G/T Figure of Merit
G/T is the headline figure of merit of a receiving station — the antenna gain divided by the system noise temperature, in dB/K. A higher G/T means a more sensitive receive system and a better downlink. It combines the antenna gain, the noise the antenna picks up from the sky and ground, and the receiver's own noise (from its noise figure).
Equations & Parameters ▸
\(T_{\text{rx}} = T_0\,(F-1),\quad T_0 = 290\,\text{K}\)
\(T_{\text{sys}} = T_{\text{ant}} + T_{\text{rx}},\qquad G/T = G_{\text{dBi}} - 10\log_{10}T_{\text{sys}}\ \ (\text{dB/K})\)
\(T_{\text{sys}} = T_{\text{ant}} + T_{\text{rx}},\qquad G/T = G_{\text{dBi}} - 10\log_{10}T_{\text{sys}}\ \ (\text{dB/K})\)
| G | Antenna gain (dBi), referred to the same reference plane as Tsys. |
| Tant | Antenna noise temperature (K) — sky + ground pickup. |
| NF | Receiver noise figure (dB). Converted to a noise temperature Trx. |
| Tsys | System noise temperature = Tant + Trx. |
| G/T | Figure of merit (dB/K). Higher is better. |
References: T. Pratt, C. Bostian & J. Allnutt, Satellite Communications, 2nd ed., Wiley, 2003. · D. Roddy, Satellite Communications, 4th ed., McGraw-Hill, 2006.
Inputs
dBi
Receive gainK
Sky + grounddB
or Trx belowK
If NF blankResults
Figure of merit
G/T—
Noise temperature
Receiver Trx—
System Tsys—
Diagram