Re: [Discuss-gnuradio] how to retrieve the baseband signal strengh

[Marcus D. Leech]

On 03/29/2011 04:51 AM, James Jordan wrote:
> Hi all I use xlating filter to retrieve the baseband signal and I use
> such way the compute the samples
> signal strengh like this: a = sqrt(i * i + q * q)  (i and q means the
> complex signal's real part and image part)
> then compute the average signal strengh: rssi = (sum of all sample
> strengh) / (sample count). With this way
> all the channel's rssi result are the same(very close consider the
> same) but actually they are not the same.
> Is there any wrong in my method? I do not need the actual rssi value
> but just need a way to distinguish the
> channels' signal strengh.
>   
RSSI = AVG(I*I + Q*Q)  there shouldn't be a sqrt() term in there. 
Remember that the ADCs are
  sampling *voltage*, and power is proportional to the square of the
voltage.

source---->complex-to-mag-squared---->single-pole-iir-filter

Should do the trick


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