Butterworth逼近 Go)-1+ Hn 复延拓 5=j而 西=一下 =(ys”3 c H.方( ) n Hn G 2 2 1 w w + = Butterworth逼近 复延拓 s = jw w = - js 2 2 w = -s ( ) n n n s 2 2 w = -1 ( ) ( ) n n n s H G s 2 2 1+ -1 - =