产生： >> symbol = {'1','2','3','4','5','6','7','8','9','*','0','#'}; lfg = [697 770 852 941]; % Low frequency group hfg = [1209 1336 1477]; % High frequency group Fs=8000; lwg=2*pi*lfg/Fs; hwg=2*pi*hfg/Fs; a=zeros(2,4); b=zeros(2,3); for p=1:4, a(1,p)=sin(lwg(p)); end for p=1:4, a(2,p)=-2*cos(lwg(p)); end for q=1:3, b(1,q)=sin(hwg(q)); end for q=1:3, b(2,q)=-2*cos(hwg(q)); end for i=1:4, c(i,:)=[0,a(1,i)]; end d=zeros(4,3); for i=1:4, d(i,:)=[1,a(2,i),1]; end e=zeros(3,2); for i=1:3, e(i,:)=[0,b(1,i)]; end f=zeros(3,3); for i=1:3, f(i,:)=[1,b(2,i),1]; end x=zeros(1,205); x(1)=1; for i=1:4, S1(i,:)=filter(c(i,:),d(i,:),x); end for i=1:3, S2(i,:)=filter(e(i,:),f(i,:),x); end n=0:204; for i=1:4, for j=1:3, subplot(4,3,3*(i-1)+j), plot(n,S1(i,:)+S2(j,:));title(['Symbol "', symbol{3*(i-1)+j},'": [',num2str(lfg(i)),',',num2str(hfg(j)),']']) set(gca, 'XLim', [0 205]); ylabel('Amplitude'); if (3*(i-1)+j)>9, xlabel('n'); end end end set(gcf, 'Color', [1 1 1], 'Position', [1 1 1280 1024]) annotation(gcf,'textbox', 'Position',[0.38 0.96 0.45 0.026],... 'EdgeColor',[1 1 1],... 'String', '\bf Time response of each tone of the telephone pad', ... 'FitBoxToText','on'); 

检测： for i=1:4, for j=1:3, X(3*(i-1)+j,:)=S1(i,:)+S2(j,:); end end >> ff=[697 770 852 941 1209 1336 1477]; k=[18,20,22,24,31,34,38]; for choicetone=1:12; v=zeros(7,3); for i=1:7, for j=1:205, v(i,1)=2*cos(2*pi*k(i)/205)*v(i,2)-v(i,3)+X(choicetone,j); v(i,3)=v(i,2); v(i,2)=v(i,1); end end for i=1:7, X2(i)=v(i,1)^2+v(i,2)^2-2*cos(2*pi*k(i)/205)*v(i,1)*v(i,2); end subplot(4,3,choicetone), end stem(ff,sqrt(X2));