Re: [Discuss-gnuradio] halfband in CVS

[Lamar Owen]

>> On Tue, Oct 25, 2005 at 12:16:09AM -0400, Lamar Owen wrote:
> With a decimation rate of 8 and a DDC center frequency at 10.7MHz, I see
> better than -10dB at the band edge now, which is a greater than 20dB
> improvement in flatness.  Very nice.

Attached are some captures of plots made with a slightly customized
usrp_fft.py (and older version, too; not sure if that impacts the curve
shapes).  The customization is changing the average_alpha to 0.001 as well
as the number of fft points to 1024, and the scales.

The curve shapes are quite interesting.  Perhaps tweaking of some
coefficients somewhere in the halfband verilog would make it flatter
across more decimation ratios?  The current best flatness is at a decim of
32, as is clearly visible in the plots.

-- 
Lamar Owen
Director of Information Technology
Pisgah Astronomical Research Institute
1 PARI Drive
Rosman, NC  28772
(828)862-5554
www.pari.edu