Grouped B-spline functions for the design of improved FIR filters

The design of the finite impulse response (FIR) digital filters with linear phase is considered by cascading a prototype filter with complementary comb filters. The minimum attenuation in the stop band is increased and the complexity of implementation is reduced, because the complementary comb filters contain only adders and storage units. The prototype filter is designed by using grouped B-spline windows and a modified transfer function. In the proposed method, the composite filter maintains the linear phase, because the complementary comb filters have linear phase responses.