[USRP-users] TX Image rejection B210

Sebastian Held sebastian.held at imst.de
Mon Apr 13 05:50:00 EDT 2015


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


Am 07.04.2015 um 09:47 schrieb Sebastian Held via USRP-users:
> Hi,
>
> Any news on this?
> I have the same problem with two B210 units.
> Either the error is my misunderstanding of RF performance parameters,
> the example file cannot be used for this performance evaluation or the
> hardware design does not meet the performance of the AD chip (which is
> hard to believe).
>
> Any hint what I'm doing wrong?
>
> Regards,
> Sebastian
>
> Am 31.03.2015 um 09:51 schrieb Sebastian Held via USRP-users:
>> forgot to include the list.
>>
>> Dear Martin,
>>
>> please see attached figure. Reducing the gain acts on both the wanted
>> and unwanted signal in the same manner.
>>
>> Sebastian
>>
>> Am 30.03.2015 um 18:46 schrieb Martin Braun via USRP-users:
>>> Sebastian,
>>>
>>> what happens when you turn down the gain (e.g. to 70 dB)?
>>>
>>> M
>>>
>>> On 29.03.2015 23:50, Sebastian Held via USRP-users wrote:
>>>> Hi,
>>>>
>>>> I'm currently investigating a problem with my OFDM modulated signals. To
>>>> understand, why the spectrum mask is violated, I first checked the basic
>>>> TX parameters. The B210 is connected to a R&S FSQ26 via a 20 dB
>>>> attenuator.
>>>>
>>>> I use the examples provided with the
>>>> UHD-release_003_008_002-10-ge067c45:
>>>> ./tx_waveforms --args="master_clock_rate=20e6" --rate 20000000
>>>> --freq=5900000000 --gain=80 --wave-type SINE --ref=gpsdo --int-n
>>>> --wave-freq=1000000
>>>>
>>>> This command results in an expected tone at 5.9 GHz + 1 MHz (approx. -29
>>>> dBm) and its image at 5.9 GHz - 1 MHz. The problem is: the image power
>>>> is very large: only 26 dB below the wanted 5.901 GHz tone. From the
>>>> AD9361 data sheet I would expect a suppression of at least 45 dB.
>>>>
>>>> To continue to solve my original problem (OFDM spectrum) I first need to
>>>> understand, why I get such a large image.
>>>> Can I use this example to evaluate the TX image? Any pointers?
>>>>
>>>> Regards,
>>>> Sebastian
>>>>
>>>>
>>>>
>>>> _______________________________________________
>>>> USRP-users mailing list
>>>> USRP-users at lists.ettus.com
>>>> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>>>>
>>> _______________________________________________
>>> USRP-users mailing list
>>> USRP-users at lists.ettus.com
>>> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>>>
>>
>>
>> _______________________________________________
>> USRP-users mailing list
>> USRP-users at lists.ettus.com
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>
> -- 
> Sebastian Held (Dipl.-Ing.)
> IMST GmbH
> Software Engineer
>
>
> _______________________________________________
> USRP-users mailing list
> USRP-users at lists.ettus.com
> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com

-- 
Sebastian Held (Dipl.-Ing.)
IMST GmbH
Software Engineer
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