How to retrieve the baseband signal strengh

Hi all I use xlating filter to retrieve the baseband signal and I use
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
/ (sample count). With this way
all the channel’s rssi result are the same(very close consider the same)
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


Should do the trick

Principal Investigator
Shirleys Bay Radio Astronomy Consortium