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

Sanjoy Basak sanjoybasak14 at gmail.com
Tue Jul 4 08:51:06 EDT 2017


Hi Derek,
I am using transmitter on continuous mode and then testing the phase of the
receivers with that python file. So, I am not retuning the transmitter
again. It's tuned once and then I am retuning the receiver and testing if
the phase is the same or different. So, with different retune the receivers
are having different offset phases at these frequencies.

I also tested with transmitter and receiver together, transmitting and
receiving at the same time and also tuning at the same time (with the
attached python file). However, I am getting the same result. The offset
phases is different at different retunes.

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 Tue, Jul 4, 2017 at 12:00 PM, Derek Kozel <derek.kozel at ettus.com> wrote:

> Hello Sanjoy,
>
> Your initial calls to set_center_freq are all correct and use the command
> time. However the other call to set_center_freq must also the
> set_command_time call.
>
> Regards,
> Derek
>
> On Tue, Jul 4, 2017 at 10:09 AM, Sanjoy Basak <sanjoybasak14 at gmail.com>
> wrote:
>
>> 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
>>
>>
>>
>>   <https://mailtrack.io/> Sent with Mailtrack
>> <https://mailtrack.io/install?source=signature&lang=en&referral=sanjoybasak14@gmail.com&idSignature=22>
>>
>> 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
>>>>
>>>>
>>>>
>>>>   <https://mailtrack.io/> Sent with Mailtrack
>>>> <https://mailtrack.io/install?source=signature&lang=en&referral=sanjoybasak14@gmail.com&idSignature=22>
>>>>
>>>> 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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