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Topic: What's wrong with filter function?
Replies: 1   Last Post: Dec 9, 1996 6:18 AM

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D.J. Yeo

Posts: 1
Registered: 12/7/04
What's wrong with filter function?
Posted: Dec 7, 1996 10:41 AM
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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?





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