Why does the uplink in communication satellites normally operate at a higher frequency than the downlink?

Introduction / Context:
In satellite communication, uplink and downlink frequencies are chosen carefully. Typically, uplinks use higher frequencies (e.g., 6 GHz for C-band uplink vs 4 GHz for downlink) because of differences in attenuation and power availability.

Given Data / Assumptions:

• Uplink power transmitted from Earth station is much higher than satellite power capability.
• Downlink must reach many users with limited satellite power.
• Atmospheric attenuation increases with frequency.

Concept / Approach:
Since Earth stations can generate high-power signals, uplinks can be sent at higher frequencies (with higher attenuation). Satellites, with limited power, use lower frequencies for downlinks to ensure signals reach users reliably.

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