Hi I am a little confused on what the notation of the following statement means.
$$ H_{k}(z)= H(W_{4}^{k} z), k = 0,...,3$$
It comes from a question in which I have designed a FIR low-pass filter $H(z)$ and my goal is to implement a DFT filter bank scheme like this:
Exchange $P(z)$ for $H(z)$ and k would correspond to the subscript of P and M in this case is equal to 4
I guess I am confused on how to find $H_{k}(z)$ or what exactly a polyphase filter is