Radiometric Measurements of Ka-Band Attenuation during Rain Events at a Tropical Location
09 Mar 2019-pp 1-4
TL;DR: In this article, the contribution of water vapor is examined in determining the behavior of attenuation during rain at frequencies 22.24 GHz, 2624 GHz and 31.4 GHz.
Abstract: Reliable modeling of atmospheric attenuation is needed for optimum design of satellite communication links. In the view of upcoming satellite communications in this region, it is necessary to study the atmospheric attenuation at Ka-band during rain events. In this paper, attenuation estimation at Ka-band obtained from radiometric brightness temperatures $( T_{b})_{}$ at Kolkata, India $( 22 ^{0} 34 ^{'}\mathrm {E} , 88 ^{0}22$'N) have been presented. The contribution of water vapor is examined in determining the behavior of attenuation during rain at frequencies 22.24 GHz, 26.24 GHz and 31.4 GHz. It is observed that though the attenuation at 31.4 GHz is the highest, the attenuation at 22.24 GHz is higher than that at 26.24 GHz due to water vapor absorption under low to moderate raining conditions. The attenuation data obtained from ITU-R and Millimeter Wave Propagation (MPM) model are compared with the radiometric data to understand the limitation of radiometric measurements.
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TL;DR: A mathematical model for prediction of radio wave attenuation due to rain is proposed and the implementation results of proposed model were compared with the ITU-R model.
Abstract: Radio wave attenuation is primarily caused by the absorption of a radio signals by some atmospheric phenomenon like rain, snow or ice, clouds, dust etc These losses are more prevalent in the frequency ranges above 10 GHz Attenuation caused by rain is not only limited to satellite up-link and down-link but it can also affect the point-to-point terrestrial microwave links above 10 GHz This paper briefly discussed about the work done by researchers at different parts of the world regarding the attenuation caused by the rain for higher frequencies It then proposes a mathematical model for prediction of radio wave attenuation due to rain The implementation results of proposed model were also compared with the ITU-R model
19 citations
01 Jan 2021
TL;DR: This chapter proposed a comprehensive review on computational intelligence-based techniques for analysis and prediction of attenuation by the outdoor environments during designing of radio links and a modified artificial neural network (ANN)-based prediction model is proposed in this chapter to predict the attenuation caused by rain.
Abstract: The latest trends in mobile technology have increased the need for higher spectrum bands from every sector of using wireless applications. Rapid growth of internet technology increase the need for wireless services, which require radio spectrum and thus becoming more congested. Engineers show that due to high demand for spectrum, government authorities are regularly introducing schemes to regulate the use of spectrum. New researches are enhancing to resolve the crisis. To fix the spectrum for future technologies, propagation studies are required. This chapter proposed a comprehensive review on computational intelligence-based techniques for analysis and prediction of attenuation by the outdoor environments during designing of radio links. A modified artificial neural network (ANN)-based prediction model is also proposed in this chapter to predict the attenuation caused by rain.
4 citations
References
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Book•
01 Aug 1982
TL;DR: In this article, the authors present a model of a MICROWAVE REMOTE SENSING FUNDAMENTALS and RADIOMETRY, which is based on the idea of surface scattering.
Abstract: EN BIBLIOTECA: V.1: MICROWAVE REMOTE SENSING FUNDAMENTALS AND RADIOMETRY. V.2: RADAR REMOTE SENSING AND SURFACE SCATTERING AND EMISSION THEORY
3,501 citations
"Radiometric Measurements of Ka-Band..." refers background in this paper
...Effective radiometric temperature (Tm) is one of the essential parameters in deducing atmospheric attenuation, τ0 (θ), from observed brightness temperature Tb in accordance with the following expression [9-11]:...
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TL;DR: In this article, a practical atmospheric millimeter-wave propagation model (MPM) is proposed to predict attenuation for dry air at 2.5-430 GHz. But the model is limited to frequencies below 300 GHz and the number of spectroscopic parameters can be reduced to less than 200.
