function [bb,aa,nn]=z_modu(b,a,nu,alpha)
%	[bb,a,nn]=z_modu(b,a,nu,alpha)
% g(k)=cos(pi*alpha*k)*h(k)  <-->  G(z)
% alpha is normalized frequency, i.e.
% a fraction of the half sampling frequency
	b1=b.*exp(-j*pi*alpha*[nu:length(b)+nu-1]);
	a1=a.*exp(-j*pi*alpha*[0:length(a)-1]);
	bb=real(conv(b1,conj(a1)));
	aa=real(conv(a1,conj(a1)));
	nn=nu;