[USRP-users] Phase Noise for USRP N200 with

Marcus D. Leech mleech at ripnet.com
Tue Dec 9 13:01:54 EST 2014


On 12/09/2014 12:52 PM, Louis Brown via USRP-users wrote:
> When I was doing FMCW RADAR for wave measurements I'd use delay lines for calibration.  If you are using the LFTX for transmit then the ADC and DAC jitter (due to common clock) will be correlated.  If you loop the TX back to RX via a long delay line the phase noise spectrum should be a high pass function; essentially the noise gets worse with target range.  This is really no different than the delay line method of phase noise measurement.
> Lou
>
Also, if you need better phase noise than the N200 delivers standalone, 
then an external 10Mhz reference (GPSDO, OCXO, Rb oscillator, etc) can be
   used to reduce phase-noise.

I don't know that much about the original NOAA CODAR installations--did 
they use very-low-phase-noise clock designs?





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