Beginning with a restatement of Eq.
(
4.9),
we can express each FIR coefficient
as a vector
expression:
Making a rowvector out of the FIR coefficients gives
or
We may now choose a set of parameter values
over which an optimum approximation is desired, yielding
the
matrix equation

(5.11) 
where
and
Equation (
4.11) may be solved for the polynomialcoefficient
matrix
by usual
leastsquares methods. For example, in the unweighted
case, with
, we have
Note that this formulation is valid for finding the Farrow
coefficients of any
thorder variable
FIR filter parametrized by a
single variable
.
Lagrange interpolation is a special case
corresponding to a particular choice of
.
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