A link budget accounts for every gain and loss from transmitter to receiver to predict the received carrier power and link quality.
Key Formula — EIRP, path loss and received carrier
E I R P = P t + G t − L t ( d B W ) , L f s = 32.44 + 20 log 10 d k m + 20 log 10 f M H z ( d B ) , EIRP=P_t+G_t-L_t\ (dBW),\qquad
L_{fs}=32.44+20\log_{10}d_{km}+20\log_{10}f_{MHz}\ (dB), E I R P = P t + G t − L t ( d B W ) , L f s = 32.44 + 20 log 10 d k m + 20 log 10 f M H z ( d B ) , C = E I R P + G r − L f s − L o t h e r ( d B W ) . C=EIRP+G_r-L_{fs}-L_{other}\ (dBW). C = E I R P + G r − L f s − L o t h er ( d B W ) . [!IMPORTANT]
Key Formula — Carrier-to-noise density, C/N and E b / N 0 E_b/N_0 E b / N 0
C N 0 = E I R P + G T − L f s − L o t h e r + 228.6 ( d B H z ) , \frac{C}{N_0}=EIRP+\frac{G}{T}-L_{fs}-L_{other}+228.6\ (dBHz), N 0 C = E I R P + T G − L f s − L o t h er + 228.6 ( d B H z ) , C N = C N 0 − 10 log 10 B , E b N 0 = C N 0 − 10 log 10 R b . \frac{C}{N}=\frac{C}{N_0}-10\log_{10}B,\qquad
\frac{E_b}{N_0}=\frac{C}{N_0}-10\log_{10}R_b. N C = N 0 C − 10 log 10 B , N 0 E b = N 0 C − 10 log 10 R b . where − 228.6 = 10 log 10 k -228.6=10\log_{10}k − 228.6 = 10 log 10 k B B B R b R_b R b
Link-budget chain: uplink EIRP and losses to the satellite G / T G/T G / T G / T G/T G / T C / N 0 C/N_0 C / N 0
Loss Cause Free-space loss Spreading over the long path Atmospheric absorption Oxygen and water-vapour absorption Rain attenuation Rain scattering/absorption; severe at Ku/Ka Polarization loss Transmit/receive polarization mismatch Pointing loss Antenna not exactly on the satellite Feeder loss Waveguide/cable loss to the antenna Implementation loss Modem and hardware imperfections
Common satellite-link losses.
