Tropospheric amplitude spectra due to absorption and scattering in earth-space paths
Abstract
Results are presented of experimental measurements of the temporal frequency spectrum of amplitude scintillations on a low-elevation satellite path (U.K. - Indian Ocean) at X-band. The shape of the spectrum is examined and found to be quite variable. The high-frequency spectral roll-off is shown to often display two slopes where a region of small slope is followed by another of steeper slope, with a value close to that for a Kolmogorov spectrum. The spectra display a corner frequency in the region of 0.06 Hz. In addition a distinct upturn is shown to be at times observed in the low frequency region of the spectrum, occurring at a frequency of around 0.005 Hz. A wide-based study of this frequency suggests that at X-band this upturn is not due to a gaseous absorption process but rather caused by variable attenuation due to rain, or rain clouds crossing the path. Theoretical expressions are presented which take into account the large path lengths encountered on low-elevation links and the applicability to slant paths of some of the standard theoretical expressions developed for horizontal paths is discussed.
- Publication:
-
4th International Conference on Antennas and Propagation (ICAP 85)
- Pub Date:
- 1985
- Bibcode:
- 1985anpr.conf...77B
- Keywords:
-
- Atmospheric Attenuation;
- Fresnel Region;
- Refractivity;
- Scattering Amplitude;
- Tropospheric Scattering;
- Wave Propagation;
- Gases;
- Kolmogoroff Theory;
- Communications and Radar