[USRP-users] Frequency resolution of UBX-160 with integer N mode

Fabian Schwartau fabian at opencode.eu
Mon Mar 4 11:38:42 EST 2019


Hi,

please double check on that, as I am not 100% sure.
As far as I was able to figure out, the LO is generated from the 
Daughterboard internal 200 MHz reference (which is dirived from the 10 
MHz), but is divided by 4 for some reason, so you get multiples of 50 
MHz. This will also induce a random 90° phase shift between the signals, 
which is a big problem for MIMO stuff.
At least the TwinRX boards we used were able to share the LO between 
multiple channels, which fixed the problem for us.

Best regards,
Fabian

Am 04.03.2019 um 17:23 schrieb Andreas Leuenberger via USRP-users:
> Hello all,
> 
> I am using a USRP X310 with two daughter boards UBX-160 v2. To get a 
> stable phase difference of the two daughter boards, I use the RX LOs in 
> integer N mode ("mode_n=integer"). - I have noticed that the frequency 
> step of the LO is 50 MHz. As the frequency of the reference signal is 10 
> MHz, I would expect a step of 10 MHz.
> 
> Is there a way to reduce this frequency step?
> 
> Thanks for your help,
> andreas
> 
> 
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