Point taken. At this stage we are mainly interested in straight IQ recording & playback with minimal processing. However, in the future it would be desirable to be able to display a real-time spectrum trace & waterfall plot during recording/playback, using GNU Radio or something like it.
As you suggest, I am assuming our host machine will need a dual-10Gbe adaptor card and a high-spec CPU, memory, SSD etc. This is a complex procurement exercise all by itself. On Wed, 19 Feb 2025 at 10:58, Marcus D. Leech <patchvonbr...@gmail.com> wrote: > 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. >>>> > >>>> > _______________________________________________ >>>> > USRP-users mailing list -- usrp-users@lists.ettus.com >>>> > To unsubscribe send an email to usrp-users-le...@lists.ettus.com >>>> >>> >>> >> >
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