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

Sanjoy Basak sanjoybasak14 at gmail.com
Tue Jul 4 05:09:54 EDT 2017


Hi Derek,
I am not using Rfnoc. The time and clock sources are set to external and
motherboard time is also set correctly. Please have a look in the code.

Right now I am using simple flowgraph and python codes to check the
calibration. Please have a look. I am not getting the repeated offset
phase. It is changing with every tuning.

Best regards
Sanjoy



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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 7:53 PM, Derek Kozel <derek.kozel at ettus.com> wrote:

> 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
>>
>>
>>
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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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>>>> _______________________________________________
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>>>>
>>>>
>>>
>>
>
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