Re: [Discuss-gnuradio] USRP2 Halfband filter coefficients help

[Sebastiaan Heunis]

Hi

I think Brian is just referring to the fact that you can see that the
HBFs are implemented as symmetric FIR filters (the coefficients).  A
HBF is just a special filter that is designed so that the cutoff
frequency will always be at fs/2, so if you filter with it and
decimate by 2 afterwards (which is why you would use an HBF), you
don't get aliasing.  Also, the decimation in the CIC filters can be
set to a wide range of values, so the HBF will always have to cut at
fs/2 regardless of the decimation in the CIC.  From what I've read,
Goodman and Carey came up with them so you can probably look for some
papers if you're interested.

Sebastiaan

-- 
Sebastiaan Heunis
Radar Remote Sensing Group, University of Cape Town, South Africa
Tel:  +27 72 950 9370