[time-nuts] Practical relation between Phase Noise and ADEV

[Erik Kaashoek]

Both ADEV and Phase Noise can be measured around 1 to 10Hz so for my own 
understanding I made an empirical graph that relates a certain phase 
noise with its impact on the ADEV to allow checking for consistency in 
measurements.
All data mentioned is only correct for a signal at 10MHz
The table was made by generating a 10MHz test signal with just the right 
level of phase noise at the wanted frequency and measuring the ADEV of 
the test signal. Of course it should be possible to calculate this 
relation but these calculations are not my strongest point.
And I did not verify how the summing of noise impacts the total ADEV
Phase noise with frequency f has maximum contribution to ADEV at 
frequency f*2.
Phase noise of -60dBc at 1Hz contributes maximum 1E-10 to ADEV at 0.5Hz
Every 20dB of decrease in noise level decreases ADEV contribution with a 
factor 10
Every factor 10 increase in frequency increases the ADEV contribution 
with a factor 10.
A simple graph showing the relation can be found here: 
http://athome.kaashoek.com/time-nuts/PNvsADEV.PNG
Erik.