Subject: conjugate poles/zeros for the laplace and zi
From: Martin O'Leary (oleary@cadence.com)
Date: Mon Feb 26 2001 - 17:17:18 PST
Ian,
at the last meeting we discussed changing the LRM in regard to
the handling of conjugate poles/zeros for the laplace and zi
filters.
If I remember the proposal correctly, it was to change section
4.4.11.1 so that the sentence;
"If a root is complex, its conjugate shall also be present."
to something like;
"If a root is complex, its conjugate may be present. It the
conjugate is not present, it will be automatically added"
There are a couple of problems with this;
1. The order of the filter can no longer be determined by looking
at the size of the vectors passed as arguments. This will make
it more difficult to implement the laplace function.
2. The transfer function description assumes that all the conjugates
are specified in the vector so if we are going to allow simulators
to fill in the missing conjugates, we will have to change more
than just one sentence.
Another thing to be noted is that laplace takes a tolerance argument.
The text doesn't seem to be clear about what it used for.
If we don't allow the simulator to fill in the missing conjugates,
perhaps the tolerance argument could be used to determine if two
complex numbers are close enough to be considered conjugates?
--Martin
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