On 18/02/2025 19:26, Brendan Horsfield wrote:
I thought your name sounded familiar! 🙂
Overall the X310+UBX-160 appears to be a good fit to our
requirements. My original question was really about ensuring that our
host PC & network interface have sufficient bandwidth to ingest the IQ
data from a pair of UBX-160s. It would be nice (although not
essential) if we could run one channel at 100 Msps, and the other at
200 Msps, to reduce the bandwidth requirements on the backend hardware.
You'd need to have separate streamers to support two different sample
rates, and two 10Gbe interfaces.
But in terms of "what kind of PC hardware do I need?". There's no
closed-form answer to that question. There's no
handy-dandy "engineering worksheet" that tells you how much "grunt"
you need for different DSP "flows" at
a given sample-rate--so very much depends on what you're doing, and
how you're doing it. Generally, as you scale up
in sample-rate, you have to scale up in:
o CPU base clock rate
o Memory bandwidth
o Number of CPUs
On Wed, 19 Feb 2025 at 10:17, Marcus D. Leech
<patchvonbr...@gmail.com> wrote:
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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