[USRP-users] Phase coherence problems using TVRX2

Lucas Caldeira de Oliveira lucasktr at gmail.com
Wed Jun 13 14:06:43 EDT 2012


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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