Monday, July 25, 2011

Why uplink frequency is more than downlink frequency??????

1) On the Earth Station we have to penetrate the atmosphere to reach the satellite we need a lot of power to be generated...This is only possible with the help of High power transmitter circuits....which cannot be installed on the uplink is at higher freq with higher power.

2)Now as the frequency is increased the amount of interference caused by the atmosphore higher frequency signal has more signal energy in it can penetrate the atmosphere more easily...(the same reason why we use modulation with higher frequency)

3) Unwanted distortion like rain (main cause of attenuation), fog, other frequency in neighbourhood, etc cause we have to count to these factors and increase the frequency band to 100-1000Ghz range...

Now the Satellite is a small piece of equipment and needs to be light it cannot have high power amplifiers on board so by default the freq is lower than uplink...

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