[USRP-users] calibration on Wifi bands for X310/UBX

Derek Kozel derek.kozel at ettus.com
Mon Jul 3 13:53:27 EDT 2017


Hi Sanjoy,

Timed commands will definitely be required in order to have repeatable
phase offsets. To check, you are (re)setting the time on each X310 at the
start of your program and have set the clock and time sources to external?

Are you using the multi_usrp API and creating a single rx_streamer with all
four channels? If you are using the RFNoC API then timed commands must be
used to set the DDC frequency (if non-zero) as well since that has an
effect on the phase which is stateful.

Can you please paste your code for setting the rx frequency? Also for
setting the motherboard time?

Thank you,
Derek

On Mon, Jul 3, 2017 at 6:20 PM, Sanjoy Basak <sanjoybasak14 at gmail.com>
wrote:

> Hi Derek,
> I am referreing to phase calibration. I am taking one transmit signal
> (sine/cosine wave) from one x310 and distributing the signal through a 1x4
> power divider and feeding it to 4 receivers of 2 other X310s. All the X310s
> are connected to the octoclock. Afterwards I am comparing the phase of 4 RX
> signals.
>
> For calibration, I take one rx signal as the reference signal and find the
> phase differences of other 3 rx signals compared to the reference signal. I
> save the offset (initial) phases and use it further for calibration.
>
> As I mentioned earlier, for 2.4 GHz, 2.45 GHz and 2.5 Ghz, I find the
> phase calibration remains even after restarting (or retuning) the USRP.
> However, for other Wifi bands (for example 2412 MHz or 2452 MHz ...) the
> phase calibration does not remain. After retuning, I find the calibration
> is gone.
>
> I also used set_command_time method. But the result was the same.
>
> Best regards
> Sanjoy
>
>
>
>   <https://mailtrack.io/> Sent with Mailtrack
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>
> Sanjoy Basak
> Researcher
> Royal Military Academy
> Dept. Communication, Information Systems & Sensors (CISS)
> 30, Avenue de la Renaissance
> B-1000 Brussels
> BELGIUM
> Tel : +32-2441 4162
> email: Sanjoy.BASAK at mil.be
>
> On Mon, Jul 3, 2017 at 6:29 PM, Derek Kozel <derek.kozel at ettus.com> wrote:
>
>> Hello Sanjoy,
>>
>> What calibration are you referring to? Frequency, amplitude, phase? How
>> are you doing your calibration and how are you checking it? The more you
>> can tell us about your method and the results you are seeing the better we
>> can answer.
>>
>> Regards,
>> Derek
>>
>> On Mon, Jul 3, 2017 at 4:46 PM, Sanjoy Basak via USRP-users <
>> usrp-users at lists.ettus.com> wrote:
>>
>>>
>>> Hello Experts,
>>> I am trying to calibrate X310/UBX on the whole wifi bands (the complete
>>> 2.4 GHz band).
>>> 2.412,2.417,2.422,....,2.484 GHz
>>>
>>> I am doing direction finding tests and need to calibrate 4 channels of 2
>>> X310s on the specified frequencies. Both X310s are connected with
>>> Octoclock. However, I could only have calibration on 2.4 GHz, 2.45 GHz, 2.5
>>> GHz. For other bands, calibration does not remain after retuning. Is there
>>> any specific reason why the calibration only works for every 50 Mhz channel
>>> after retuning. I tested with different sampling rates, but the result is
>>> the same. Calibration does not remain after retuning.
>>>
>>> I am using UHD_003.009.002 (installed from synaptic) and ubuntu 16.04.
>>> Is there any specific way how I can make it work?
>>>
>>> Best regards
>>> Sanjoy Basak
>>>
>>>
>>>
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>>>
>>> _______________________________________________
>>> USRP-users mailing list
>>> USRP-users at lists.ettus.com
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>>>
>>>
>>
>
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