Wiley signals and systems e book TLFe BO 333

I D The a-‘l’ransform 318 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 ( 2.6) Its z-transform i s Z{E[kj}= (13.61 z - I ’ 1x1 > The z-transform of t,hc a lehitled 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