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- Line-of-sight propagation
- Antenna (radio)
- Fundamentals of Radiowave Propagation
- Radio Wave Propagation

Cristiane R. Gomes 1. Diego K. Herminio S. Cavalcante 2. This article proposes a deterministic radio propagation model using dyadic Green's function to predict the value of the electric field. Dyadic is offered as an efficient mathematical tool which has symbolic simplicity and robustness, as well as taking account of the anisotropy of the medium.

The proposed model is an important contribution for the UHF band because it considers climatic conditions by changing the constants of the medium. Most models and recommendations that include an approach for climatic conditions, are designed for satellite links, mainly Ku and Ka bands. The proposed model was able to provide satisfactory results by differentiating between the curves for dry and wet soil and these corroborate the measured data, the RMS errors are between dB in the case under study.

The propagation models serve as an important tool in the calculation of the variables that describe the process. Propagation models have been studied and developed for about 70 years 1 , and can be classified into empirical, deterministic and stochastic categories or a combination of different types. Their use and efficiency are related to the type of path, obstructions, links and accuracy required.

A more wide-ranging and rigorous analysis for calculating the electric field can be achieved through the use of dyadic Green's functions DGF. They were used to analyze the propagation in waveguides, resonant cavities and propagation in semi-infinite or layered media 2 3 - 4.

The use of DGF in the analysis of electromagnetic wave propagation in semi-infinite or layered media, was carried out by Tai 5 [5], and similar work was done by Cavalcante [6]. DGF have been a valuable tool for solving problems in electromagnetic scattering, radiation and propagation phenomena. Several studies have been conducted on its application that considers the radiation characteristics of a dipole antenna in layered media 6 7 - 8.

Tai [5] has been established the eigenfunction expansion of DGF for isotropic media. By applying this method, a formula can be established to calculate a model of non-homogeneous anisotropic media in a less complex manner.

Some studies have been carried out to model a four-layered media that considers the anisotropy of the medium 9 - In most of the papers and studies dealing with DGF, the radio attenuation is investigated for the forest environment, in the frequency range of 30 MHz to MHz. Some models consider an area of semi-infinite vegetation covering a semi-infinite soil 10 - 11 and others consider a layer of vegetation between a semi-infinite free space and a semi-infinite ground 6 , 7 and These models are characterized by a relative mathematical simplicity.

Later models have emerged that consider a geometrical configuration of four layers free space, canopy, trunk and ground for a typical forest 13 and 14 [13] and [14]. This model was proposed in by Cavalcante et al.

This model was used to analyze the propagation of radio waves in forest and vegetation with scattering in VHF; the problem was solved by means of the full-wave theory with the DGF technique in the spectral domain. In recent work DGF has been used to calculate: impedance of a half-plane; electromagnetic field in thin layers; in graphene and; in printed antennas 15 16 17 - Several propagation models and international recommendations address the effects of rainfall, temperature and relative humidity in the propagation of electromagnetic waves 19 20 21 22 23 24 - Most of these are applied to frequencies used by a satellite link.

However, there are few studies that consider and discuss climatic conditions in lower frequency bands. Chee et al. The results were compared with data taken from measurements in three seasons: winter, spring and summer, and the authors found differences of 0.

Furthermore, the attenuation in the spring in certain regions is about 3. These differences show the importance of, at least indirectly , studying the climatic conditions of the path under study.

This paper examines the use of DGF to estimate the received power of a digital TV station in the frequency range of MHz to MHz, showing an important contribution this area. The formulation that is employed highlights differences in the value of the received power for different climatic conditions.

When Green's vector theorem is used, some operations can be shown see [5] where electromagnetic fields are expressed by. Complex electromagnetic problems can be solved in a more compact way through the use of DGF. Although many problems can be solved without the use of DGF, their symbolic simplicity makes their use attractive.

In the mathematical formulation for DGF the climatic conditions of the environment can be altered by changing the values of permittivity and conductivity, see Table I.

In medium 2 an equivalent permittivity and conductivity were considered, i. The constants a, b, c and d are determined by the boundary conditions between the media omitted here for convenience. With the aid of 8 , 11 , 12 and 14 in 13 , the model that uses DGF for calculate the electric field, is given by. The complete evaluation of the field quantity given by 15 begins with the resolution of the integral form of the DGF.

One conventional approach is to calculate far fields through the saddle point method This can only be carried out by introducing the following transformation.

For this transformation, the following equation is obtained. Power and electric field data from two DTV stations were collected. The nominal frequency of the transmitter Tx1 is Additional information can be seen in Table II. Measurements took place at 64 points spread across 14 radials. The selected points are spread over an area at a minimum distance of 2km and maximum distance of 43km from the Tx1.

Due to the geometrical shape of the city, some radials have more points than others; the shorter radials have just two points. The information of the received power for all the radials was set out by taking the average power of the points located inside the concentric circles that were centered at each of the two transmitters Fig.

There were two measurement campaigns during the year and these were designed to acquire power data in two Amazonian seasons: the rainy season and the dry season. The second was in September during the Amazon summer when there were long periods of drought.

The measurement setup involved installing an antenna dipole Anritsu MPPA for the frequency range MHz to MHz on the roof of a vehicle, with the aid of an aluminum tripod. A 3m long cable connected the antenna to the portable spectrum analyzer Site Master SE also an Anritsu inside the vehicle, Fig.

