Subfilters for narrowband linear phase bandpass filters

A computationally efficient realization for subfilters which can be used as building blocks for narrowband linear-phase bandpass filters is introduced. The proposed subfilters take care of the stopband and transition band, since they share the property that all their zeros lie on the unit circle. The subfilters exploit the generalized recursive running sum. These filters can be realized using a new multirate filter structure requiring in many cases only one general multiplier, which can be easily hardwired. Another advantage is that the resulting impulse response for the subfilters is exactly symmetric and finite. The attenuation characteristics of the subfilters can be further enhanced using special composite filter structures.