This question appears in Mumbai University > Satellite Communication and Network subject

Marks: 5 M

Year: Dec 2014

• The downlink frequency band of 12.2 to 12.7 GHz spans a range of 500MHz which accommodates 32TV/FM channels each of which is 24MHz wide.
• The receiving horn feeds into a low noise block (LNB). The LNB provides gain for the broadband 12GHz signal and then converts the signal to a lower frequency range so that a low cost coaxial cable can be used as feeder to the indoor unit.
• The standard frequency range of this down converted signal is 950 to 1450MHz. This signal is fed to the indoor unit. It is further amplified and passed to a tracking filter which selects the desired channel.
• The selected channel is again down converted, this time from 950 -1450 MHz range to a fixed intermediate frequency usually 70MHz although other values in the very high frequency (VHF) range are also used.
• The 70MHz amplifier amplifies the signal upto the levels required for demodulation.
• Hence In most satellite TV receivers the first IF band is converted to a second fixed IF.