1 M-1 Y(z)=∑X(zMW) M=0 e)点ewsM Example M=2, e）-Ke)+x-emy= ∑ − = 1 0 1/ ( ) 1 ( ) M k k M M X z W M Y z = ∑ − = − 1 0 ( 2 )/ ( ) 1 ( ) M k j j k M X e M Y e ω ω π Example M=2, { ( ) ( )} 2 1 ( ) jω jω / 2 jω / 2 Y e = X e + X −e