[USRP-users] different phase difference using splitter on each run

Marcus D. Leech patchvonbraun at gmail.com
Tue Mar 5 22:36:24 EST 2019


On 03/05/2019 10:28 PM, Koyel Das (Vehere) wrote:
>
> "I'm not familiar with the 2964R, so can't personally comment on it."
>
>
> Sorry I meant 2954 R. Does it also have LO sharing or that is not 
> required in that?
>
>
> Regards,
>
That model is based on the UBX transceiver card, which doesn't have LO 
sharing, but using timed commands can cause the two
   synthesizers to come into phase alignment.


>
> Koyel Das
> Senior – Product Engineer
>
> Vehere | Proactive Communications Intelligence & Cyber Defence
> M: +919051132173 | T: +91 33 40545454 | F: +91 33 40545455 | W: 
> www.vehere.com <http://www.vehere.com/>/
> /
> /unnamed 
> <https://www.linkedin.com/company/vehere-interactive-p-ltd>unnamed (1) 
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>
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> ------------------------------------------------------------------------
> *From:* Marcus D. Leech <patchvonbraun at gmail.com>
> *Sent:* Tuesday, March 5, 2019 9:57 PM
> *To:* Koyel Das (Vehere); 'USRP-users at lists.ettus.com'
> *Subject:* Re: [USRP-users] different phase difference using splitter 
> on each run
> On 03/05/2019 11:21 AM, Koyel Das (Vehere) wrote:
>> So they don’t share same master oscillator? Is this true for 2964R as 
>> well?
> Do you mean the reference clock on the board?  They all share that, 
> but each channel has its own LO synthesizer.
>
> I'm not familiar with the 2964R, so can't personally comment on it.
>
> You can achieve 4-channel phase coherence with the TwinRx--see the APP 
> Note here:
>
> https://kb.ettus.com/Direction_Finding_with_the_USRP%E2%84%A2_X-Series_and_TwinRX%E2%84%A2
>
>>
>> Koyel Das
>> Senior – Product Engineer
>> Vehere | Proactive Communications Intelligence & Cyber Defence
>> M: +919051132173 | T: +91 33 40545454 | F: +91 33 40545455 | W: 
>> www.vehere.com <http://www.vehere.com>
>>
>>
>>
>> Vehere is the proud recipient of the Fastest Growing Technology 
>> Company Awards in India & Asia since 2012!
>>
>> The content of this e-mail is confidential and intended solely for 
>> the use of the addressee. The text of this email (including any 
>> attachments) may contain information, which is proprietary and/or 
>> confidential or privileged in nature belonging to Vehere Interactive 
>> Pvt Ltd and/or its associates/ group companies/ subsidiaries. If you 
>> are not the addressee, or the person responsible for delivering it to 
>> the addressee, any disclosure, copying, distribution or any action 
>> taken or omitted to be taken in reliance on it is prohibited and may 
>> be unlawful. If you have received this e-mail in error, please notify 
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>> The recipient acknowledges that no guarantee or any warranty is given 
>> as to completeness and accuracy of the content of the email. The 
>> recipient further acknowledges that the views contained in the email 
>> message are those of the sender and may not necessarily reflect those 
>> of Vehere Interactive Pvt Ltd. Before opening and accessing the 
>> attachment please check and scan for virus. WARNING: Computer viruses 
>> can be transmitted via email. The recipient should check this email 
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>> no liability for any damage caused by any virus transmitted by this 
>> email.
>> ------------------------------------------------------------------------
>> *From:* Marcus D. Leech <patchvonbraun at gmail.com> 
>> <mailto:patchvonbraun at gmail.com>
>> *Sent:* Tuesday, March 5, 2019 9:49:28 PM
>> *To:* Koyel Das (Vehere); 'USRP-users at lists.ettus.com 
>> <mailto:USRP-users at lists.ettus.com>'
>> *Subject:* Re: [USRP-users] different phase difference using splitter 
>> on each run
>> On 03/05/2019 11:10 AM, Koyel Das (Vehere) wrote:
>>> Are RX1 and RX2 of RF0 controlled by same master oscillator? Will 
>>> connecting two antennas to RX1 and RX2 of RF0, rather than to RX1 of 
>>> RF0 and to RX1 of RF1, give same phase difference between these two 
>>> channels at every run?
>> All channels have their own LO.
>>
>> The TwinRx has LO sharing mode.
>>
>>
>>>
>>> Koyel Das
>>> Senior – Product Engineer
>>> Vehere | Proactive Communications Intelligence & Cyber Defence
>>> M: +919051132173 | T: +91 33 40545454 | F: +91 33 40545455 | W: 
>>> www.vehere.com <http://www.vehere.com>
>>>
>>>
>>>
>>> Vehere is the proud recipient of the Fastest Growing Technology 
>>> Company Awards in India & Asia since 2012!
>>>
>>> The content of this e-mail is confidential and intended solely for 
>>> the use of the addressee. The text of this email (including any 
>>> attachments) may contain information, which is proprietary and/or 
>>> confidential or privileged in nature belonging to Vehere Interactive 
>>> Pvt Ltd and/or its associates/ group companies/ subsidiaries. If you 
>>> are not the addressee, or the person responsible for delivering it 
>>> to the addressee, any disclosure, copying, distribution or any 
>>> action taken or omitted to be taken in reliance on it is prohibited 
>>> and may be unlawful. If you have received this e-mail in error, 
