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From: | bob wole |
Subject: | Re: [Discuss-gnuradio] HELP! - Problem with radio application deploy |
Date: | Thu, 21 Nov 2013 11:41:16 +0500 |
> How do you determine the size of taps? How much of a difference does
> setting the transition width from 1MHz to 10MHz make?
>
Generally, the wider the transition width, the fewer taps.
You can use the "firdes" functions, which is what the low-pass filter
blocks call in gnuradio, then take their output into a variable and
have another variable be len(filter).
>
> On Tue, Nov 19, 2013 at 6:40 PM, Marcus D. Leech <address@hidden
> <mailto:address@hidden>> wrote:
>
> I really appreciate the detailed explanation. I tried running
> gr_filter_design last night and it asked me to install SciPy,
> which I did not feel like doing at that time. I will try using
> 1MHz for my band, which may help get rid of the real-time
> running issue.
>
> Again, I appreciate your help with this matter.
>
> Let's say you get a filter that's, oh, I dunno, 100 taps long.
> That filter has to process every sample, so, that's 5e7 X 100 taps, or
> roughly 5e9 FLOP/second. Just for that one filter. And your
> flow-graph is likely doing other things *and* it's having to get
> samples
> all the way through your network or USB stacks into the
> application layer as well, call that 100 instructions/sample. So,
> that's
> 5e7 x 100 = 5e9 OPS/second just to get your samples into the
> application. You're going to burn-up the cycles on your CPU pretty
> quickly at 50Msps, even for doing "trivial" things.
>
>
>
>
>
> --
> Marcus Leech
> Principal Investigator
> Shirleys Bay Radio Astronomy Consortium
> http://www.sbrac.org
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