Re: Receive amplitude consistency

[Marcus D Leech]

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!
> 
> 
>