[USRP-users] TX Image rejection B210

Marcus D. Leech mleech at ripnet.com
Mon Apr 13 09:24:04 EDT 2015


On 04/13/2015 05:50 AM, Sebastian Held via USRP-users wrote:
> Update:
>
> I played around with the LO offset feature and got the following result:
>
>
> The curves were generated by:
> blue: ./tx_waveforms --args="master_clock_rate=10e6" --rate 10000000 
> --freq=5900000000 --gain=50 --wave-type SINE --ref=gpsdo --int-n 
> --wave-freq=1000000 --lo_off=0
> green: ./tx_waveforms --args="master_clock_rate=10e6" --rate 10000000 
> --freq=5900000000 --gain=50 --wave-type SINE --ref=gpsdo --int-n 
> --wave-freq=1000000 --lo_off=2000000
> red: ./tx_waveforms --args="master_clock_rate=10e6" --rate 10000000 
> --freq=5900000000 --gain=50 --wave-type SINE --ref=gpsdo --int-n 
> --wave-freq=1000000 --lo_off=5000000
>
> Clearly visible: The wanted sine (-38.9 dBm) is offset 1 MHz from 5.9 
> GHz, which is correct.
> The LO is the signal at -69.2 dBm; it moves according to the LO offset 
> parameter.
> The to be rejected sideband is at -64.6 dBm.
>
> The specification of the B210 
> (http://www.ettus.com/content/files/b200-b210_spec_sheet.pdf) states:
> SSB/LO Suppression -35/50 dBc
>
> My measurement:
> SSB/LO Suppression -25.7/30.3 dBc
>
> This is far off.
> Does anyone have similar problems?
> Is there anything I can do to improve these figures?
>
> Sebastian
>
What version of UHD are you using?

Have you tried specifying a master clock rate that is a multiple of your 
(10Msps in your example) sample rate?


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