If the z-transform of x[n] is X(z)

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Discussion Overview

The discussion revolves around the z-transform of discrete-time signals, specifically focusing on how to express the z-transform of x[n+1] in terms of X(z), the z-transform of x[n]. Participants explore the implications of the shift theorem and its application to both forward and backward shifts in the z-domain.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • Some participants inquire about the z-transform of x[n+1] given that the z-transform of x[n] is X(z).
  • One participant mentions a shift theorem that could be applied to derive the z-transform of x[n+1], suggesting a method involving changing variables in the summation.
  • Another participant expresses confusion regarding the application of the shift theorem, specifically how to relate x[n+1] to X(z) and contrasts it with their findings for x[n-1].
  • There is a reference to the left shift of the z-transform and its usefulness in solving the problem at hand.
  • One participant notes the similarities between the unilateral z-transform and the Laplace transform, particularly in the context of causal systems.
  • A later reply emphasizes the need to rearrange terms in the summation correctly to arrive at the desired result.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the method to derive the z-transform of x[n+1] from X(z), with some expressing uncertainty and others providing differing approaches. The discussion remains unresolved regarding the exact formulation.

Contextual Notes

There are limitations in the discussion regarding the assumptions made about the nature of the signals (e.g., causality) and the specific conditions under which the shift theorem applies. Additionally, the mathematical steps involved in the derivation are not fully resolved.

symsane
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If the z-transform of x[n] is X(z), then what is the z-transform of x[n+1] in terms of X(z) ?
 
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symsane said:
If the z-transform of x[n] is X(z), then what is the z-transform of x[n+1] in terms of X(z) ?
There is a shift theorem, similar to the other kinds of reciprocal transforms. To prove it, just change n to n' in the sum, replace n' by n+1, and then shift the sum back to n.
 


OK I know this Shift Theorem, but I have a problem with it. If the z-transform of x[n] is X(z), I can solve the z-transform of x[n-1] in terms of X(z) and what I found is X(z)z-1+x[-1]. However what is the solution if I want to solve the z-transform of x[n+1] in terms of X(z) ? Or in this case, I can ask this question: How can I solve the z-transform of x[n] if I know the z-transform x[n-1] in terms of X(z) ( As I found x[n-1] = X(z)z-1+x[-1])?
 


I searched the net and I found left shift of z-transform. In this question it is very useful.When we applied this definition we acquire the solution.
 


symsane said:
If the z-transform of x[n] is X(z), I can solve the z-transform of x[n-1] in terms of X(z) and what I found is X(z)z-1+x[-1].
OK, so you are using the UNILATERAL transform (i.e. for causal systems). So, you should see some similarities to the Laplace transform. If you've studied transient response of LTI circuit, the Laplace transform is what you (probably) use there.



symsane said:
... I want to solve the z-transform of x[n+1] in terms of X(z) ?
If you know how to prove the result that you have above for xn-1, then you should be able to do this. Did you read my previous post? Are you having trouble arranging terms in the summation?

EDIT: Sorry, I had a typo in a previous post. I will restate the procedure:

Change n to n' in the sum. Replace n' with n-1. Of course, if you do what I said in the previous post, that will not give you a wrong answer, but it will not help either.
 
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