How to retrieve the baseband signal strengh

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.

On 03/29/2011 04:51 AM, James Jordan wrote:

channels’ signal strengh.

RSSI = AVG(II + QQ) 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