Learning Forum

[Charlotte Blair]

Hi, why do we use different frequencies for uplink and downlink for satellite communications?

[rtk]

Hi - Satellites communications is made possible with transponders which can transmit and receive signals at the same time. Different frequencies are used for uplink and downlink to help minimize the interference between them. Generally the uplink frequency is greater than the downlink frequency.

[Charlotte Blair]

Why should uplink frequency be greater than the downlink frequency?

[VivekKamble]

Hi @cblair ,

Uplink is characterized with VSATs (satellite base station) as transmitter and satellite as receiver while it is opposite for the case of downlink. The attenuation of the signals increases with the frequency. Hence the transmitted power should be higher for a higher frequency signal. This requirement can be easily accomplished by the satellite base station when compared with the satellite. Satellite needs to be lighter weight and high power transmitter design can increase the overall satellite weight. Also, high power transmission can drain the available power resources of satellite. Hence uplink frequency is made greater than the downlink frequency.

Hope this helped!