System based on tropospheric scattering

The troposphere is the lowest 10 km part of the atmosphere. The inhomogenities within the common beam volume of the transmit and receive antenna act as sources scattering the electromagnetic waves into all directions of space. Thus components will be generated establishing coupling between transmitter and receiver. Tropospheric links are based on this weak coupling mechanism [2.1.7.4]. The first troposcatter link has been put into operation in 1953.

It follows from the geometry of the link that distances of up to 400 to 500 km can be spanned. This is why troposcatter links have been applied at places that were hardly accessible such as links connecting oil well islands with the mainland, links within deserts and jungles, or links for military communication (before the large-scale use of inexpensive satellite links). These links are operating in the 350 MHz to 6 GHz range within the bands allocated by the ITU. The parameters of the radio channel require extremely high-gain antennas and transmitting powers, further the application of multiple diversity systems such as frequency and space diversity, angle and frequency diversity. The capacity of the transmitted information is limited by propagation time differences over the scattering volume. Typical values are the transmission of 120 to 240 voice channels in FDM-FM systems, or 8 to 12 Mb/s bit rates in FSK or PSK systems.

0 0

Post a comment