- #1
btb4198
- 572
- 10
I took
f(t) = SIN(10*t) +SIN(5*t)
and got this
f(0) = 0
f(1) = -1.5
f(2) = 0.4
f(3) = -0.3
now I tried to do the DFT
Fs = 4Hz
N = 4 samples
3
f[r] = Ʃ x[k]ε^(-j(2πkr/4)
k=0
f[r] = 0 -1.5ε^(-j(2πr/4) + 0.4ε^(-j(2π(2)r/4) -0.3ε^(-j(2π(3)r/4)
f[0] = 0 - 1.5 + 0.4 - 0.3 = -1.4 // now that mean i have a frequency of 0 but I do not..
f[1] = 0 + 1.5j -0.4 -0.3 = 1.5j -0.7
f[2] = 0 +1.5 + 0.4 +0.3 = 2.2
f[3] = 0 -1.5-0.4 +0.3j = -1.9 + 0.3j
ok so I think I am close to understand how to do a DFT but I know that is wrong because I do not have a 0Hz frequency nor do I have a 2Hz frequency
I have 5 and 10
f(t) = SIN(10*t) +SIN(5*t)
and got this
f(0) = 0
f(1) = -1.5
f(2) = 0.4
f(3) = -0.3
now I tried to do the DFT
Fs = 4Hz
N = 4 samples
3
f[r] = Ʃ x[k]ε^(-j(2πkr/4)
k=0
f[r] = 0 -1.5ε^(-j(2πr/4) + 0.4ε^(-j(2π(2)r/4) -0.3ε^(-j(2π(3)r/4)
f[0] = 0 - 1.5 + 0.4 - 0.3 = -1.4 // now that mean i have a frequency of 0 but I do not..
f[1] = 0 + 1.5j -0.4 -0.3 = 1.5j -0.7
f[2] = 0 +1.5 + 0.4 +0.3 = 2.2
f[3] = 0 -1.5-0.4 +0.3j = -1.9 + 0.3j
ok so I think I am close to understand how to do a DFT but I know that is wrong because I do not have a 0Hz frequency nor do I have a 2Hz frequency
I have 5 and 10