[USRP-users] LFTX output amplitude (Michael Rahaim)

Michael Rahaim mrahaim at bu.edu
Thu Dec 11 10:53:05 EST 2014

Thanks Lou. I think I get what you're saying, but the end result seems to
end up as a channel gain as opposed to a DC offset. For example, if I set
my signal so that it initializes to a sine wave with peak to peak amplitude
of 1V, after turning the carrier on and off it might end up having a pk-pk
amplitude of 0.5V or 0.2V or 0.8V.

Is there a way to reset via software such that the accumulator gets set
back to 0?

Thanks again,


On Thu, Dec 11, 2014 at 9:08 AM, Louis Brown <rfengr00 at me.com> wrote:

> Ok what you are describing is the phase accumulator halting to a non zero
> state when you tune the oscillator back to 0 Hz.  Try generating a very low
> frequency sine wave (a few Hz) and you see what I mean when you tune it
> away from 0 Hz and then return it.  When you start you flow with a 0 Hz
> source, the accumulator is initialized to zero, then it starts accumulating
> when you tune it to some frequency.  Return it to 0 Hz and it stops at a
> non-zero phase, which is equivalent to a DC offset.  I'm sure this is the
> way it is supposed to work, and is what I have observed before.
> Lou
> On Dec 11, 2014, at 07:21, Michael Rahaim <mrahaim at bu.edu> wrote:
> Hi Lou,
> I have the output of the LFTX connected to a scope. I'm not using the LFRX
> in the test loop.
> Best,
> -Mike
> On Wed, Dec 10, 2014 at 7:44 PM, Louis Brown via USRP-users <
> usrp-users at lists.ettus.com> wrote:
>> How are you measuring the LFTX output?  With additional test equipment or
>> looping it back into the LFRX?
>> Lou
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>> USRP-users at lists.ettus.com
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