[USRP-users] Phase Noise for USRP N200 with LFTX/LFRX

Marcus D. Leech mleech at ripnet.com
Mon Dec 8 17:21:48 EST 2014


On 12/08/2014 05:11 PM, khalid.el-darymli via USRP-users wrote:
> Hi,
>
> According to the specs provided in [1], the RF performance of USRP 
> N200/N201 is characterized for the WBX daughter-board. Particularly, 
> phase noise measurements are given for three offsets from a center 
> frequency of 1.8 GHz.
>
> My question is, are there any such measurements for the LFTX/LFRX 
> daughter-board?
>
> If not, is there a recommended procedure for doing these measurements?
> Among others, I am particularly concerned with the phase noise and its 
> short-term effect on my Doppler measurements.
>
>
> [1] 
> https://www.ettus.com/content/files/07495_Ettus_N200-210_DS_Flyer_HR_1.pdf
>
> Thanks,
> Khalid
>
>
>
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> USRP-users at lists.ettus.com
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Phase-noise on non-down/up-converting cards is utterly-dominated by the 
phase-noise of the system master clock, which on the N200 is
   a good-quality TCXO with low phase noise.  I don't have the 
part-number off the top of my head, but one of the Ettus hardware folks
   can point you (and the rest of the assembled multitude here) to the 
part number, and consequent datasheet.


That can always be improved by using an external clock with lower phase 
noise, where you can improve it in a manner that scales non-linearly
   with $$ spent, typically.

Articles like this can help with measurement technique:

http://www.radio-electronics.com/info/t_and_m/spectrum_analyser/measuring-phase-noise-measurements.php

My suspicion is that unless you're trying to measure very-fine-scale 
distances and/or motion, that phase-noise shouldn't be of major concern.




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