[time-nuts] Spice simulation of PSRR and phase noise

Bruce Griffiths bruce.griffiths at xtra.co.nz
Sun Oct 22 18:23:17 EDT 2017


One has to provide noise models that work with the Spice transient simulation for all devices including resistors. Random number generators can be used but they need to be independent and must not repeat during the entire simulation.

Bruce

> 
>     On 23 October 2017 at 10:25 Bruce Griffiths <bruce.griffiths at xtra.co.nz> wrote:
> 
>     If one for example wishes to estimate PN down to an offset of 1Hz then an equivalent filter noise bandwidth of 0.1Hz or perhaps less is desirable (the PN spectrum at low offsets is far from flat). To achive accurate noise estimates a simulation time of at least 100 x the reciprocal of the equivalent noise bandwidth is required. The resultant simulation for 1000 sec or more takes considerably longer than 1000 sec to run.
> 
>     Bruce
> 
>         > > 
> >         On 23 October 2017 at 03:23 Dana Whitlow <k8yumdoober at gmail.com> wrote:
> > 
> >         Hello Attila,
> > 
> >         It seems to me that an AC simulation could never work since the
> >         very generation of phase noise by the mechanisms that matter is
> >         a modulation process at heart, automatically forcing one into the
> >         realm of transient simulations.
> > 
> >         But I am surprised about the simulation times that you speak of.
> >         Would you be willing to post some information detailing your
> >         methodology and an example "simple" circuit?
> > 
> >         Dana
> > 
> >         On Sun, Oct 22, 2017 at 7:53 AM, Attila Kinali <attila at kinali.ch> wrote:
> > 
> >             > > > 
> > >                 > > > > 
> > > >                 Hi,
> > > > 
> > > >             > > > 
> > >             I have been looking into spice simulations of circuits, in particular
> > >             trying to extract PSRR and phase noise information. Unfortunatelly,
> > >             the obvious way of putting AC sources at the right places does not
> > >             work, as the (ideal) input signals are not small and drive the circuit
> > >             into non-linearities. Hence I have to do transient simulations.
> > >             But extracting PSRR and phase noise information out of a transient
> > >             simulation is cumbersome at best and takes a lot of simulation time
> > >             (we are talking about hours to days for simple circuits).
> > > 
> > >             I am looking for guidelines and hints how to speed things up.
> > >             Maybe even being able to use standard DC and AC analysis for the
> > >             circuit instead of transient. Unfortunately, my google-foo was not
> > >             strong enough to find approriate documentation.
> > > 
> > >             Does someone have any hints what I should read or search for?
> > > 
> > >             Thanks in advance
> > > 
> > >             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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> > >         > > 
> >     > 



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