On the invariance of second-order modes under frequency transformation in 2-D separable denominator digital filters
Masaki Kawamata, Shunsuke Koshita · 2003
This paper discusses the invariance of the second-order modes of 2-D separable denominator digital filters under frequency transformation. It is proved that the second-order modes of 2-D separable denominator digital filters are not invariant under all frequency transformations, but invariant under specific frequency transformations of which transfer functions are strictly proper.