Re: [Discuss-gnuradio] Unexpected energy peak sensing thermal noise and using usrp_spectrum_sense.py

[Lebowski80]

Thank you for answering but I cannot understand what you mean with "The USRP
is not a measurement receiver". If USRP was not a measurement receiver,
which is its utility? Moreover, if it is not a measurement receiver what is
the result memorized in m.data that is the output of usrp_spectrum_sense.py?
When I use a WiFi antenna I can receive (and measure) the energy of WiFi
channels. The problem arises without antenna becasue USRP measures a signal
that cannot exist! Furthermore, such a signal is always at the beginning of
the sensed bandwidth, so this has not any sense!

Any idea about that? Thank you!


Nick Foster-4 wrote:
> 
> On Wed, 2011-05-25 at 08:51 -0700, Lebowski80 wrote:
>> Hello everyone
>> 
>> I’m using an USRP with a XCVR2450 daughter board working at 2.4 - 2.5
>> GHz. I
>> want to find a threshold between thermal noise and signals energy using
>> the
>> script usrp_spectrum_sense.py and sensing from 2.400 GHz to 2.500 GHz. To
>> do
>> that, I replaced the WiFi antenna with a resistor of 50 Ω to measure the
>> noise. I obtained a very strange peak at the beginning of the bandwidth
>> (around 2.405 GHz) and this result was totally unexpected because I
>> supposed
>> to sense only thermal noise without any particular peak. So, I repeated
>> the
>> experiment from 2.420 GHz to 2.500 GHz and I achieved the same peak
>> always
>> at the beginning of the bandwidth (in this case around 2.425 GHz).
>> Therefore, I'm quite sure this is a problem linked to USRP or to the
>> script
>> usrp_spectrum_sense.py, isn’t it? Can someone give me a hint about that
>> please?
> 
> The USRP is not a measurement receiver, and some small spurs are to be
> expected. You can plan for this, or work around it by changing the LO
> offset at a given center frequency using the advanced tuning parameters:
> http://www.ettus.com/uhd_docs/doxygen/html/structuhd_1_1tune__request__t.html
> 
> --n
> 
>> 
>> Regards 
>> 
> 
> 
> 
> _______________________________________________
> Discuss-gnuradio mailing list
> address@hidden
> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
> 
> 

-- 
View this message in context: 
http://old.nabble.com/Unexpected-energy-peak-sensing-thermal-noise-and-using-usrp_spectrum_sense.py-tp31700266p31705762.html
Sent from the GnuRadio mailing list archive at Nabble.com.