Hey Marcus,
I am using it to find the signal frequency present in the given band.
However, in
some cases, I found DC is more dominant, and I am unable to detect the
presence of
the signal and its frequency.
If I use the high pass filter to remove the DC offset, how should I
calculate the
cut-off? Considering the fact that there might be a signal at the center.
On Sun, Feb 11, 2024 at 10:52 PM Marcus Müller <marcus.mueller@ettus.com
<mailto:marcus.mueller@ettus.com>> wrote:
Hi Arhum,
some limited amount of DC offset is sadly to be expected from any direct
conversion architecture (that's a result of LO leakage as well as
systematic DC
offset).
Since DC is the lowest of all possible frequencies, a high-pass filter
can be
used to eliminate it. The design of that filter depends on what you
want to do
with the signal afterwards – for example, for some communication system
signals,
the DC offset literally doesn't matter.
Another option is, if your signal is sufficiently more narrowband than
the
Nyquist bandwidth dictated by your receiver's sampling rate, to
"offset-tune";
i.e., to put your signal of interest to the positive (or negative) side
of your
LO frequency, and then digitally shift the signal of interest to actual
baseband
and filter.
The USRPs bring that functionality out of the box, integrated into the
device's
digital part, so you can just deal with the signal decimated to the
bandwidth
you need in your computer. I'm not sure, but I don't think the HackRF
allows for
that. You'd have to offset-tune within your full sampling rate, and in
GNU Radio
use something like the "freq. X-lating FIR filter" to get the part of
the
spectrum you want.
Best regards,
Marcus
On 10.02.24 12:02, Arhum Ahmad wrote:
Hey all,
I'm currently working on frequency sensing using the HackRF SDR.
However, when
I calculate the FFT, I encounter a DC offset that's higher than the
actual
signal strength itself. This offset is interfering with my ability to
detect
the intended output accurately. Could you please assist me in
understanding how
to remove this DC offset?
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*Thanks and Regards**
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*Arhum Ahmad*
Ph.D. Scholar, Electrical Engineering Department, IIT Ropar
+91- <tel:+91-7015802356>7974897279 | arhum.19eez0005@iitrpr.ac.in
<mailto:2016eez0009@iitrpr.ac.in>
Lab No. 323, Communication Research Lab, J.C.Bose Building
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*Thanks and Regards**
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*Arhum Ahmad*
Ph.D. Scholar, Electrical Engineering Department, IIT Ropar
+91- <tel:+91-7015802356>7974897279 | arhum.19eez0005@iitrpr.ac.in
<mailto:2016eez0009@iitrpr.ac.in>
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