[time-nuts] AM vs PM noise of signal sources

Attila Kinali attila at kinali.ch
Fri Jan 5 06:27:13 EST 2018


On Tue, 2 Jan 2018 23:34:18 +0100
Magnus Danielson <magnus at rubidium.dyndns.org> wrote:

[About AM noise being of equal power as PM noise]

> Now, for actual sources this is no longer true. The AM noise can be much
> higher, which is why it can be a real danger to the PM noise if there is
> a AM to PM noise conversion. One source of such conversion can be the
> amplification stage, but another could be a mistuned filter, which have
> different amplitudes of the side-bands, which can create conversion as
> the balance does not balance the same way anymore.

Yes, exactly. I am currently trying to understand how noise affects
circuits an how input and circuit noise get converted to output noise.
First assumption that needs to be dropped is that the noise processes
is purely additive and independent of the signal. This means that a
noise process does not anymore produce equal AM and PM power.

I think I have a 90% solution of the noise processes and conversions
in a sine-to-square converter (aka zero-crossing detector, aka comparator).
But there is one process that keeps puzzling me. I think I know where in
the circuit it must come from, but I have no explanation as to how it happens.


				Attila Kinali
-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
                 -- Miss Matheson, The Diamond Age, Neil Stephenson


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