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

Marcus D. Leech mleech at ripnet.com
Tue Dec 9 10:29:25 EST 2014


On 12/09/2014 07:53 AM, khalid.el-darymli wrote:
> Thanks very much for this information. According to the datasheet you 
> mentioned in the link below [1], the supported oscillating frequency 
> by CVHD-950 is 50 MHz to 130 MHz. The PN specs are provided for some 
> center frequencies in this range.
>
> However, I am interested in the HF band for which the LFTX/LFRX 
> support center frequencies up to 30 MHz. For requested center 
> frequencies in (DC, 30 MHz], do you digitally down-sample the center 
> frequency of CVHD-950? Is there any description on how exactly you do 
> that? and what effect does this may have on the phase noise of CVHD-950?
No, that is the reference clock for the entire platform--driving all 
timing in the platform, including the 100MHz sample clock for the ADCs. 
The schematics
   are here:

http://files.ettus.com/schematics/n200



>
> I am working on an ocean-based HF radar. Basically, the system 
> measures the Doppler frequency of ocean waves for different sea 
> states. It is important that I characterize my system to know its 
> limits and capabilities.
>
> Thanks for your help.
>
> Best,
> Khalid
>
> [1] http://www.crystek.com/home/oscillator/vcxodetail.aspx?pn=CVHD-950
>
> On Mon, Dec 8, 2014 at 7:35 PM, Matt Ettus <matt at ettus.com 
> <mailto:matt at ettus.com>> wrote:
>
>
>     With the LFRX and LFTX, there is no mixer, so all phase noise is
>     from the ADC clock.  The oscillator used is a CVHD-950 from
>     Crystek and you can find the phase noise spec for it on their web
>     site.
>
>     Matt
>
>     On Mon, Dec 8, 2014 at 2:11 PM, khalid.el-darymli via USRP-users
>     <usrp-users at lists.ettus.com <mailto:usrp-users at lists.ettus.com>>
>     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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>
>
>
>


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

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