Region of convergence (ROC) sino.n πn →以etag -00<n<0 cos(aw)→∑[π(o-@a+2r)+π6(@+a+2πk] FTs aren't uniform convergence傅里叶变换不是一致收敛 The Fourier transforms aren't continuous,infinitely differentiable functions,so they cannot result from evaluating a z-transform on the unit circle. So it's not strictly correct to think of the Fourier transform as being the z-transform evaluated on the unit circle. 1212 Region of convergence (ROC) ➢The Fourier transforms aren’t continuous, infinitely differentiable functions, so they cannot result from evaluating a z-transform on the unit circle. cos(0 n)  ( 0 0 2 2 ) ( ) k         k k  =−  − + + + + So it’s not strictly correct to think of the Fourier transform as being the z-transform evaluated on the unit circle. FTs aren’t uniform convergence傅里叶变换不是一致收敛 −    n   sin lp c n h n n   = ( )  1, 0, j c lp c H e        =  