On Tue, 2015-07-21 at 12:01 -0400, address@hidden
wrote:
Message: 11
Date: Tue, 21 Jul 2015 11:47:40 +0200
From: Marcus M?ller <address@hidden>
To: address@hidden
Subject: Re: [Discuss-gnuradio] Run graph/ scheduler overhead
Message-ID: <address@hidden>
Content-Type: text/plain; charset=windows-1252; format=flowed
Hi Dennis,
if I read Fig 4 of [1] correctly, then you 32-delay DC blocker has a
passband starting at let's say 0.025 * f_sample.
I've gone ahead and clicked together a FIR filter that theoretically
should perform as well; its CPU consumption is... tolerable :)
Compare [2]; taps are in the PNG comment. Because this is so quick
and
dirt, I didn't bother to verify I really see 10MS/s throughput -- but
considering the most-used CPU core is tasked 40% of its time only, I
think that's a feasible assumption; plus, you can probably go
further,
if the filter performance doesn't match your needs -- I found that
for
filters > 100taps numerical accuracy of single precision floating
point
arithmetics starts taking its toll, so your amplitude response will
not
100% be what gr_filter_design shows. Verify with a long averaging Qt
frequency sink or so.
Best regards,
Marcus
[1]
http://www.ingelec.uns.edu.ar/pds2803/materiales/articulos/04472252.pdf
[2] http://i.imgur.com/Qmx9q96.png
Hmmm.
Since this is ADS-B and phase doesn't matter, how about a differentiator
followed by a leaky integrator:
IIR filter:
Feedforward taps: [1.0 -1.0]
Feedback taps: [1.0 -0.99]
4-taps. I have no idea how computationally efficient GnuRadio is at IIR
filters.
Need a steeper notch at DC, change the -0.99 to -0.9999 or whatever.
Regards,
Andy
On 21.07.2015 09:02, Dennis Glatting wrote:
On Mon, 2015-07-13 at 21:43 -0400, Tom Rondeau wrote:
On Mon, Jul 13, 2015 at 12:30 AM, West, Nathan
FYI and following up.
I simplified my graph (below). According to gr-perf-monitorx, and
gr-ctrlport-monitor agrees, 95% of the the time is spent in
dc_blocker_cc.
I haven't look at why but clearly that's a problem.
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