- #1
Fisher92
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Homework Statement
The problem was actually for a COMMS assignment that I have finished with the exception of the very last easiest part.
They wanted percentage of power spilled into gaurd bands - have calculated all the powers now need the percentage...
I have two frequency components modulating the carrier and I have calculated power components. I end up with the following:
f(Hz), P(W) - Channel 1
5, 1
10,5
15,2
20,3
25,4
f(Hz), P(W) - Channel 2
5, 1
15,5
20,2
25,3
30,4
Anything above 20kHz is spilled power and I want to know the percentage of spilled power (no that's no my actual results)
The problem is that if I work out the percentages for channel 1 and 2 separately (& then sum) I end up with a higher percentage than if I just summed everything... What is the correct way to do this.
******Example may be easier to follow then my explanation*****
Channel 1:
Total power = 1+5+2+3+4W=15W
Spilled Power (>20kHz)= 4W
Percentage = 4/15*100=26.67%
Channel 2:
Total power = 1+5+2+3+4W=15W
Spilled Power (>20kHz)= 3+4=7W
Percentage = 4/15*100=46.667%
CH1 + ch2 = 46.667+26.67=72% SPILLED
Combined
Total Power = 1+5+2+3+4+1+5+2+3+4=30W
Spilled Power (>20kHz)= 4+3+4=11W
Percentage = 11/30*100=37% SPILLED
Why is there a discrepancy? I get mathematically why this is giving me two different results but which 1 would be the power spilled?