>>> please notify the sender and remove this communication entirely from 
>>> your system. The recipient acknowledges that no guarantee or any 
>>> warranty is given as to completeness and accuracy of the content of 
>>> the email. The recipient further acknowledges that the views 
>>> contained in the email message are those of the sender and may not 
>>> necessarily reflect those of Vehere Interactive Pvt Ltd. Before 
>>> opening and accessing the attachment please check and scan for 
>>> virus. WARNING: Computer viruses can be transmitted via email. The 
>>> recipient should check this email and any attachments for the 
>>> presence of viruses. The company accepts no liability for any damage 
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>>> ------------------------------------------------------------------------
>>> *From:* USRP-users <usrp-users-bounces at lists.ettus.com> 
>>> <mailto:usrp-users-bounces at lists.ettus.com> on behalf of Marcus D. 
>>> Leech via USRP-users <usrp-users at lists.ettus.com> 
>>> <mailto:usrp-users at lists.ettus.com>
>>> *Sent:* Tuesday, March 5, 2019 7:03:42 PM
>>> *To:* usrp-users at lists.ettus.com <mailto:usrp-users at lists.ettus.com>
>>> *Subject:* Re: [USRP-users] different phase difference using 
>>> splitter on each run
>>> On 03/05/2019 06:01 AM, Koyel Das (Vehere) via USRP-users wrote:
>>>>
>>>> Hi,
>>>>
>>>>
>>>> I am using USRP 2955 R and I have connected an antenna to one end 
>>>> of a two channel splitter and connected the other two ports of the 
>>>> splitter to the two RX1 pors of USRP. I am getting different phase 
>>>> difference in each run of USRP though in one particular run the 
>>>> phase difference is constant for all channels. The tuned frequency 
>>>> is 2.4 GHz and sampling rate is 1 MSps so as expected that channel 
>>>> phase differences are almost same. But when I stop acquiring data 
>>>> and restart it using gnuradio or the API, then I am getting again a 
>>>> new value of phase difference across all channels, which is again 
>>>> same across channels. Is USRP so unstable that it gives different 
>>>> value of phase difference for each run for the same frequency, and 
>>>> sampling rate? The setup in the runs are also the same.
>>>>
>>>>
>>>> Regards,
>>>>
>>>> Koyel
>>>>
>>>>
>>>> Koyel Das
>>>> Senior – Product Engineer
>>>>
>>>> Vehere | Proactive Communications Intelligence & Cyber Defence
>>>> M: +919051132173 | T: +91 33 40545454 | F: +91 33 40545455 | W: 
>>>> www.vehere.com <http://www.vehere.com/>/
>>>> /
>>> /
>>> /This isn't about "instability".  It's about the way PLL 
>>> synthesizers work, and the fact that by default each channel is 
>>> using its own synthesizer.
>>>
>>> There are a few things that need to happen:
>>>
>>>    All the channels you're receiving need to be in the same 
>>> multi_usrp block, which, among other things, is a conceptual 
>>> "synchronization domain".
>>>
>>>    Use timed-commands for tuning (which is a bit awkward to arrange 
>>> in Gnu Radio, you'll have to modify the generated code).  This will 
>>> arrange
>>>    for the synthesizers to be given a "resynch" signal at exactly 
>>> the same time.
>>>
>>>    OR
>>>
>>>    Use the "shared LO" features of the TwinRX cards that are on the 
>>> 2955.
>>>
>>> See the knowledge-base document on the TwinRX and 
>>> phase-synchronization here:
>>>
>>> https://kb.ettus.com/TwinRX
>>>
>>>
>>>
>>>
>>>
>>>>
>>>> /unnamed 
>>>> <https://www.linkedin.com/company/vehere-interactive-p-ltd>unnamed 
>>>> (1) <https://twitter.com/VehereIndia>unnamed (2) 
>>>> <https://www.facebook.com/VehereIndia/>
>>>>
>>>> Vehere is the proud recipient of the Fastest Growing Technology 
>>>> Company Awards in India & Asia since 2012!/
>>>>
>>>> The content of this e-mail is confidential and intended solely for 
>>>> the use of the addressee. The text of this email (including any 
>>>> attachments) may contain information, which is proprietary and/or 
>>>> confidential or privileged in nature belonging to Vehere 
>>>> Interactive Pvt Ltd and/or its associates/ group companies/ 
>>>> subsidiaries. If you are not the addressee, or the person 
>>>> responsible for delivering it to the addressee, any disclosure, 
>>>> copying, distribution or any action taken or omitted to be taken in 
>>>> reliance on it is prohibited and may be unlawful. If you have 
>>>> received this e-mail in error, please notify the sender and remove 
>>>> this communication entirely from your system. The recipient 
>>>> acknowledges that no guarantee or any warranty is given as to 
>>>> completeness and accuracy of the content of the email. The 
>>>> recipient further acknowledges that the views contained in the 
>>>> email message are those of the sender and may not necessarily 
>>>> reflect those of Vehere Interactive Pvt Ltd. Before opening and 
>>>> accessing the attachment please check and scan for virus. WARNING: 
>>>> Computer viruses can be transmitted via email. The recipient should 
>>>> check this email and any attachments for the presence of viruses. 
>>>> The company accepts no liability for any damage caused by any virus 
>>>> transmitted by this email.
>>>>
>>>
>>
>

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