Cascaded Noise Figure Calculator
The Friis formula for cascaded noise figure shows that the first stage dominates. A low-noise amplifier (LNA) at the receiver front-end is critical — even a high-gain second stage contributes very little. This is why LNA placement matters.
Equations & Parameters ▸
\(F_{total} = F_1 + \dfrac{F_2-1}{G_1} + \dfrac{F_3-1}{G_1 G_2} + \cdots\)
| Gₙ | Gain of stage n (dB). Passive components have negative gain (loss = −gain). |
| NFₙ | Noise figure of stage n (dB). Higher NF = noisier stage. |
| Cascaded NF | Total system noise figure referred to the input. Dominated by first stage. |
| Total gain | Sum of all stage gains. |
Physical constants used
| c | Speed of light = 2.998×10⁸ m/s |
| µ₀ | Permeability of free space = 4π×10⁻⁷ H/m ≈ 1.2566×10⁻⁶ H/m |
| ε₀ | Permittivity of free space = 8.854×10⁻¹² F/m |
| k_B | Boltzmann constant = 1.381×10⁻²³ J/K |
| h | Planck constant = 6.626×10⁻³⁴ J·s |
| ¹H gyromagnetic ratio | γ/2π = 42.577 MHz/T |
Stage Configuration
Results
System
Cascaded noise figure—
Total gain—
Diagram