[USRP-users] Sequence Errors on USRP N200

Jahshan Bhatti jabhatti91 at gmail.com
Tue Jun 26 11:07:06 EDT 2012


On Sun, Jun 24, 2012 at 8:26 PM, Jahshan Bhatti <jabhatti91 at gmail.com> wrote:
>
> Ok, instead of using the timing receivers, I simply cross-correlated
> the signals with a MIMO set of USRP N200s. From the cross-correlation,
> I can see that the delay is stable on multiple runs but not exact.
> Here are my results:
>
> command 50 ms delay @ 5 MS/s results in error of -5.75 us
> command 50 ms delay @ 4 MS/s results in error of -4.75 us
> command 100 ms delay @ 5 MS/s results in error of -5.75 us
> command 100 ms delay @ 4 MS/s results in error of -4.75 us
> command 200 ms delay @ 5 MS/s results in error of 121.75 us
> command 200 ms delay @ 4 MS/s results in error of 154.5 us
>

Does anyone know what the delays in digitization and generation are in
the USRP N200? I bet the constant microsecond delays at 50 and 100 ms
are due to samples getting shifted in and out of buffers in the FPGA,
ADC, and DAC hardware. It would be nice to have an explanation for
these delays so that way I can safely calibrate them out.

~Jahshan




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