Uplink and Downlink

 

Uplink and downlink frequencies

• The range of frequencies used for the satellite communication is a form 3 to 30 GHz  I.e. microwave range.
• Uplink and downlink frequencies shown in figure.

• The uplink frequency can be defined as the frequency used by signal transmitted from transmitting earth station towards the satellite.
• Appling frequencies are generally higher than downlink frequency.
• Generally the frequency band from 5. 9 to 6. 4 GHz are used for uplink transmission.
• The downlink frequency can be defined as the frequency of signal which is transmitted from satellite to earth station.
• Generally downlink frequency range is between 3. 7 to 4. 2 GHz.
• In the satellite the signals are down converted to a frequency of downlink.
• In the satellite transponder is a combination of transmitter receiver which town converts the signals as well as receivers the signals from earth station.

• Mainly the functions of transponder is amplification of Signal and frequency transmission.
• The frequency transmission is a necessary because transponder can not transmit and receive on the same frequency.
• A satellite is not review relay station.
• it does not just reflect signal and it received them process them down convert them and transmits them.
• On -board is satellite has a number of transponders.
• Transponders not only transmit video but also mono and stereo-audio, telephone message, news reports and data.
• The average operating power of transponders is a few watts. The number of transponder on a satellite is a related to bandwidth requirements.
• e.g. For  video use the bandwidth requirement of a transponder is a 40MHz total bandwidth available 500MHz. if one use up to 500/40  i.e. 12 transponders.

 

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