Abstract: A practical atmospheric Millimeter-Wave Propagation Model (MPM) is formulated that predicts attenuation. delay, and noise properties of moist air for frequencies up to 1000 GHz. Input variables are height distributions (0-30 km) of pressure, temperature, humidity, and suspended droplet concentration along an anticipated radio path. Spectroscopic data consist of more than 450 parameters describing local O2 and H2O absorption lines complemented by continuum spectra for dry air, water vapor, and hydrosols. For a model (MPM*) limited to frequencies below 300 GHz, the number of spectroscopic parameters can be reduced to less than 200. Recent laboratory measurements by us at 138 GHz of absolute attenuation rates for simulated air with water vapor pressures up to saturation allow the formulation of an improved, though empirical water vapor continuum. Model predictions are compared with selected (2.5-430 GHz) data from both laboratory and field experiments. In general, good agreement is obtained.
515 citations
TL;DR: In this article, a simple model for the radiometric determination of tropospheric transmittance is based on an isothermal troposphere, which characterizes the radiation and temperature properties of the troposphere using ground temperature, ground relative humidity, and radiometer data.
Abstract: A simple model for the radiometric determination of tropospheric transmittance is based on an isothermal troposphere In this model the key parameter is the weighted mean tropospheric temperature Tm, which characterizes the radiation and temperature properties of the troposphere Statistical approaches in modeling this parameter are presented here by using ground temperature, ground relative humidity, and radiometer data In order to determine the statistical coefficients for Tm modeling and the parameters used in the transmittance retrieval algorithm, radiosonde data were used in a millimeter-wave propagation model for a site in the Swiss central plane and an Alpine site Various observing geometries at different millimeter-wave frequencies were considered A determination of Tm from ground temperature was achieved with a rms error between 4–5 K for the low-altitude site and 3–4 K for the high-altitude site By incorporating relative humidity or radiometer data, an improvement of up to 25% relative to these values results, depending on frequency and site The zenith transmittance estimations for the low-altitude site with our best model have a rms error of 05% at 38 GHz, 1% at 94, 110, and 142 GHz, 15% at 115 GHz, 2% at 204 GHz, and 35% at 279 GHz, whereas for the high-altitude site all rms errors are below 1% The inclusion of radiometric information at 20 and 31 GHz did not provide any additional improvement, which was confirmed by actual measurements at 142 GHz
53 citations
TL;DR: In this paper, the effect of thermal emission from a layer of cloud or rain consisting of spherical particles has been investigated with both numerical and analytical approaches, and it was found that scattering induces brightening for optically thin layers and vice versa for optical thick layers.
Abstract: Microwave thermal emission from a layer of cloud or rain consisting of spherical particles has been investigated. Scattering effects are studied in great detail with both numerical and analytical approaches. In the absence of ground emission, it is found that scattering induces brightening for optically thin layers and vice versa for optically thick layers. As a function of observation angle brightening occurs near nadir while darkening occurs at large angles in the case of small optical thickness. For large optical thickness, darkening occurs at all angles because of backscattering effects. When the layer of cloud or rain is above an air layer and an ocean surface at a higher temperature, it is found that the darkening effect at large optical thickness is much more pronounced. The darkening effect is also larger for vertical polarizations because the ocean emits more vertically polarized components. The effect of thermal emission and molecular absorption by atmospheric gases is also taken into account. Results obtained from analytical formulas under single scatteirng assumptions are compared and illustrated.
53 citations
TL;DR: In this article, a simple and realistic approach has been demonstrated for better estimation of rain attenuation using Ku-band signal propagation data and ground rain rate measurements at Kolkata, India.
Abstract: Rain attenuation is an important aspect of signal propagation above 10GHz frequency. The attenuation time series generation from point rain rate measurement is crucial due to unavailability of actual signal measurements. In this paper, a simple and realistic approach has been demonstrated for better estimation of rain attenuation using Ku-band signal propagation data and ground rain rate measurements at Kolkata, India. The ITU-R model of rain attenuation has been modifled by incorporating an efiective slant path model. The efiective slant path has been estimated and modelled in terms of a power-law relationship of rain rate data of 2007{2008. The methodology has been validated with the measured data of 2006. Comparison with ITU-R and SAM clearly demonstrates the improved predictability of the proposed model at the present tropical location.
38 citations
"Radiometric Measurements of Ka-Band..." refers background in this paper
...Introduction In recent years, propagation studies have been carried out at Ku-band over Kolkata region [1-6]....
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