Hello Ali,

That "bandwidth" parameter of the UHD Source/Sink block is used to adjust the 
'analog bandwidth' of the 'daughterboard'. Most of the daughterboards have a 
fixed analog bandwidth, so that parameter will be simply ignored in most cases 
('uhd_usrp_probe' will give the detailed info about the daughterboard). They 
are not used to configure digital filter taps.

If you want to add digital filters, you can simply add them on GNU Radio as 
seperate blocks. Software FIR/IIR filters are pretty slow, but they can keep up 
when the sampling rate is that low. If you want to push down some codes to the 
FPGA, consider RFNoC.


Regards,

Kyeong Su Shin


________________________________
보낸 사람: Ali <03do...@gmail.com> 대신 Discuss-gnuradio 
<discuss-gnuradio-bounces+ksshin=postech.ac...@gnu.org>
보낸 날짜: 2018년 5월 17일 목요일 오후 10:10:27
받는 사람: discuss-gnura...@gnu.org; usrp-users@lists.ettus.com
제목: Re: [Discuss-gnuradio] USRP DDC and GNURadio Bandwidth Problem

Hi,

I don't want my sampling rate to be 25 kHz. My sampling rate is already 195312 
Hz which is I think the minimum sampling rate for X310.

What I want is to filter out the frequencies which are at least 25 kHz away 
from my center frequency. For example I don't want to see a transmission which 
is 50 kHz away from my center frequency. Is it possible? How does the 
"bandwidth" parameter in UHD Source Block in GNURadio affect the captured IQ 
data?

Regards,
Ali

2018-05-14 12:19 GMT+03:00 Derek Kozel 
<derek.ko...@ettus.com<mailto:derek.ko...@ettus.com>>:
Hello Ali,

To extend what Marcus has said, here is a link to the UHD manual page about 
sample rates.
http://files.ettus.com/manual/page_general.html#general_sampleratenotes

Regards,
Derek

On Mon, May 14, 2018 at 8:54 AM, Müller, Marcus (CEL) 
<muel...@kit.edu<mailto:muel...@kit.edu>> wrote:
Hi Ali,

just like the console will tell you, 25 kS/s is simply impossible with
an X310; instead, the minimum possible rate was used.

You should probably just configure your X310 to get you e.g. 500 kS/s,
and then resample in digital domain. If you're hesitant to design your
own decimating filter, use the "rational resampler" block and configure
it to decimate by (500/25)=20.

Best regards,
Marcus

On Mon, 2018-05-14 at 10:18 +0300, Ali wrote:
> Hi to all,
>
> I am using GNURadio to control an X310. I want to get IQ samples for only 25 
> kHz bandwidth.
>
> When I wrote 25 kHz to the bandwidth line in UHD-Source block in GNURadio, I 
> still see the signals at 50 kHz or 75 kHz away from the center. My sampling 
> rate is 195312 Hz. When checked in MATLAB, the signals are there. It looks 
> like I cannot control the bandwidth with GNURadio.
>
> I suspected that there is not any DDC filter for this bandwidth. If it is so, 
> what is the minimum bandwidth for USRPs? Are the bandwidths that I can use 
> discrete? I am confused.
>
> Thanks in advance,
> Ali
>
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