一.变换(Z- transforms) X()=∑X(m06(t-nT) 拉氏变换:X(S)=∑X( nTo)e 引入变量z=el,则 X(D=∑X(nTZ” X(团即为脉冲序列(t)的Z变换记为X(Z)=ZX(t) ZX()=ZX'()=X(z) (1)级数求和 由X(=∑X(mI)z",展开有 X(=X(0)+X(T0)z+X(2T)Z+…+X(nT)Z”+…(1) 如果(1)时能写成闭式则可求得变换§4 Z变换 ( ) (1) , Z . X(Z) X(0) X(T ) (2 ) ( ) (1) X(Z) X(nT )Z , [ ( )] [ ( )] X(Z) ( ) , ( ) [ ( )] X(Z) X(nT )Z z e , : X (S) X(nT )e X (t) X(nT ) (t -nT ) 0 2 0 1 0 n 0 -n 0 * * * n 0 -n 0 T S n 0 -nT S 0 * n 0 0 0 * 0 0 如 果 时能写成闭式则可求得 变 换 由 展开有 即为脉冲序列 的 变 换 记 为 引入变量 则 拉氏变换 = + + ++ + = = = = = = = = − − −  =  =  =  =     n Z X T Z X nT Z Z X t Z X t X Z X t Z X Z Z X t  一.Z变换(Z-transforms) (1) 级数求和