[USRP-users] Phase coherence problems using TVRX2

Lucas Caldeira de Oliveira lucasktr at gmail.com
Thu Jun 14 13:31:38 EDT 2012


Thanks for the answers. I sent this document to my project team.

Lucas

2012/6/14 John Malsbury <john.malsbury at ettus.com>

> **
> Lukas,
>
> I forgot to mention that we do have a new knowledge base up.  There is a
> document you'll find there that explains the requirements for a MIMO system
> that can be used for direction of arrival measurements.
>
> I recommend taking a look: www.ettus.com/kb
>
> Search "MIMO" if you can't find the document in the menus.
>
> Cheers,
> John Malsbury
>
>
>
>
> On 06/13/2012 11:06 AM, Lucas Caldeira de Oliveira wrote:
>
> Hi,
>
> I'm working on a project that uses a linear array with four antennas for
> direction of arrival measurement. In this scenario, phase-coherency between
> each antenna is necessary.
>
> I'm using one USRP rev4.5 with two TVRX2 rev1.1. I found that a random
> phase offset is occuring every time i execute the program. After LO lock,
> the phase offset remains constant.
>
> Inside FPGA, the phase accumulator is the same for four DDCs. These
> signals between the input of ADC and inside GNURadio are phase coherent.
> This random phase offset is occuring inside TVRX2.
>
> I'm using the last version of UHD and GNURadio.
>
> Could you give us information about this problem? Is it possible to
> achieve phase coherency between these signals? Is there any limitation in
> TVRX2 about this?
>
> Thanks,
>
> Lucas
>
>
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