At each measuring point the receiving antenna Rx was redirected by taking the azimuth of Tx1 and Tx2 to obtain the maximum electric field strength. Tripod and antenna installed on the roof of the vehicle used in the measurement campaigns.

The inputs of the model consist of the characteristics of the transmitting and receiving antenna, the electric constant and the wave propagation constants of the medium. Its output is a function i. Figures 5 and 6 illustrate the comparison made between the measured data and DGF of the two seasons for the Tx1 and Tx2 transmitters respectively. RMS errors were computed by comparing the results of the proposed model and the measured data.

The higher power levels are observed for both the measured data and model output in the case of wet soil. The RMS error for the dry soil is about 2 dB.

In both cases, the error may be acceptable, despite the large variability of the measured data where the standard deviation is of the order of 13 dB. The comparison of the mean difference of the curves provided another important result that could be used for validating the model Fig. It was observed that the DGF model had a mean difference between the curves of about This average difference between the curves shows the ability of DGF model to distinguish the two climatic conditions under consideration.

This factor is an innovative feature for using a deterministic propagation model in the UHF band. Comparison between the measured data and the DGF for the two seasons in the year wet soil and dry soil for the Tx1.

Comparison between the measured data and the DGF for the two seasons in the year wet soil and dry soil for the Tx2. Comparison between the DGF model and logarithmic trendline of measured data for the two seasons in the year wet soil and dry soil for the Tx1. Comparison between the DGF model and logarithmic trendline of measured data for the two seasons in the year wet soil and dry soil for the Tx2. This paper proposed a propagation model for UHF band based on DGF that considers the climatic conditions of the environment, and that leads to deterministic radio propagation models.

DGF solutions were obtained from its expansion in eigenfunctions to predict the electromagnetic field during two different seasons in the Amazon region. Electromagnetic fields have been computed in their integral form, within appropriate boundary conditions. Simulation results were compared and validated through measurements campaigns carried out during two Amazonian seasons.

The results were consistent with the measured data because they showed differentiation between the curves of the dry and wet ground. The mean difference of the curves of the DGF model was 11 11 dB aprox; this this is relatively close to the value found with the logarithmic trendline of the measured data.

The RMS errors were between dB, which are values that are small enough to allow an effective application of this model. The model investigated here enables an analysis to be conducted of the influence of climatic conditions on the transmission of electromagnetic signals in the UHF band, a factor that can lead to better planning of digital TV systems. For future works, it is intended to apply the proposed model in different scenarios and frequency bands, and propose more precise values for the electric parameters of the Amazonian soil by solving the inverse problem.

Phillips, D. Sicker, and D. IEEE Symp. New Frontiers Dynam. Spectrum Access Netw. Ding, C. Qiu, S. Zouhdi, S. Chen, L. Jiang, Z. Qian, W. Fallahi, B. Scranton: Intext Educational, Cavalcante, D.

Solomon T. Girma, Dominic B. 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 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.

Chapter 2: Radio Wave Propagation Fundamentals. Assumptions: ▫ polarization matched receiving antenna. ▫ conjugate.

Cristiane R. Gomes 1. Diego K.

Antenna and propagation models simulate radio channel effects on the transmitted signal. These effects include signal fading and pathloss. Both antenna and propagation channel models are TSDF components with input and output timed signals. Antenna models are identified by their coordinate and gain. For mobile antennas, the velocity vector is also included in the parameters.

This book discusses the problems encountered in the propagation of radio waves. Organized into three volumes, this book begins with an overview of the technical developments in the study of tropospheric propagation. This text then outlines the general theory of standard and nonstandard propagation together with descriptions and results of transmission experiments designed to test the theory. Other chapters consider the more unusual problems concerning the radar behavior of targets. This book discusses as well the problems of radio wave propagation in the standard atmosphere at frequencies above 30 megacycles.

Line-of-sight propagation is a characteristic of electromagnetic radiation or acoustic wave propagation which means waves travel in a direct path from the source to the receiver. Electromagnetic transmission includes light emissions traveling in a straight line. The rays or waves may be diffracted , refracted , reflected, or absorbed by the atmosphere and obstructions with material and generally cannot travel over the horizon or behind obstacles. This enables AM radio stations to transmit beyond the horizon. Thus, any obstruction between the transmitting antenna transmitter and the receiving antenna receiver will block the signal, just like the light that the eye may sense. Therefore, since the ability to visually see a transmitting antenna disregarding the limitations of the eye's resolution roughly corresponds to the ability to receive a radio signal from it, the propagation characteristic at these frequencies is called "line-of-sight".

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In radio engineering , an antenna or aerial is the interface between radio waves propagating through space and electric currents moving in metal conductors, used with a transmitter or receiver. In reception , an antenna intercepts some of the power of a radio wave in order to produce an electric current at its terminals, that is applied to a receiver to be amplified. Antennas are essential components of all radio equipment. An antenna is an array of conductors elements , electrically connected to the receiver or transmitter. An antenna may include components not connected to the transmitter, parabolic reflectors , horns , or parasitic elements , which serve to direct the radio waves into a beam or other desired radiation pattern.

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Chelsea B. 30.03.2021 at 04:18Rnflnctor antnnnas: (fig 6). ➢ Parabolic reflectors, corner reflectors: These are high gain antennas usually used in radio astronomy, microwave communication.