Re: Receive amplitude consistency

[Mike]

Marcus,

Thank you for your response.

The variation is on the order of 20%, although it changes from run to run.

Power level from the generator is 10 mV through 40 dB of attenuation.

The B200 is set for maximum gain (minimum attenuation) and is using sc8
format with peak=0.1.


Thanks!


On 4/21/2021 10:42 AM, Marcus D Leech wrote:
> What is the magnitude of the inconsistency?
>
> If you replace the signal generator with a 50 ohm terminator and increase the 
> gain to near maximum, do you still see the inconsistency?
>
> What power level are you injecting from the signal generator. 
>
> Sent from my iPhone
>
>> On Apr 21, 2021, at 12:27 AM, Mike <mike.nelson@rdss.com> wrote:
>>
>> Hello,
>>
>> I'm hoping someone can shed some light on an apparent inconsistency
>> issue I'm seeing with received I/Q amplitude.
>>
>> I have a B200 directly connected to an arbitrary waveform generator
>> through an attenuator.  The generator is programmed to repeatedly send a
>> fixed sequence of AM pulses at a set power level.  On the host (Ubuntu
>> 20.04, UHD 3.15.0), a C++ program simply gathers samples (48 MSPS, sc8
>> OTW and CPU) and computes the average amplitude as I^2 + Q^2.
>>
>> During a run of the host software, the reported amplitudes are
>> consistent from sequence to sequence.
>>
>> However, if the host software is stopped and immediately restarted,
>> without changing the generator, the reported amplitudes are again
>> consistent but at a different level than the previous invocation.
>>
>> Is there some internal adjustment or variable setting performed during
>> USRP creation and setup that would cause the received I/Q sample
>> amplitudes to vary with each startup?
>>
>>
>> Thanks!
>>
>>
>>