[USRP-users] B200 RX Additional Functionality Questions

Derek Murphy cyrus104 at gmail.com
Sat Apr 4 15:32:24 EDT 2015


Thanks, that's great information. My millage right now on uhd and verilog
is very low. I will start to look into it.

I thought that since the ad9361 was the same then maybe the firmware could
be modified to use both the a:rx2 and a:tx/rx could be used at the same
time. The 30MHz limit is not a big deal because the signal is super narrow.
On Apr 4, 2015 3:13 PM, "Ian Buckley" <ianb at ionconcepts.com> wrote:

> Derek,
> (You are specifically talking about B200 right? Not B210?)
> In theory this can be done, but the stock FPGA image won't do it. You
> would want to use to use the radio in a 1 RX mode because this would allow
> the use of (upto) a 61.44MHz sample clock between radio and FPGA, rather
> than the 30.72MHz max when in a 2 RX mode. (B200 doesn't have 2 RX mode
> anyhow)
> You would then want to take the B210 FPGA design, strip out the TX DUC's
> and buffer RAM so that it would fit in the B200's smaller FPGA, and then
> make one small alteration so that both RX DDC's are fed from the same (1
> RX) sample bus. (At this point it would look very like the RX design of
> N210 with 2 RX DDC chains.).
> From there you have a few details to deal with in UHD (2 DDC's
> operational, but AD9364 delivering a single RX stream). And finally a flow
> graph that uses offset LO tuning such that you position the LO at (for
> example) 22.5MHz between your frequencies of interest and tune the 2
> CORDICs to +/- 22.5MHz, then decimate both RX streams until they are the
> right rate to contain your tuned signals of interest but pass freely over
> USB2.0 bandwidth.
>
> It would be at least a days work for me to get that working well I
> suspect, and I'm very familiar with the FPGA code. Extrapolate your own
> milage accordingly. You should need very little new code, just a lot of
> shuffling of existing code, but you'll want a decent understanding of the
> workings of UHD and some verilog skills.
>
> -Ian
>
> On Apr 4, 2015, at 7:49 AM, Derek Murphy via USRP-users <
> usrp-users at lists.ettus.com> wrote:
>
> I've done a lot of google research and have not found a solution yet.
>
> I wanted to check and see if there is any way to use the B200 in 2 RX
> mode. I understand that you would not be able to TX at that time and the
> bandwidth on each RX channel would be lower than the full 56MB.
>
> The use case that I am trying to get working in GnuRadio to process two
> signals that are 45Mhz a part which wouldn't be terrible except the systems
> that I must use only have USB 2.0. If I could have the B200 use 2 RX each
> at low bandwidth that seems like it would work, the other option could be
> to have the B200 set to receive the full span of 45Mhz but filter out the
> unwanted regions and send back the much smaller result.
>
> Thanks
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