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Evo8
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Homework Statement
Consider the following Z tranform
[itex]X(z)=\frac{z^{-1}}{1-2z^{-1}+2z^{-2}}[/itex]
Calculate the poles and resides by hand.
Homework Equations
To find residue at pole p1
[itex](z-p_{1})X(z)z^{k-1}[/itex] Evaluate at [itex]z=p_{1}[/itex]
The Attempt at a Solution
OK so I've taken the X(z) and converted to positive power of z by multiplying by z^2/z^2
I get [itex]X(z)=\frac{z}{z^{2}+2z+2}[/itex]
I know there is 1 zero at z=o.
For the poles I've used the quadratic equation on the denominator. I come up with
$$p1=\frac{-2\pm\sqrt{-4}}{2} p2=\frac{-2 \pm\ 2j}{2}$$
simplifys to
$$p1=-1-1j$$
$$p2=-1+1j$$
Ok so I am stuck on finding the residues.
The way I see using the above formula I end up with a 0 in the denominator. I know this incorrect. Am I missing some sort of simplification before i evaluate at z=p?
If I take [itex]z^{2}+2z+2[/itex] and substitute [itex]z=-1-1j[/itex] I get 0.
When I use the equation
[itex](z-p_{1})X(z)z^{k-1}[/itex] Evaluate at [itex]z=p_{1}[/itex]
and substitute z with p1 that first term in the parenthesis = o. (p1-p1)=0.
Should something cancel out before i evaluate z=p1so I don't get the 0 in the numerator or denominator? If so I don't see it. I've played with the numbers and moved them around for a couple of days now and I juts don't see it. It doesn't look complicated to me but it never comes out not 0.
any help is appreciated! Thanks!