Hi Soumaya, the B200 tunes slower and might need up to half a second when tuning further.
You should hence minimize the amount of tuning, and instead of 4MS/s use a higher rate, a larger FFT size, and tune less often. The power normalization is truly, 100%, arbitrary. Since these dB are all "relative to digital 1", they only have linear relation with real-world powers. Best regards, Marcus On 01/13/2017 11:40 AM, Soumaya el barrak wrote: > Dear all, > > I am working with USRP B200 for spectrum sensing, I want to scan the > band from 2.4 to 2.5 Ghz, I use fft size 256, and sample_rate 4M, and > tune _delay 0,001s. I am not sure if the parameters are correctely > chosen because when I try to scan another band without wireless > activities, I still receive hight power levels. Can anyone has any > idea about where I am mistaken ? > > Also, in the formula used to calculate the PSD : > > Power_dB = 10*math.log10(m.data[i_bin]/tb.usrp_rate); > > Normally it is the magnitude squared averaged , I want to know why it > is averaged by the usrp_rate ? > > > Thank you in advance ! > > Soumaya > > -- > > *EL BARRAK Soumaya* > > *Telecommunication & Networking Engineer / Phd Student* > > *Innovative Technologies Laboratory* > > *National School of Applied Sciences of Tangier - (ENSA Tanger)* > > *Abdelmalek Essaâdi University - Morocco* > > *Tel : (+212) 6 65 9 625 40/ (+ 39) 327 198 5064 > <tel:+39%20327%20198%205064>* > > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
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