RX Noise Figure

\( NF = 10log[{{SNR_{input}} \over {SNR_{output}}}] _{T=T_0=290K} \)

Noise Figure Measurement Methods:

  1. Gain Method or Cold Noise Method

    \( NF_{dB} = 10 log [{P_{cold} \over {kTBG}}] \)

    \( NF_{dB} = P_{cold} - (-174dBm/Hz) - 10log_{10}(B) - G_{dB} \) $$\ \begin{align} B& = bandwidth \\ P_{cold}& = cold\ noise\ power\ measurement \\ kT& = thermal\ noise\ power\ associated\ with\ 290K = (1.38*10^{23}J/K * 290K) = -174dBm/Hz \\\ \end{align} $$

  2. Y-Factor Method

    \( NF = 10log[{ENR \over {Y-1}}] \)

    $$\ ENR = Excess\ noise\ ratio\ of\ the\ noise\ source $$

    \( Y = {P_{hot} \over P_{cold}} \)

    \( NF_{dB} = ENR_{dB} - (P_{hot, dB} - P_{cold, dB}) \)

References:

  1. KF5OBS #32: Noise Figure Measurement (Gain Method)
  2. KF5OBS #34: Noise Figure Measurement (Y Factor Method)
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