A digital bandpass/bandstop complementary equalization filter with independent tuning characteristics

A discrete-time realization of first-order (shelving) and second-order equalization filters is developed, providing bandpass/bandstop magnitude-complementary transfer functions. The bandpass transfer function is turned into a complementary one, and vice versa, switching between two structures that share a common allpass section containing the state variables of the equalizer. The present realization is an alternative to existing solutions, particularly in applications where the equalization parameters are dynamically varied.