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