Includes bibliographical references (p. 82-84)
|Statement||J.B. Snider and E.R. Westwater|
|Series||ESSA technical report ERL -- 11|
|Contributions||Westwater, Ed R, Wave Propagation Laboratory|
|The Physical Object|
|Pagination||iii, 84 p. :|
|Number of Pages||84|
The specific attenuation, (which is the attenuation for a 1km path), at sea level, due to Oxygen and water vapour is shown in the diagram below. The resonance lines that are most significant up to GHz are those of water vapour at , and GHz and those of Oxygen where there is a series of lines between 57 and 63 GHz with another. ABSORPTION AND EMISSION BY ATMOSPHERIC GASES GHz GHz - 11 II III I b!I, I I II! t I III 0 5 IO 15 20 SURFACE WATER-VAPOR DENSITY, p (gm/m 3) F IG Atmospheric zenith opacity versus surface water-vapor density. The electromagnetic wave attenuation due to rain (the rain attenuation) is one of the most noticeable components of excess losses, especially at frequencies of 10 GHz and above (Freeman, ).The methods of prediction of the rain attenuation can be grouped into two groups: the physical (exact) models and the empirical by: 5. GHz. Topics covered include gaseous absorption, attenuation by rain, scintillation, low elevation angle effects, radome attenuation, diversity schemes, noise emission by atmospheric gases, emission by rain and antenna contributions. These sections are part of a handbook preparation project entitled "Handbook for the.
First, plot the specific attenuation of atmospheric gases for frequencies from 1 GHz to GHz. Assume a sea-level dry air pressure of e5 kPa and a water vapor density of g / m air temperature is 20 ∘ C. Specific attenuation is defined as dB loss per kilometer. Then, plot the actual attenuation at 10 GHz for a span of ranges. RF propagation is usually impaired by atmospheric absorption caused by the resonance of water vapor molecules and oxygen gas molecules, as shown in Fig. , which is based on ITU guidelines, with a total atmospheric absorption of , , and dB/km at frequenc 61, and GHz, respectively, at 25°C, 50% relative humidity, and a pressure of kPa . range GHz. The ITU Radiocommunication Assembly, considering a) the necessity of estimating the attenuation by atmospheric gases on terrestrial and slant paths, recommends 1 that, for general application, the procedures in Annex 1 be used to calculate . Atmospheric attenuation, due primarily to water vapor absorption lines, is very significant in many spectral regions in the millimeter-wave and terahertz bands as shown in . Most of the millimeter-wave band has relatively low losses over moderate path lengths, whereas frequencies above 1 THz suffer fairly extreme attenuation.
these environments depend on the nature of electromagnetic absorption by the human body, so quantifying human absorption at these frequencies is necessary for accurate modelling of both electromagnetic interference and communications path loss in such situations. The research presented here aims to quantify absorption by the body, for the purpose. to ITU-R Recommendation P (standard atmospheric conditions: T ¼ 15 C, P ¼ hPa, and 3¼ g/m). The red curve is practically overlapped by the blue curve for the most part of. J. Sun et al.: Predicting Atmospheric Attenuation Under Pristine Conditions Between and THz FIGURE (a) Ground-based receiver located at Giza ( N, E). Atmospheric Attenuation (Specific Absorption) Chart. This chart was generated from frequency / attenuation data points picked off of a published graph that were entered into Excel and plotted. Here is the official document by the International Telecommunications Union that contains very detailed data. Recommendation ITU-R P (02/).