Subject: Re: conjugate poles/zeros for the laplace and zi
From: Steve Hamm (Steve.Hamm@motorola.com)
Date: Tue Feb 27 2001 - 16:54:19 PST
---"Martin" == Martin O'Leary <oleary@cadence.com> writes:
Martin> Another thing to be noted is that laplace takes a tolerance argument.
Martin> The text doesn't seem to be clear about what it used for.
Martin> If we don't allow the simulator to fill in the missing conjugates,
Martin> perhaps the tolerance argument could be used to determine if two
Martin> complex numbers are close enough to be considered conjugates?
The tolerance serves the same function as the tolerance on ddt(),
since a typical way to implement Laplace transfer functions is to
unroll the Nth order differential equations into N 1st order
equations, equivalent to a string of ddt's. So if there's something
missing here, it's language in the LRM that points out that the
tolerance on laplace_xx() is equivalent in function to the tolerance
on ddt().
By the way, I don't think having conjugates automagically completed is
a good idea. If two roots are almost conjugates, we get in the game of
guessing whether they really are conjugates or are each half of a pair
to be completed. It is much clearer to error off and let the user be
explicit.
--Steve
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