Noise Figure by Y-Factor
The Y-factor method measures noise figure by switching a calibrated noise source between its hot (on) and cold (off) states and taking the ratio Y of the two output powers. With the source's excess noise ratio (ENR), that ratio gives the device's noise factor, noise figure, and equivalent input noise temperature.
Equations & Parameters ▸
\(F = \dfrac{\text{ENR}}{Y - 1} \qquad NF = 10\log_{10}F \qquad T_e = T_0\,(F - 1),\ \ T_0 = 290\,\text{K}\)
| ENR | Excess noise ratio of the source (dB). Entered in dB; converted to linear internally. |
| Y | Ratio of hot to cold output power (dB). Y > 1 (i.e. > 0 dB). |
| F | Noise factor (linear); NF is its value in dB. |
| Te | Equivalent input noise temperature (K), referenced to T₀ = 290 K. |
References: Keysight, App. Note 57-1, Fundamentals of RF and Microwave Noise Figure Measurements. · D. M. Pozar, Microwave Engineering, 4th ed., Wiley, 2012.
Inputs
dB
Noise-source ENRdB
Hot/cold power ratioResults
Noise figure
Noise figure NF—
Noise factor F—
Temperature
Noise temp. Te—
Diagram