Hi Marcus, Thanks for the advice. So, I just tried an experiment to test out your suggestion, and came up with a puzzling result. I set the sample rate to 4 MHz, and the decimation in the integrate block to 4 MHz, and recorded data for about 5 seconds. Instead of getting about 5 samples out, I tried to read the file and was told that there were "no samples" in the file. I then tried setting the decimation to samp_rate / fft_size, and the result there was the same. Any thoughts on why this might be?
Thanks, Ellie On Sat, Aug 10, 2019 at 11:17 PM Marcus D. Leech <patchvonbr...@gmail.com> wrote: > On 08/10/2019 10:48 PM, Ellie White wrote: > > Hi Marcus, > > Thanks for your reply. I am not sure how the integration works, but if you > know how the Integrate block does the integration, then that is how my > flowgraph does it. I suspect it is "sum /reduce /dump" as you mentioned, > though perhaps we would need to investigate the Integrate block's source > code to be sure? Thanks in advance for any additional suggestions you might > have on this! > > Cheers, > Ellie > > Here's the documentation on the integrate block: > > https://wiki.gnuradio.org/index.php/Integrate > > So, if your samples are coming in at 1kHz, and you want 1 second of > integration time (and an output rate of 1Hz), you'd set the > "decimation" parameter to 1000. > > This is one of the reasons I prefer single-pole-IIR filters--since I can > do sample-rate reduction as a separate process, via keep-one-in-N. > > > > On Sat, Aug 10, 2019 at 7:37 PM Marcus D. Leech <patchvonbr...@gmail.com> > wrote: > >> On 08/10/2019 03:40 PM, Ellie White wrote: >> > Hi all, >> > >> > I hope you're doing well! Thanks again for your help with my questions >> > earlier this summer. I've got another thing to ask now; I am in the >> > process of configuring a system to record integrated spectra using the >> > attached flowgraph, and I am trying to determine how to integrate for, >> > say, 60 seconds -- if I want to do this, what should my decimation be, >> > and how do I calculate that? I have been able to approximate this by >> > trial and error, but I would like to know the calculation behind it. >> > >> > Thanks in advance for any advice you can provide, much appreciated. >> > Have a good afternoon! >> > >> > Cheers, >> > Ellie >> > >> It kind of depends on how you're doing integration. >> >> An approach that strictly does sum/reduce/dump then you need as many >> samples as would occur over your desired integration time. >> >> For a single pole IIR filter, it's a bit trickier, and you'd set the >> "Alpha" parameter to: >> >> e^sqrt(sample-rate*integraton-time) >> >> Which will approximate an R-C integrator with the given integration time. >> >> >> >> _______________________________________________ >> Discuss-gnuradio mailing list >> Discuss-gnuradio@gnu.org >> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >> > >
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