Problem about the value of spectrum_sense's power

Hi,all
i have been studied usrp_spectrum_sense for a while and acquired some
achievements of spectrum sensing. But there is still a problem confused
me,that is the value of my output power spectrum. i use bluetooth signal
as my source signal because of its frequency range. i also look up the
specification of this bluetooth signal’s power, it’s about 20dBm.
However, my received signal from usrp value is large more than 20dBm,
it’s about 70dBm. i do not know what should i modify from
spectrum_sense.py. Is it the gain control cause? i am now in trouble,any
help would be appreciate.

Regards

On Mon, 2011-03-28 at 09:23 +0800, george1012 wrote:

Hi,all
i have been studied usrp_spectrum_sense for a while and acquired some
achievements of spectrum sensing. But there is still a problem confused me,that is
the value of my output power spectrum. i use bluetooth signal
as my source signal because of its frequency range. i also look up the
specification of this bluetooth signal’s power, it’s about 20dBm. However, my
received signal from usrp value is large more than 20dBm,
it’s about 70dBm. i do not know what should i modify from spectrum_sense.py. Is
it the gain control cause? i am now in trouble,any help would be appreciate.

The USRP doesn’t give you absolute power in dBm, it gives you relative
power in dB. If you want calibrated values, you’ll have to use a signal
source with a known power output to obtain a reference level, and
compare your Bluetooth signal to that.

–n

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