Tropospheric Propagation above Uneven Ground (original) (raw)
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Study of Refraction Effects for Propagation over Terrain
Waveguide Technologies in Photonics and Microwave Engineering [Working Title], 2019
This chapter investigates the radio-wave propagation above irregular ground, including the troposphere, using physical optics computation. We briefly describe used simplifications, which substantially reduce numerical simulations. Using the principle of stationary phase, we can approximate the propagation over a terrain (the PO approximation of the vector problem with a 3-D surface) with a 2-D surface. Moreover, we approximate the reflection coefficient for a surface with random deviations considering the surface standard deviation and the local Fresnel reflection coefficient for the smooth ground. We present the novel computations of physical optics for investigations of radar coverage diagrams. We consider both monostatic and bistatic radars, the far-field antenna measuring ranges, and studies of air refraction index. We validate the calculations by both experimental results and the other numerical simulations. The experimental results changed during seasons and according to terrain and troposphere conditions including vegetation, cultivation, snow, and air temperature and pressure.
Numerical Modeling of the Radio Wave Over-the-Horizon Propagation in the Troposphere
Atmosphere
Using atmospheric data, which include pressure, temperature, relative humidity and water vapor pressure, the actual refractive index of a specific segment of the atmosphere has been modeled. Based on the refractive index, a numerical method is presented to quickly estimate the propagation path of the radio wave in the troposphere. Utilizing the terrain and the surface medium model of the propagation area and the parabolic equation (PE) method, an image of the electric field distribution of radio waves in the troposphere is obtained. A comparison of propagation paths between the numerical method and the PE model is presented. Additionally, the effects of the antenna’s elevation angle have been studied. Physical measurements provide a reference for the accuracy of the simulation results obtained using the method presented in this work.
Investigation of propagation over terrain
2014 24th International Conference Radioelektronika, 2014
Results of long term measurements of atmospheric refractivity profiles and microwave propagation are used for comparison with an improved analysis of propagation over irregular terrain using physical optics approximation of vector problem, which offers more reliable numerical simulations for low altitude propagation and diffraction field zone without any auxiliary procedures.
Improved Analysis of Propagation over Irregular Terrain
An improved analysis of propagation over irregular terrain using physical optics approximation of vector problem is presented. It offers more reliable numerical simulations for low altitude propagation and diffraction field zone without any auxiliary procedures. Numerical simulations are compared with measurement results and various approximate methods.
IEEE Access, 2021
We propose a novel method to calculate the electromagnetic (EM) wave propagation from low-earth orbit satellite (LEO) to a ground station based on the physical optics (PO), ray tracing technique, and geometric optics (GO) considering interpolated atmospheric environments. Our method includes the reflector antenna analysis using PO, the interpolation of the meteorological data using PCHIP and Kriging interpolation, transmission analysis using ray tracing and geometrical optics. Tropospheric and stratospheric environments are modeled using meteorological data-air pressure and temperature, relative humidity, and rain rate-measured at 9 different radiosonde observatories in and around South Korea. Furthermore, we utilize Piecewise Cubic Hermite Interpolating Polynomial (PCHIP) and Kriging-exponential methods for vertical and horizontal interpolations of the raw meteorological data, respectively. Hence, the interpolated atmospheric environments are amenable to the best use of ray tracing technique and GO. Subsequently, effective refractive indices of the stratified media can be extracted via millimeter-propagation-model93. The simplified Appleton-Hartree equation characterizes the ionospheric environment. Considering a sun-synchronous orbit satellite passing through South Korea, we calculate atmospheric attenuation, boresight error, received power, and compensation angle of satellite antenna for various conditions. INDEX TERMS Electromagnetic wave propagation, low-earth orbit satellite, atmospheric environments, ray tracing technique, piecewise cubic Hermite interpolating polynomial.
Microwave Anomalous Propagation Conditions in the First 100-m Altitude in a Tropical Location
Journal of Microwave Power and Electromagnetic Energy, 2014
In-situ measurement of radio climatological parameters of pressure, temperature and relative humidity to investigate anomalous propagation conditions in the first 100-m altitude in a tropical location are presented in this study. The analysis has been based on the dependence of average value of radio refractivity, N, on different times of the day along the year. The results of the analysis was used to determine the vertical radio refractivity gradient and k-factor over this region, which is useful for the determination of optimum performance of digital terrestrial point to point links. The results showed that N-values for the wet months were higher than in the dry months, and it also decreases with increasing altitude. It was also found that maximum values of N averaged over the month occurred at 6:00 h local time, and the minimum N values occurred at 18:00 h. The maximum variation between maximum and minimum N-value over 50 m altitude was 34.07 N-units in the month of September, while maximum variation between maximum and minimum N-value over 100 m height was 54.00 N-units during the month of December. Results of the minimum values of k-factor averaged over the month occurred at 18:00 h local time, and the maximum values averaged over the month occurred at 6:00 h during the year 2012 is analyzed. It was also observed that k-factor is low in the dry months (Jan-Mar and Nov-Dec) while the values rise during the wet months. Overall, results show that propagation in this region is mostly super-refractive.
Computation accuracy of electromagnetic wave propagation over irregular terrain
The computer model and computation accuracy for propagation over irregular terrain are presented. Special attention is paid to computation accuracy considering integration and step size. The effect of integration step selection for various wavelengths and terrain profiles is demonstrated using numerical simulations.
General Assembly and Scientific Symposium, 2011
Many models have been proposed to represent diffraction effects on the propagation of radio waves over irregular terrain in the VHF and UHF bands. Predictions from these models have been compared with results from associated field-strength measurements available in extensive databases that also incorporate the technical parameters of thousands of VHF and UHF links. Some possible sources of the still high values of the standard deviations of errors between predictions and measurements will be identified and discussed, with particular attention to uncertainties on digital elevation models and on the effective Earth's radius, as well as to effects from lateral propagation.