On 18/02/2025 19:13, Brendan Horsfield wrote:
Thanks for the suggestion about the noise source -- that's what I
would normally do. Unfortunately I haven't actually purchased the
hardware yet -- I was hoping to clarify this issue before raising a
purchase order.
Perhaps I should follow this up with one of the application engineers
at NI? They might have access to an X310+UBX-160 system that they can
use to answer my question directly.
Thanks again for your help in this matter.
Regards,
Brendan.
I actually do work for NI on USRP devices (on a very very very part-time
basis). My X310 is currently elsewhere, and not populated
with a UBX-160.
On Wed, 19 Feb 2025 at 09:55, Marcus D. Leech
<patchvonbr...@gmail.com> wrote:
On 18/02/2025 18:45, Brendan Horsfield wrote:
Yes, I assumed that was the case. However, it is not clear from
the X300 documentation how sharp those filters are. Can you tell
me how wide the transition band is at the lower sample rates?
To give you some context, I would like to use an X300 (or X310)
with a UBX-160 daughterboard to digitise the entire 2.4 GHz Wi-Fi
band, which is 83.5 MHz wide. Ideally I would like to use a
sample rate of 100 Msps to minimise the data rate between the
USRP and the host PC. However, before I do this I need to be
certain that the usable bandwidth at this sample rate will be
greater than 83.5 MHz. Is this information documented somewhere?
It somewhat depends on the decimation. If the decimation has a
factor of two or 4, the edge roll-off is fairly sharp. Otherwise,
there's a half-band filter in-place that causes a less-desirable
pass-band.
But I don't know, precisely, what the transition band is in the
"nicer" filter shapes.
If you have an X310+UBX-160, you can always just use a noise
source, and measure it yourself to see if it's appropriate for
your application.
On Tue, 18 Feb 2025 at 23:11, Marcus D Leech
<patchvonbr...@gmail.com> wrote:
There will always be some edge roll off. Decimation includes
filtering and those filters cannot be infinitely steep.
Sent from my iPhone
> On Feb 18, 2025, at 2:12 AM, Brendan Horsfield
<brendan.horsfi...@vectalabs.com> wrote:
>
>
> Hi All,
>
> I have a question about the usable bandwidth of the X300
USRP / UBX-160 daughterboard combo at sampling rates below
200 Msps:
>
> As I understand it, the UBX-160 receiver has an analog
(hardware) filter before the ADC that limits the usable
bandwidth to 160 MHz, while the ADC runs at 200 Msps.
Therefore the usable bandwidth is around 80% of the sample rate.
>
> My question is: What is the usable bandwidth at lower
sampling rates? Does the 80% factor always apply?
>
> For example, if I set the decimation factor to 4, so that
my sampling rate is 50 Msps, does this mean that the usable
bandwidth will be 40 MHz?
>
> Thanks & Regards,
> Brendan.
>
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