Dear Fikrat,
Feed in a known power, note down the digital power, repeat for another
known power.
You'll get three input power->digital power mappings.
Now, assume the power transfer function is a linear one:
$P_{digital} = G\cdot P_{analog} + P_{noise}$
With the two $(P_{digital}, P_{analog})$ measurements you can simply
deduce the slope $G$ of the above function; simple math, subtract the
equations:
$P_{digital,1}-P_{digital,2}=(G\cdot P_{analog,1} + P_{noise})-(G\cdot
P_{analog,2} + P_{noise})=G(P_{analog,1}-P_{analog,2})$
and find $G$ and the offset $P_{noise}$.
Repeat with a few other known powers to make sure you're in the linear
region.
Whatever you do, never feed in more than -15dBm into your device!
Best regards,
Marcus
On 21.03.2016 23:05, Fikrat Al-Kazimi wrote:
> Hi guys,
>
> I hope you're all doing well.
>
> I'm been searching a lot and I read that if I want to measure the
> absolute power ( in W or dBm ) using the usrp_spectrum_sense.py, then
> I must calibrate the USRP by injecting a signal of known physical power.
>
> Can someone please walk me through the calibration steps? How can I
> accomplish this and what do I edit in the code after calibration is
> complete to help me sense the absolute power instead of power_dB?
>
> Thank you for your help!
>
>
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