On Wed, Feb 19, 2014 at 6:26 AM, Lebowski80 <[email protected]> wrote:
> Hello everyone, > > Before to explain my problem I give some technical information about my > hardaware. I'm using USRPs v1 and the boards integrated are XCVR2450 > Transceivers. > > I'm using the script usrp_spectrum_sense.py in a USRP to detect a signal in > a ISM channel. To have a signal expressed in db I did this simple operation > to the received signal: > > signal_db = 20*(math.log10(math.sqrt(m.data[0]/tb.slot_number))) > > I can control the signal transmitted in the ISM channel; so, I know exactly > the time when there is a signal to be detected in the channel. During the > first hours the USRP detects the signal giving me a value of around 40 db > but after some hours such a detected signal decreases up to roughly 10 db > and it does not change anymore regardless of the signal transmitted in the > ISM channel. Only if I kill the process running the usrp_spectrum_sense.py > script and execute it again, the USRP starts to detect again the 40 db > value. The signal to be detected in the ISM channel is always the same. Can > anyone tell me which is the problem? > > Thanks in advance. > I have no clue, but my first (and only) guess would be the automatic gain control (AGC) on the USRP hardware. If you figure it out, please let us know! best, aditya
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