Receiver DesignSystem Analysis

Noise Figure & Cascade Analysis

Every electronic amplifier adds a tiny bit of static — like each person in a telephone game adding confusion. The first amplifier matters most.

Interactive Signal Chain — Reorder Stages
The green bars show signal level and red bars show noise level at each stage output. The SNR label shows how noise figure degrades the signal-to-noise ratio.
LNAG=+15dBNF=1.5dBFilterG=-2dBNF=2dBMixerG=-6dBNF=6dBIF AmpG=+20dBNF=5dBInSNR≈34dBLNASNR≈33dBFilterSNR≈32dBMixerSNR≈32dBIF AmpSNR≈31dBSignalNoise

Cascade NF: 3.04 dB

Reorder stages to see how cascade NF changes. LNA first = lowest system NF.

LNAG=+15dB NF=1.5dB
FilterG=-2dB NF=2dB
MixerG=-6dB NF=6dB
IF AmpG=+20dB NF=5dB
Core Concepts

Quick Reference
Key noise figure formulas
Thermal noise floorN = kTB = −174 dBm/Hz
Noise factorF = SNR_in / SNR_out
Noise figureNF = 10 log₁₀(F)
Friis cascadeF = F₁ + (F₂−1)/G₁ + ...
Noise temperatureT_e = 290 × (F − 1) K
SensitivityS = −174 + NF + 10log(B) + SNR_min
Related Tools
Put these concepts to work

Noise Figure Calculator

Calculate cascade noise figure using the Friis formula for any chain of components

Noise Floor Calculator

Find the thermal noise floor for any bandwidth and temperature