Calculadora de Figura de Ruído — Formula

Friis Noise Figure Formula

Formula

F_total = F1 + (F2 - 1)/G1 + (F3 - 1)/(G1 x G2) + ...

All values in linear (not dB). The first stage dominates overall noise figure. Use a low-noise amplifier (LNA) first for best sensitivity.

Exemplo Resolvido

LNA (1.5 dB NF, 20 dB gain) followed by mixer (10 dB NF, 15 dB gain) and IF amp (15 dB NF).

  1. F1 = 10^(1.5/10) = 1.413
  2. F2 = 10^(10/10) = 10, G1 = 10^(20/10) = 100
  3. F3 = 10^(15/10) = 31.62, G2 = 10^(15/10) = 31.62
  4. F_total = 1.413 + (10-1)/100 + (31.62-1)/(100x31.62) = 1.413 + 0.09 + 0.0097 = 1.513
  5. NF = 10 x log10(1.513) = 1.80 dB