Re: [Discuss-gnuradio] [USRP-users] USRP DDC and GNURadio Bandwidth Problem

[Derek Kozel]

Hello Ali,

The bandwidth parameter will select the Analog RF filters where possible. For the X310 the daughterboards do not have configurable filters so you will have to add a lowpass filter to your flowgraph.

Regards,

Derek

On Thu, May 17, 2018 at 2:10 PM, Ali via USRP-users <address@hidden> wrote:

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 <address@hidden>:

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) <address@hidden> 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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