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What's wrong with filter function?
Posted:
Dec 7, 1996 10:41 AM


I found the first value of filter function is not correct.
For example, I want to find response to the Kronecker delta function of the following discrete transfer function
z X(z) =  2 z  z  1
where x(0) = 0 and x(1) = 1.
Actually, this transfer function is Fibonacci sereis
x(k + 2) = x(k + 1) + x(k)
since inverse z transformation is equal to the response to the Kronecker delta function. I did followings:
b = [1 0]; % Numerator. a = [1 1 1]; % Denominator. k = [1 zeros(1, 40)]; % Kronecker delta 0 <= k <= 40. x = filter(n, d, k)
x =
Columns 1 through 6
1 1 2 3 5 8
Columns 7 through 12
13 21 34 55 89 144
.................. You see x(0) is 1 instead of 0.
x(0) should be 0. What's wrong?



