[USRP-users] TwinRx transfert function

Olivier Ravard olivier.ravard at novagrid.com
Wed Nov 6 12:28:54 EST 2019


1. The tune frequency is 1200 MHz in this case but we obtain same order of magnitude
for fluctuations if another frequency is tuned (but transfert function could be different).
Our tests includes L band acquisitions (950 - 2150 MHz).

2. The gain in this case is set in order to have 15 dB backoff (which is margin relative
to the
maximum ADC amplitude). In this case, we use 85dB gain because the noise generator gives
a level around -135 dBm/Hz. But we observed the same things when we sample satellite
signals using 65dB gain.

3. what do you mean by "overruns".

regards,

Olivier 

Le 06/11/2019 à 17:59, Marcus D Leech a écrit :
> That is more passband ripple than I would expect. 
>
> What is your tunes frequency. What gain setting? Are you getting overruns during the
> measurement?
>
>
> Sent from my iPhone
>
>> On Nov 6, 2019, at 6:32 AM, Olivier Ravard via USRP-users <usrp-users at lists.ettus.com>
>> wrote:
>>
>> 
>>
>> Hello,
>>
>> We use X300 with 2 TwinRx boards for acquisitions in L band (UHD 3.10.3).
>>
>> It seems that the transfert function of the couple (X300 - TwinRx) shows strong
>> fluctuations.
>> To measure these fluctuations, we put a white noise generator at the input (this
>> generator was
>> measured before with a spectrum analyser and it show a very flat transfert function
>> over 1 GHz)
>> and we measure the PSD of the sampled 80MHz bw signal for the 4 inputs.
>>
>> The result is shown on figures below:
>>
>> inputs 1 and 2 (first TwinRx):
>>
>> <bbhnehmblikapiem.png>
>> <fpnpgddncnklhkma.png>
>>
>> inputs 3 and 4 (second TwinRx):
>>
>> <lfkojlkpiadfgnml.png>
>> <bnokbonaahldkokn.png>
>>
>> Are these fluctuations normal ?
>>
>> regards,
>>
>> -- 
>> Olivier
>> _______________________________________________
>> USRP-users mailing list
>> USRP-users at lists.ettus.com
>> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com

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