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Re: [Discuss-gnuradio] Rounding errors in PFB channelizer?


From: John Ackermann N8UR
Subject: Re: [Discuss-gnuradio] Rounding errors in PFB channelizer?
Date: Thu, 30 Nov 2017 14:19:11 -0500
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0



On 11/30/2017 02:08 PM, Müller, Marcus (CEL) wrote:
[ snip ]

You can do that (obviously, it works!), but I'd recommend you just use
a channelizer with N=125 instead of 117! Your channel map can be used
to ignore the channels you don't need (which seem to be the 4 upper and
lower "edge" ones), and by only increasing the workload of the PFB ever
so slightly (probably even actually decreasing it, because an 125=5³-
FFT is likely to be much more efficient than an 117=3²·13-FFT), you get
rid of the rational resampler, which not only brings more CPU load, but
also a resampling filter response that might have ripple and aliases.

Thanks for that suggestion, Marcus! I have the resampler version running right now but will change to use the channel count idea instead.

John



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