Link Budget
An accounting of all gains and losses in a communications link from transmitter to receiver, used to determine whether a signal can be reliably received.
Explanation
A link budget calculates the total signal power arriving at a receiver and compares it to the minimum required for acceptable performance. It accounts for transmit power, antenna gains, free-space path loss, atmospheric absorption, polarization mismatch, implementation losses, and receiver noise. The result is the link margin — how much the actual signal exceeds the minimum required. A positive margin means the link works; a negative margin means it does not. Link budgets are essential for designing satellite communications systems, determining required ground station size, selecting modulation schemes, and setting data rates. Downlink budgets (satellite to ground) and uplink budgets (ground to satellite) are calculated separately. The link budget also determines which frequencies can be used — higher frequencies have more path loss but can support wider bandwidths.
Why It Matters
The link budget determines whether a satellite can communicate at all. It drives the design of antennas, amplifiers, and ground stations, and ultimately constrains data rates and coverage quality.
Concept Map
How Link Budget connects to other glossary terms:
Frequently Asked Questions
What happens if the link budget is negative?
The signal is too weak to be reliably received. Data may be lost, corrupted, or the link may not establish at all.
How does rain affect the link budget?
Rain causes additional attenuation, especially at Ka-band and higher frequencies. Link budgets include a rain fade margin to ensure connectivity in adverse weather.
Sources
Last updated: July 1, 2026