Mumbai University > EXTC > Sem 8 > Satellite Communication and Networks

Marks: 8M

To satisfy the objectives of reliability and specified availability, it is necessary to back up the radio-frequency equipment of an earth station.

As far as the input stages are concerned, the use of a redundant receiver is normal except for small stations which usually do not incorporate redundancy. Since the operation of the station is monitored, it is rare to have more than one standby system since maintenance of the station is guaranteed.

For the output stages, the redundancy arrangement depends on the type of coupling. With pre coupling of the carriers, the power amplifier (single except in the case of mixed coupling) is usually replicated. With post-coupling of the carriers, it is not useful to replicate each carrier amplifier and the use of back-up equipment shared among several active units is usual.

The basic elements for a redundant earth station are shown in Fig. In connection with transponders, redundancy means that certain units are duplicated. A duplicate, or redundant, unit is automatically switched into a circuit to replace a corresponding unit that has failed. Redundant units are shown by dashed lines in Fig.