On 11/11/2024 10:10, Marcus Müller wrote:
Hello!
Regarding what you see in trailing, my guess is that this is the step
response of the built-in DC offset cancellation filter; "DC offset
cancellation" is high-pass filter behaviour. This affects only
frequencies in your signal that are very low. It is meant to remove
imperfections that happen on every quadrature mixer&ADC device. So,
unless you really see a problem with the signal itself, this is
probably fine! You say you have an issue with this, but don't explain
the actual issue.
The phase in that trailing part can remain constant, that's OK. The
step response of a real-valued filter is real, and you should simply
see the phase of the last output sample at the moment of "input
switchoff".
Regarding "Amplitude and Signal length": I can't really tell what
you're showing us here. What kind of signal did you feed into the
USRP? Where does it come from? At which frequency? What is the USRP
tuned to? What's its sample rate? Most importantly: What is it that
worries you about this? As far as I can tell, this might seem normal,
and not an issue!
Best regards,
Marcus
What type of signal? Narrowband signals can be considerably more
affected by DC-offset correction than wideband
signals. One can use offset-tuning to move the signal outside the
"view" of the DC-offset correction. The second
argument to "tune_request" allows you to specify an offset.
Also, how are these devices connected? "Over the air" or with a cable.
If with a cable, please ensure that there's
adequate attenuation in the cable to prevent overload or even damage
to the B210 front-end.
On 11.11.24 14:18, yibinden...@outlook.com wrote:
Hi everyone,
I'm working on a project where I generate a signal and simultaneously
receive it using both the Pluto SDR and the USRP B210. However, I’m
running into some unexpected issues with the B210's reception, and
I’m hoping for some guidance.
Here are the main problems I’m encountering:
*Signal Trailing*: As shown in the figures, The signal received by
the Pluto has clear boundaries, while the signal received by the B210
has noticeable trailing compared to the Pluto.
*Strange Phase Characteristics*: The phase behavior of the
B210-received signal is unusual. Specifically，during the trailing
phase of the signal, the phase remains constant, which is unexpected.
When there is no signal, the phase appears to be chaotic.
*Amplitude and Signal Length*: As shown in the figure, when the
signal length is relatively short, both the maximum and the average
amplitude increase as the signal length grows.
I suspect that each sample might be significantly broadened in the
time domain, but since I am not entirely familiar with the USRP
B210's hardware processing, I am unsure if this is the root cause. I
am wondering if these issues could potentially be improved by
modifying the hardware configuration, such as adjusting the filter
settings or other parameters. The code I’m using for the B210
receiver is attached.
Has anyone experienced similar issues or have suggestions on
adjusting the B210's configuration or setup to address these
distortions? Any insights would be greatly appreciated.
Thanks in advance for your help!
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