Re: [Discuss-gnuradio] How to ensure 2 USRP to have the same internal FPGA configuration when measuring the same signal?

[Marcus D. Leech]

On 01/23/2013 03:16 AM, LD Zhang wrote:

Hi Folks,

 

I have managed to use 2 different USRP N210’s to measure the same signal with the same sampling rate (both center at 0 Hz DC) at approximately the same time (timing is an issue but irrelevant for this discussion). Examination of signal intensity does confirm the above to be true. However, when I compare individual tones between the 2 units, I see the phase differences between the tones jump around a lot. And they seem to cluster at +90/-90 locations.

 

This is very puzzling and troublesome. I guess internally the USRP configures the FPGA in a way that is not visible. Is there a way that I con force the 2 USRP to configure the FPGA in the same identical configuration when taking data?

 

Thanks for your inputs and help.

 

LD

You aren't synchronizing the two N210s with an external clock reference, so there's no way there'll be phase coherence between the two devices.

-- 
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org