butterworth+chebcv的matlab 程序

				%实现Butterworth模拟滤波器的去归一化并且进行双线性变换子程序u_buttap.m
				function[b,a]=g_bilinear(N,Omegac,fs)
				z = [];
				p =exp(j*((2*(1:2:N-1)-1+N)/(2*N))*pi)
				p=[p;conj(p)];
				p = p(:);
				if rem(N,2)==1   % n is odd
				    p = [p; -1];
				end
				k = real(prod(-p));
				p=p*Omegac;k=k*Omegac^N;
				%B=real(poly(z));
				%b0=k;
				%b=k*B;
				fs=2*fs;
				ad=(fs+p)./(fs-p);
				zd=(fs+z)./(fs-z);
				kd=(prod(fs-z)./prod(prod(fs-p)));
				
				bd=[zd;-ones(length(p)-length(z),1)];
				a=poly(ad);
				b=poly(bd);
				b=b*kd*k;