Re: [Discuss-gnuradio] Measuring RSSI on USRPN200

[Marcus D. Leech]

On 22/10/11 09:41 PM, Bonee Soibam wrote:
> Hi ,
> I am trying to measure the RSSI on an usrpn200 which acts as a
> receiver. i have used the rx_ascii_dft.py and uhd_fft.py both and  i
> have made a host of measurements but the received power is not
> reliable for different transmit powers at different  amplitude of 
> 0.25,0.50 and 0.85 (which i took  randomly ) .. the channel
> attenuation is not less for more transmit power in short ..
>
> Is there any other way to measure the RSSI values besides these two
> apps uhd_fft.py and rx_ascii_dft.py ?i have run a set of measurements
> and the resultant received powers are not reliable at all ,according
> to me . i am still an amateur regarding this . 
> how about running the rssi.v verilog file ? .. will i be able to
> extract the rssi values directly from the fpga ?
>
> Anticipating your feedback in earnest
> Bonee
>
Received power is proportional to the average of the square of the I and
Q voltages.  If you
  use a Complex-to-Mag**2 block, followed by a low-pass filter, you'll
get an (uncalibrated!!)
  received-power estimate.

An increase in *voltage* magnitude from 0.25 to 0.5 should create a
received power increase of
  6dB, since doubling the voltage increases the *power* by a factor of 4
(6dB), assuming a reasonably
  linear channel between TX and RX.

You haven't said what your test setup is: antennae, daughtercards, etc.

What are you using to transmit?  Is it another USRP device, or something
else?




-- 
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org