For the general case of arbitrary , the basic idea is to decompose into its periodically interleaved subsequences, as indicated schematically in Fig.11.9. The polyphase decomposition into channels is given by
where the subphase filters are defined by
The signal can be obtained by passing through an advance of samples, followed by downsampling by the factor . as shown in Fig.11.10.
Type II Polyphase Decomposition