Calculadora de Figura de Ruido en Cascada Gratis
Calcula la figura de ruido total de etapas en cascada usando la fórmula de Friis.
Total Noise Figure
1.62 dB
Total Noise Figure vs Stage 1 Noise Figure
Fórmula
## Friis Noise Formula for Cascaded Stages The overall noise figure of a chain is dominated by the first stage, especially if it has high gain. ### Formula **F_total = F_1 + (F_2 - 1)/G_1 + (F_3 - 1)/(G_1 x G_2)** All values in linear (not dB). Convert: F = 10^(NF_dB/10), G = 10^(Gain_dB/10). **NF_total(dB) = 10 x log10(F_total)** This is why low-noise amplifiers (LNAs) are placed at the front of receiver chains.
Ejemplo Resuelto
Three-stage receiver: LNA (1.5 dB NF, 20 dB gain), mixer (6 dB NF, 10 dB gain), IF amp (10 dB NF).
- 01F1 = 10^(1.5/10) = 1.413, G1 = 10^(20/10) = 100
- 02F2 = 10^(6/10) = 3.981, G2 = 10^(10/10) = 10
- 03F3 = 10^(10/10) = 10
- 04F_total = 1.413 + (3.981-1)/100 + (10-1)/(100 x 10) = 1.413 + 0.030 + 0.009 = 1.452
- 05NF_total = 10 x log10(1.452) = 1.62 dB
Preguntas Frecuentes
Why does the first stage matter most?
The noise contributions of later stages are divided by the gain of all preceding stages. High first-stage gain makes later stages negligible.
What is a good noise figure for an LNA?
For sensitive receivers, LNA noise figures below 1 dB are common. Consumer Wi-Fi receivers may have 3-5 dB.
What is noise temperature?
An equivalent way to express noise. T_eq = 290 x (F - 1) Kelvin, where F is the linear noise factor.
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