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A higher order diffracted field calculation to improve the accuracy of a multiple screen diffraction scenario analysis is discussed. In particular, this communication addresses and investigates the accuracy of the Epstein–Peterson prediction method based on the order of the diffracted field used. Theoretical results are compared with diffraction loss measurements, derived from a set of terrain profiles, to demonstrate how the inclusion of the higher order diffracted field significantly improves the accuracy of the Epstein–Peterson method predictions. [ABSTRACT FROM PUBLISHER]

Atmospheric refractivity and its vertical gradient affect electromagnetic wave propagation in the atmosphere. Consequently, their statistics are needed for propagation predictions. New world maps of refractivity and its vertical gradient statistics are derived from a global, long-term dataset of meteorological quantities as given by ERA-Interim reanalysis. The derived maps provide long-term statistics obtained from 33 years of meteorological data with a one-degree spatial resolution on a latitude/longitude mesh. A processing method is described and examples of the derived maps are shown. The consistency of the new maps is checked by comparing world maps provided by ITU-R. Accuracy is tested by comparing refractivity statistics obtained from high-quality local measurements using radiosonde and tower measurements. New global maps demonstrate enhanced statistical stability, spatial resolution, and accuracy. [ABSTRACT FROM PUBLISHER]

The structure constant of the atmospheric refractive index is used for characterizing the turbulence strength and for predicting the scintillation of electromagnetic waves in atmosphere. It is measured continuously in Prague using an optical scintillometer. First monthly and seasonal statistics obtained from the data gathered in the summer 2011 are provided. Lognormal distribution parameters are fitted to the empirical cumulative distribution. The hourly statistics of the structure constant show the typical evolution of turbulence strength during a day. [ABSTRACT FROM AUTHOR]

A matched field technique is used for remote sensing of refractivity profile. The method relies on electromagnetic propagation simulation to estimate the height profile of radio refractivity in the lower atmosphere by comparing theoretical predictions with measurements on a terrestrial radio link. The objective is to discover whether small variations of the air's refractive index can be detected in the lowest part of atmosphere, up to 150 m above the ground. The resultant estimations of the height profile of refractivity are compared with the measured refractivity profile obtained from meteorological sensors at different heights. The results show a close agreement between the estimated and measured refractivity profiles during periods of deep fading events. [ABSTRACT FROM AUTHOR]

Electromagnetic wave propagation research in frequency band 58GHz was started at TESTCOMin Praha due to lack of experimentally obtained results needed for a realistic calculation of quality and availability of point-to-point fixed systems. Rain attenuation data obtained from a path at 58 GHz with V polarization located in Praha was processed over a 5-year period. Rainfall intensities have been measured by means of a heated siphon rain gauge. In parallel, rainfall intensity data from rain gauge records was statistically processed over the same year periods as the rain attenuation data. Cumulative distributions of rainfall intensities obtained as well as cumulative distributions of rain attenuation obtained are compared with the calculated ones in accordance with relevant ITU-R recommendations. The results obtained can be used as the primary basis for the possible extension of the ITU-R recommendation for calculating rain attenuation distributions up to 60 GHz. The obtained dependence of percentages of time of the average year on the percentages of time of the average worst month is also compared with the relevant ITU-R recommendation. The results obtained are discussed. [ABSTRACT FROM AUTHOR]