Angle-of-arrival Fluctuations due to Meteorological Conditions in the Diffraction Zone of C-band Radio Waves, Propagated over the Ground Surface

摘要

Results of direct measurements of slowly fluctuating C-band radio wave angles-of-arrival are described. The measurements were done using a conical scan radar over paths about 36 km long during one winter month near Tomsk. As a target there was used a corner reflector installed at the height of 48 m on a wood tower. Meteorological data and data concerning earth's surface are used to analyze mean angles of elevation and azimuth, observed at 15 min intervals. These results are used to predict radar tracking errors by angle of elevation and azimuth caused by earth's surface and troposphere refraction. The accuracy of radar angular measurements at low grazing angles is not good due to reflections from rough surfaces, diffraction on obstacles and radio wave refraction. The angular measurement errors have quick and slow fluctuations. The quick fluctuations are about zero as a result of averaging on the intervals of measurement. The slow fluctuations are not averaged on the intervals of measurement and provide displacements of angle estimates. These errors are important for radar tracking in case of far away targets and obstacles near the radar. In this paper the results of direct measurements of angles-of-arrival of slowly fluctuating C-band radio waves are described. As a target there was used a corner reflector. The measurements were done using conical scan radar over paths about 36 km long during one winter month near Tomsk, West Siberia.