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Z-Transform is not producing expected solution

Jon Steller
Posted 2 years ago

I am trying to get Mathematica to output the Z-transform of x[n]=-u[n-1]. I know what the z-transform of this function should be before and after simplification however, I have not been able to get Mathematica to produce the expected output. Any suggestions? Am I using the function incorrectly? Or am I getting the correct result and not understanding what I am getting? Attached are the expected results, simplified and unsimplified, and my various attempts at using the Z-Transform command.

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POSTED BY: Jon Steller
3 Replies
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What two steps are you talking off?

You have to now which is your variable, is it n or is it u? After this only one step is left.

If you are expecting the following result:

-(1/(1 - z^-1)) + 1

You could perform the inverse transform:

 InverseZTransform[-(1/(1 - z^-1)) + 1, z, x]

Out[8]= -1 + UnitStep[-x]

Robert
POSTED BY: Robert Nowak

Hi Jon

I am afraid, you will have to learn much more about Mathematica syntax.

ZTransform[-u (n - 1), n, z]

Out[1]= (u (-2 + z) z)/(-1 + z)^2



ZTransform[-u (n - 1), u, z]

Out[4]= -(((-1 + n) z)/(-1 + z)^2)

Robert
POSTED BY: Robert Nowak
Jon Steller
Jon Steller
Posted 2 years ago

Thank you for the explanation. If I am required to do this in 2 steps, is there a way to then combine these results and simplify?
POSTED BY: Jon Steller
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