[time-nuts] Phase noise confusion II

[Richard (Rick) Karlquist]

On 4/9/2020 5:05 PM, Didier Juges wrote:
> Perry,
> 
> Typically jitter is expressed in the time domain (so many ps peak to peak
> for instance)
> Phase noise is expressed as a power ratio in the frequency domain.
> Otherwise they usually represent the same phenomenon.
> 
> Didier
> 
> On Thu, Apr 9, 2020, 6:29 PM Perry Sandeen via time-nuts <

An alternate description is that jitter is measured over
a band of spectral frequencies that does not go to zero,
but might go to infinity.  There is always an implied
clock recovery loop that the the jitter is measured against.
The loop may itself affect the jitter measurement either
by cleaning up jitter or contributing to it.

Phase noise is expressed as a noise density in a 1 Hz bandwidth.
It has no particular lower limit.  Clock recovery doesn't
enter into it.

Although jitter is expressed in terms of time, it is not
a so-called time domain measurement like ADEV.  It is closely
related instead to phase noise.  There are 2 pi radians in
a unit interval.

Rick N6RK