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

Derek Kozel derek.kozel at ettus.com
Tue Jul 4 09:52:07 EDT 2017


The transmitter will not have a meaningful phase value. You are comparing
the offsets between the four receivers. Looking at your cal_test4.py file
we can see that the set_f function tunes the transmitter and receivers and
does not use timed commands. This is also true for your receive only
cal_test_try.py. You will need to add timed commands to those so that all
four channels tune simultaneously.

    def set_f(self, f):
        self.f = f
        self.transmitter.set_center_freq(self.f, 0)
        self.transmitter.set_center_freq(self.f, 1)
        self.receiver.set_center_freq(self.f, 0)
        self.receiver.set_center_freq(self.f, 1)
        self.receiver.set_center_freq(self.f, 2)
        self.receiver.set_center_freq(self.f, 3)


On Tue, Jul 4, 2017 at 1:51 PM, Sanjoy Basak <sanjoybasak14 at gmail.com>
wrote:

> 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
>
>
>
>
>
>   <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 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
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>   <https://mailtrack.io/> Sent with Mailtrack
>>>>>>> <https://mailtrack.io/install?source=signature&lang=en&referral=sanjoybasak14@gmail.com&idSignature=22>
>>>>>>>
>>>>>>> _______________________________________________
>>>>>>> USRP-users mailing list
>>>>>>> USRP-users at lists.ettus.com
>>>>>>> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>>>>>>>
>>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>
>
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