数字通信第四版原书的例程

				function [nb,db,nw,dw,nl,dl]=dsbadmpc(Fc,order)
				%DSBADMPC   is a function designing filters for DSB SC ADM.
				%   [NB,DB,NW,DW,NL,DL]=DSBADMPC(Fc) 
				%   outputs the bandpass fileter and two lowpass filters for
				%   DSB SC ADM when the carrier frequency is provided.
				
				%       Copyright (c) 1996 by The MathWorks, Inc.
				%       $Revision: 1.1 $  $Date: 1996/04/01 19:38:42 $
				
				if nargin < 2
				    order = 4;
				end;
				Fc=Fc*2*pi;
				[a,b,c,d]=filtm('buttap', 'lp2bp', Fc, Fc/100, 50, order);
				[nb,db]=ss2tf(a,b,c,d);
				[z,p,k]=cheb1ap(order,3);
				a=1.5*Fc*z;
				b=1.5*Fc*p;
				c=real(prod(-b));
				[nw,dw]=zp2tf(a,b,c);
				a=Fc*z/10;
				b=Fc*p/10;
				c=real(prod(-b));
				[nl,dl]=zp2tf(a,b,c);