The a-‘l’ransform I5giirc.. Tlie houndary of thc.
Trang 1318 I D The a-‘l’ransform
I5giirc 13.3: Region of convorgmrt of t t i t ~ fundiorl X ( z ) from Example 13.2
For U = I the seyiicnct’ x[kj represents the unit step finictiori &[kj from ( 1 2.6)
Its z-transform i s
2
The z-transform of t,hc a l e h i t l e d exponriil id s e q i m i c e from Figure 13.4
.r[k- = -ak c[ k - 11, n F Q (13.7)
is
Figure 13.4: Exariiple of a left-hidetl expoiicntinl scqiwricc
This siim convcrgcs for /z/ i [ U / , which riiwiis all valiiw of z in the cornplcx planc that licl witliiri a circle of radius a (see Figure 13.5) Tlie houndary of thc