On 10/04/2023 14:28, Shenk, Trey E wrote:
I first tried turning the gain down. What I saw was that the even
harmonics (2*fundamental, …) did not change power, and the odd
harmonics decreased by the same amount as the fundamental. This means
that the dBc for the odd harmonics stayed the same with decreasing gain.
Decreasing the baseband amplitude had the exact same effect. Even
harmonics stayed at the same power level, odd harmonics decreased
while maintaining dBc.
What is the nature of the modulating signal?
If you use an example app like "tx_waveforms" with, let's say, 10kHz SIN
signal, what are the harmonic results?
*From:* Marcus D Leech <patchvonbr...@gmail.com>
*Sent:* Monday, April 10, 2023 8:39 AM
*To:* Shenk, Trey E <trey.sh...@pnnl.gov>
*Cc:* USRP-users@lists.ettus.com
*Subject:* Re: [USRP-users] Harmonic Distortion with B205mini
Check twice before you click! This email originated from outside PNNL.
Turn down the RF gain a bit as well as the baseband amplitude. Does
this make any difference?
Sent from my iPhone
On Apr 10, 2023, at 9:41 AM, Shenk, Trey E via USRP-users
<usrp-users@lists.ettus.com> wrote:
I'm using a B205mini to transmit signals. When transmitting, I can
see copies of the SOI at harmonics of the center frequency. I ran
some measurements of total harmonic distortion, and found it to
range from 39% with a 100MHz to 23% with a 1GHz carrier. The
second harmonic is <-50dBc, but the third harmonic is usually
around -10dBc.
My main concern is for the lower frequency carriers, like 100MHz,
because multiple harmonics will show up on a spectrum analyzer set
to a wideband. I've looked at putting an RF filter at the output,
but I need the system to be able to switch transmit center
frequencies in a range from 100MHz to 5GHz.
Is it possible to reduce the harmonics by some hardware setting
(driving with gnruadio)?
Thanks,
Trey
<carrier_freqsweep_fc0200M_gain55.png>
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