Question

Consider a signal , x [ n ] = ( 1 2 ) n 1 [ n ] where 1[n] = 0 if n < 0, and 1[n] = 1 if n ≥ 0. The z-transform of x[n - k], k > 0 is z k 1 1 2 z 1 with region of convergence being

Options :

  1. |z| < 2

  2. |z| >2

  3. |z| < 1/2

  4. |z| >1/2

Show Answer

Answer :

|z| >1/2

Solution :

Calculation:

Given that, x ( n ) = ( 1 2 ) n 1 [ n ]

Z Transform (ZT) of x(n) will be,

x ( z ) = z z 1 2 = 1 1 1 2 z 1 ; ROC: | z | > 1 2

And, z ( x ( n k ) ) = z k 1 1 2 z 1 ; ROC: | z | > 1 2

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