It is well known that for a digital filter of order n the number of nontriv
ial parameters in the classical optimal state-space realizations is proport
ional to n(2). In this paper, a new structure is proposed for digital filte
r implementation. This structure possesses 5n - 1 nontrivial parameters and
is shown to be equivalent to the discrete-time counterpart of the well-kno
wn orthonormal ladder filter in [13], A new property of this ladder filter
is revealed. The performance of the proposed structure is analyzed. Express
ions for evaluating the sensitivity measure and the roundoff noise gain are
derived. A numerical example is presented to illustrate the design procedu
re. Simulations show that the performance of the proposed structure is almo
st the same as that of the fully parameterized optimal realizations.