On 01/17/2019 01:22 AM, Koyel Das (Vehere) wrote:
Hi Marcus,
Thanks for the link.
1.In the link they are mentioning to issue time command when aligning
phase of multiple devices but is that required for a single device of
say 2955 R which has four receivers?
2.Further do all four receivers share a same master oscillator in 2955R?
Yes to both of those. If by "master oscillator" you mean the
reference clock used by the PLLs. Additionally, TwinRX cards (used in
the 2955)
allow actual LO sharing.
3.If I want to synchronize 2 or more 2955R do I need to use external
reference or it can be done without that?
You absolutely need a shared reference clock and 1PPS to synchronize
multiple 2955R units.
4.Will the synchronization done by using external reference be precise
enough for doing interferometry using multiple receivers?
Yes.
Regards,
Koyel
------------------------------------------------------------------------
*From:* USRP-users <usrp-users-boun...@lists.ettus.com> on behalf of
Marcus D. Leech via USRP-users <usrp-users@lists.ettus.com>
*Sent:* Wednesday, January 16, 2019 8:36:58 PM
*To:* usrp-users@lists.ettus.com
*Subject:* Re: [USRP-users] stability of USRP 2954R/2955R
On 01/16/2019 05:39 AM, Koyel Das (Vehere) via USRP-users wrote:
Hi,
Is the phase difference between two receiving channels in USRP 2954 R
or between any two channels of USRP 2955R stable? That is can I
measure the phase difference using a power splitter and equal length
cables and say that it will remain the same always or will it vary?
Regards,
Koyel
If you use timed commands to tune it:
https://files.ettus.com/manual/page_sync.html
You can get a reasonably predictable phase-offset. But since analog
effects (mostly temperature) will tend to change the fine-scale
phase, you should probably re-cal on every run, depending on your
tolerance for gross phase error.
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