2-DIMENSIONAL IFIR STRUCTURES USING GENERALIZED FACTORIZABLE FILTERS

In this paper we extend the idea of interpolated FIR (IFIR) filters to the two-dimensional (2-D) case, IFIR filters make for the reduction o f the computational weight, in the one-dimensional (1-D) case as well as in the 2-D case, In the 1-D case, the justification to such a perfo rmance advantage rests upon the relationship between filter order, tra nsition bandwidth and minimax errors for equiripple linear-phase filte rs. Even though no similar relation is known for minimax optimal multi dimensional filters, a qualitatively parallel behavior is shared by a class of suboptimal filters (''Generalized Factorizable'') recently in troduced by Chen and Vaidyanathan, for which an efficient implementati on exists, In our scheme, we use Generalized Factorizable filters for both the stages of the IFIR structure, An interesting problem peculiar to the multidimensional case is the choice of the sublattice which re presents the definition support of the first-stage (shaping) filter, W e present a strategy to choose (given the spectral support of the desi red frequency response) the optimal sublattice, and to design the seco nd-stage (interpolator) filter in order to achieve low overall computa tional weight.