
214
P. Dewilde
The obvious choice for the A and B operator of the corresponding O matrix is given by:
E
~
A __ "~176
' B2 :
I
,9 I
81
9
8 n
For the algebraic Hermite-Fejer problem, which is an extension of the previous case to
higher multiplicities, the choice is as follows:
A
V~ I
v;( l
I
I
V~(k-~)
B1
B2
V~ I
~ o ... o ~ o...
THE MODEL REDUCTION PROBLEM
Here we start out with a high order model for a given T, in output normal form (for
convenience, we assume T to be strictly causal),
T = BZ(I - AZ)-IC
with
AA* -4- CC* =
I. Let, furthermore, be given a hermitian, diagonal matrix r, ...