The design of polyphase-based IIR multiband filters

This paper addresses a new approach for the design of multiband filters with step like magnitude responses and extremely flat, weighted passbands down to μdBs. Our new technique can also be used for the multiband stepwise approximation of arbitrary filter magnitude responses with precise transition band control. One marked advantage of the technique is that our basic building blocks are the modified polyphase (W) filters. The points of transition from one flat-top to another, namely the multiple transition bands of our filter are completely free of cross-over oscillations. One other advantage of this technique is that we are not confined to employing IIRs only. To this end perfect reconstruction FIR filters can also be used. In both the FIR and IIR cases our technique is general purpose and works for both real and complex valued filter coefficient cases