fg_03_06.m

来自「英文书《Digital Signal Processing with Examp」· M 代码 · 共 54 行

% fg_03_06 - plot of |DFT| over all scales.
N=100; p0=.5; dx=.005;
n=0:N-1;
x=sin(2*pi*(n-50.5)/5)./(n-50.5);
%figure(1); plot(n,x); grid;
A=abs(fft(x));
% Plot DFT amplitude versus index m.
sp_fig(2);
axis([0,50,0,4]);
set(gca,'xtick',[0:10:50],'xticklabel',' | | | | | ');
set(gca,'position',[.1,p0,.7,.93-p0],'fontname','times','fontsize',16);
ylabel('DFT amplitude');
m=0:N/2;
line(m,A(1:N/2+1),'marker','o','color','k'); grid;
title('Amplitude spectrum; N=100');
axes('Position',[.1 p0-.1 .7 .1],'Visible','off');
xx=[-dx,.17-dx,.37-dx,.57-dx,.77-dx,.96-dx];
yy=.75*(ones(1,6));
ss=char('0','0.1N','0.2N','0.3N','0.4N','0.5N');
text(xx,yy,ss,'fontname','times','fontsize',16);
text(1.07,.75,'index (m)','fontname','times','fontsize',16);
% Hz-s axis.
ha1=axes('position',[.1,p0-.1,.7,.01],'ycolor','w');
set(ha1,'xlim',[0 .5],'xtick',[0:.1:.5],'fontname','times','fontsize',16);
axes('Position',[.1 p0-.2 .7 .1],'Visible','off');
text(1.07,.75,'Hz-s (\nu)','fontname','times','fontsize',16);
% radian axis.
ha2=axes('position',[.1,p0-.2,.7,.01],'ycolor','w');
set(ha2,'xlim',[0 4],'xtick',[0:4],'xticklabel',' | | | | ');
axes('Position',[.1 p0-.3 .7 .1],'Visible','off');
xx=[-dx,.24-dx,.49-dx,.73-dx,1-dx];
yy=.75*(ones(1,5));
ss=char('0','\pi/4','\pi/2','3\pi/4','\pi');
text(xx,yy,ss,'fontname','times','fontsize',16);
text(1.07,.75,'rad (\Omega)','fontname','times','fontsize',16);
% Hz axis
ha3=axes('position',[.1,p0-.3,.7,.01],'ycolor','w');
set(ha3,'xlim',[0 5],'xtick',[0:5],'xticklabel',' | | | | | ')
axes('Position',[.1 p0-.4 .7 .1],'Visible','off');
xx=[-dx,.17-dx,.37-dx,.57-dx,.77-dx,.95-dx];
yy=.75*(ones(1,6));
ss=char('0','0.1/T','0.2/T','0.3/T','0.4/T','0.5/T');
text(xx,yy,ss,'fontname','times','fontsize',16);
text(1.07,.75,'Hz (f )','fontname','times','fontsize',16);
% rad/s axis
ha4=axes('position',[.1,p0-.4,.7,.01],'ycolor','w');
set(ha4,'xlim',[0 4],'xtick',[0:4],'xticklabel',' | | | | ')
axes('Position',[.1 p0-.5 .7 .1],'Visible','off');
xx=[-dx,.22-dx,.47-dx,.71-dx,.98-dx];
yy=.75*(ones(1,5));
ss=char('0','\pi/(4T)','\pi/(2T)','3\pi/(4T)','\pi/T');
text(xx,yy,ss,'fontname','times','fontsize',16);
text(1.07,.75,'rad/s (\omega)','fontname','times','fontsize',16);