[USRP-users] phase-aligning two USRPs without Octoclock

Sourin Mondal (Vehere) sourin.mondal at vehere.com
Tue Jan 28 05:30:17 EST 2020


________________________________
From: Marcus D. Leech <patchvonbraun at gmail.com>
Sent: Monday, January 27, 2020 11:54 AM
To: Sourin Mondal (Vehere) <sourin.mondal at vehere.com>
Cc: usrp-users at lists.ettus.com <usrp-users at lists.ettus.com>
Subject: Re: [USRP-users] phase-aligning two USRPs without Octoclock

On 01/27/2020 01:00 AM, Sourin Mondal (Vehere) wrote:
Hi Marcus,

Thanks for the information. Could you please also tell what is the accuracy with which the phases are aligned between USRP channels, when we use 10 MHz reference to align, in pico-seconds or nano-seconds?

Regards,
Sourin
The answer to that question depends very much on the hardware involved.

In general, two synthesizers locked to the same clock won't have a zero phase *offset* from one another, but will be phase-coherent
  on an ongoing basis.

Now, for *some* types of Ettus hardware, there is special hardware that can arrange to phase-reset during tuning, so that all the participating
  synthesizers will have small phase-offsets with respect to one another.

We generally talk in terms of degrees, rather than picoseconds or nanoseconds.  Residual phase offsets will typically be under 5 degrees.

But keep in mind that things like differential heating of cables, and internal circuit in ANY coherent radio can case the phase relationships
  to drift slightly.




________________________________
From: Marcus D. Leech <patchvonbraun at gmail.com><mailto:patchvonbraun at gmail.com>
Sent: Thursday, January 23, 2020 12:48 PM
To: Sourin Mondal (Vehere) <sourin.mondal at vehere.com><mailto:sourin.mondal at vehere.com>
Subject: Re: [USRP-users] phase-aligning two USRPs without Octoclock

On 01/22/2020 11:53 PM, Sourin Mondal (Vehere) wrote:

Hi Marcus,
Do I need to use 1 PPS also along with 10 MHz reference? And are there any software commands to be used along with these hardware configuration for synchronizing multiple USRPs without octoclock? If so what are those commands?

Regards,
Sourin
You would do well to spend some time with this app-note:

https://kb.ettus.com/Synchronization_and_MIMO_Capability_with_USRP_Devices

Indeed, there are many app-notes that might be relevant for you.

Along with:

http://files.ettus.com/manual/



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