Leeson's Oscillator Noise Model

Estimate single sideband oscillator noise characteristics.

Ln (dBc)


Click or touch the plot above to read the values

Δf = - frequency distance from the oscillator frequency
Ln = - single-sideband phase noise spectrum
QL= - Q-factor of the resonator

Enter oscillation frequency to find Q-factor of the resonator, you can use SI suffixes in your numbers e.g. 10k would be 10 kilo. Capitalization matters, as 1m would be 1 milli and 1M would be 1 mega.


Calculations are based on the Leeson oscillator noise model, which gets two asymptotic appearances dependent on whether fa is smaller or larger than half the 3dB bandwidth BW3dB of the resonance circuit in the oscillator.

Ln (Δf)=Feff k T / 2Po {1+fa/Δf} {1+(BW3dB/2Δf)2}  [Hz-1],


Feff - effective noise figure that describes the amplifier under large signal sinusoidal excitation.

Po - output power of the oscillator.

T0 = 290 K, k1.38×10−23 J/K.