gEDA-user: analysis of periodically varying systems

[mcmahill@mtl.mit.edu]

anyone know if the following analysis can be easily automated with
ng-spice (or berkeley spice3) or acs?  I want to

1) compute the large signal time domain response of a circuit over one
period of either a driving source, or in the case of an oscillator a
period of the oscillation.  Note that I want this period to be after any
initial transients have died out so I probably need to actually simulate
many periods.  


2) save the entire state of the circuit at several time points in that one
period.


3) now at each of those time points, i want to take the saved state and do
a small signal AC analysis with the circuit linearized about that
particular state.  Actually, i'm really interested in doing a small signal
noise analysis so in actuality this will be many AC analyses (1 from each
noise source to the output).

4) finally i'd like to be able to retrieve each of these frequency
responses into something like scilab or matlab where I can do 2-D fourier
transforms on the family of transfer functions.  Ie, my independent
variables are frequency and what phase of the initial period and the
dependent variable is the complex gain at that frequency and phase.


so is this easily automated or will this take a zillion manual steps along
the way?

Thanks for any suggestions.

-Dan

ps, for the interested reader, this is whats needed for accurate noise
analysis of circuits like mixers and oscillators where a) the noise
sources vary periodically (ie shot noise) and b) the transfer functions
from noise sources to output vary periodically (ie, during part of the
period some devices may be off which isolate some noise sources from the
output).