antenna heights was used, and long-term recordings are available over distances ranging from well within to far beyond the radio horizon.