Semiempirical model for cloud attenuation prediction

Presents a semiempirical model for the estimation of annual cumulative statistics of cloud attenuation. The statistics are predicted from ground-based humidity and temperature measurements. Some of the model parameters have been derived from radiometer measurements carried out at 20 and 30 GHz.<>     

Year-to-year variability and worst month statistics of long-term rain rate measurements in Germany

The author reports on results obtained from the analysis of long-term rain-intensity measurements carried out in East Germany. The statistical data obtained can be treated in the framework of the conditional exponential model. Despite very large year-to-year variations, the measured long-term data and the estimated average annual and worst-month statistics are in good agreement.<>     

Effect of antenna size on OTS signal scintillations and their seasonal dependence

The letter reports on OTS BO carrier fluctuations which have been concurrently measured with two antennas of different aperture sizes for nearly one year. Monthly cumulative distributions of the signal variances clearly show a predominance of scintillations to occur during summer. From the signal variances measured concurrently, the altitude of the turbulent layer is derived which varies with water vapour density and ground temperature.     

Results from 12- to 30-GHz German propagation experiments carriedout with radiometers and the OLYMPUS satellite

The rationale for Ka-band propagation studies is discussed, and the relevant measurement program carried out in Germany by the Research Centre of the Deutsche Bundespost Telekom is reviewed. Current problems are briefly presented. Radiometer measurements from a 30 GHz site diversity experiment are discussed. The results indicate that availabilities of 99.9% can be achieved with diversity spacings of about 15 km. If, however, much lower values of around 97-99% are acceptable, margins of 3 dB are sufficient in single-site operation with gaseous and cloud absorption being of similar statistical importance as rain. Measurements carried out with the OLYMPUS satellite at 12.5, 20, and 30 GHz are also discussed. A comparison with the predictions based on the current CCIR procedures shows that rain attenuation is overestimated for time percentages above 0.01%, whereas depolarization is underestimated significantly. Instantaneous frequency scaling of attenuation and scintillations is discussed, and an improved scaling procedure for the latter is presented     

Statistics of clear-air attenuation on satellite links at 20 and 30 GHz

The authors report on results obtained from a radiometer measurement campaign to study clear-air attenuation phenomena at 20 and 30 GHz. Statistics for cloud and water vapour attenuation for a one-year are presented.<>     

Analysis of 11 GHz slant path fade duration and fade slope

The letter presents results of an analysis of fade slope and fade duration data collected at 11 GHz within the framework of the OTS propagation experiments in Europe. Evidence is given of the fact that on a statistical basis, fade slope and fade duration are related. This could possibly be used in uplink power control systems.     

12-GHz slant-path propagation measurements

The performance of a statically hardware-compensated polarization measurement system is analysed, both, for linear and circular polarization. It is shown that such systems may affect the propagation measurements and hence their performance should be known prior to the evaluation of propagation data. With the results obtained, a propagation event recorded along theOts propagation path is analysed in terms of the differential propagation parameters, i.e. differential attenuation and differential phase shift.