function [b,a] = un_buttap(N,Omegac);
%   b=Ha(s)分子多項(xiàng)式系數(shù)
%   a=Ha(s)分母多項(xiàng)式系數(shù)
%   N=巴特沃茲模擬原型濾波器的階次
%   OmegaC=截止頻率弧度/秒
[z0,p0,k0] =buttap(N);
    p=p0*Omegac;
    k=k0*Omegac^N;
    B=real(poly(z0));
    b=k*B;
    a=real(poly(p));