This is what I see with a B210 at 145 MHz fundamental. I had the
analyzer on a large RBW, so the even order harmonic are buried in the
analyzer noise.
I don't think there's any remedy except for external filters.
Ron
B210 harmonics
On 4/12/23 16:20, Shenk, Trey E via USRP-users wrote:
The original signal that I showed was an unmodulated carrier.
I tried a 10kHz complex exponential (plots included for several
harmonics). The carrier is clearly visible at all frequencies. I can
see copies of the 10kHz tone on odd multiples of the carrier, but not
on the even multiples.
*From:* Marcus D. Leech <patchvonbr...@gmail.com>
*Sent:* Monday, April 10, 2023 10:22 PM
*To:* Shenk, Trey E <trey.sh...@pnnl.gov>
*Cc:* USRP-users@lists.ettus.com
*Subject:* Re: [USRP-users] Harmonic Distortion with B205mini
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>
<mailto:patchvonbr...@gmail.com>
*Sent:* Monday, April 10, 2023 8:39 AM
*To:* Shenk, Trey E <trey.sh...@pnnl.gov> <mailto: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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