# Spectrum analysis question

Discussion in 'Homework Help' started by drao, Mar 18, 2013.

1. ### drao Thread Starter New Member

Mar 11, 2012
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0
For fill factor=1/2 , periodic rectangular signal,i have to calculate Ak/A1 (db), Ak is the harmonic of order k of the signal.
Ak/A1=1/k when k is odd and 0 when k us even ,And i have the following formula in my textbook:
Ak/A1(db)=20lg(Ak/A1)=nk-n1=nk because n1=0 but what is nk when Ak/A1=0???We also set n1=0 from spectrum analyzer when we measured the signal.

2. ### Papabravo Expert

Feb 24, 2006
10,340
1,850
Whooops. Ak/A1 is never equal to 0. If k=1 then A1/A1 = 1, and the log of 1 is 0.

3. ### drao Thread Starter New Member

Mar 11, 2012
16
0
it is 0 becauyse ak/a1=1/k* (sin(kpi/2))/sin(pi/2) and Ak with k even are all 0.This happens when the signal is periodic rectangular and the fill factor is 1/2.
I know, that one is easy, but the others .

Last edited: Mar 18, 2013
4. ### Papabravo Expert

Feb 24, 2006
10,340
1,850
So tell me what 1/k is equal to for k=1?
Now tell me what the log(1) is equal to.