Hi Laura, Sorry for the delay in responding.
The diagram given in the PFB memo is correct, but the equation isn't (I forget how I derived it and can't find my notes). I've updated the page with the corrected equation. Thanks for pointing this out, and please let me know what you think. Cheers, Jayanth On Wed, Mar 19, 2014 at 2:21 PM, Vertatschitsch, Laura E. < [email protected]> wrote: > Hey guys, > > I was checking out the polyphase filter bank > <https://casper.berkeley.edu/wiki/The_Polyphase_Filter_Bank_Technique>page > and I have a question. There appears to be a difference between the y(m) > mathematical description and the associated diagram in Figure 4. Namely, > the y(m) claimed by the caption of Figure 4 is still to me a function of n, > rather than m. There are 2 sums in the y(m) mathematical derivation, but > clearly only 1 summing operation (on each parallel stream) in Figure 4. It > seems to me that this figure is only illustrating the inner summation of > the mathematics, and in fact summing the outputs is still a necessary step > to produce a signal consistent with y(m) in the math. > > If I am missing something I apologize. My DSP background is from EE, so > actually thinking of this as weighted overlap add was informative to me, > but I still find myself needing to re-derive things carefully to understand > subtle differences between the EE and astronomy signal processing worlds. > > --Laura >
