Randy Yates wrote:
> Jim Thomas <[email protected]> writes:
[snip]
>>Again, I'm allowing ample room for the possibility that I'm wrong, so
>>don't be shy! Is your equation correct?
>
>
> Nope! You're right. I had a sign problem in the x's. This corrects that problem (hopefully
> there are no others!):
>
> y[n] = x[n*M - 0*M - 0] * h[ 0*M + 0] + x[n*M - 0*M - 1] * h[ 0*M + 1] + ... + x[n*M - 0*M - (M-1)] * h[ 0*M + (M-1)]
> + x[n*M - 1*M - 0] * h[ 1*M + 0] + x[n*M - 1*M - 1] * h[ 1*M + 1] + ... + x[n*M - 1*M - (M-1)] * h[ 1*M + (M-1)]
> + ...
> + x[n*M - (K-1)*M - 0] * h[(K-1)*M + 0] + x[n*M - (K-1)*M - 1] * h[(K-1)*M + 1] + ... + x[n*M - (K-1)*M - (M-1)] * h[(K-1)*M + (M-1)]
>
> Thanks for the correction, Jim.

That's better, and now I see what you mean. But... it seems to me that
arranging the filter equation into rows and columns like this is somewhat
artificial.

At this point I'm just going to confuse people who already understand polyphase
filters but aren't confident in their understanding, and for that, I apologize
in advance. I guess I'm firmly in that same camp.

Each value of y depends on every filter tap, so I still don't see why it's
polyphase. If this is polyphase, aren't ALL FIRs polyphase?

--
Jim Thomas Principal Applications Engineer Bittware, Inc
[email protected] http://www.bittware.com (603) 226-0404 x536
Getting an inch of snow is like winning ten cents in the lottery - Calvin