Quantization effects in the polyphase N-path IIR structure

Polyphase IIR structures have proved themselves very attractive for very high performance filters that can be designed using very few coefficients. This combined with their low sensitivity to coefficient quantization in comparison to standard FIR and IIR structures makes them very applicable for very fast filtering when implemented in fixed point arithmetic. However, although the mathematical description is very simple, there exist a number of ways to implement such filters. In this paper we take all these different implementation structures and analyze the rounding noise originating from the limited arithmetic wordlength of the mathematical operators and check the internal data growth within the structure.