fg_10_19.m

英文书《Digital Signal Processing with Examples in MATLAB》附带的MATLAB实例

% fg_10_19       Decimation & Expansion Spectra
t=0:199; N=800; p=14;
n=0:N-1;
z=zeros(1,N/4);
x1=1.2*t.*exp(-t/20);
x2=[linspace(0,2,40) linspace(2,0,160)];
sp_fig(1);

subplot(3,2,1);
FT=[z z rev(x2) rev(x1) x1 x2 z z];
line([0:2*N-1]/2,[z z rev(x2) rev(x1) x1 x2 z z ],'color','k');
set(gca,'yticklabel',' ','xticklabel',' '); grid on;
dx1=[80 70 10 50 60];
a1=get(gca,'xtick')-dx1;
b1=-1*(ones(1,5));
xlab1=char('-2\pi/T','-\pi/T','0','\pi/T','2\pi/T');
text(a1,b1,xlab1,'fontname','times','fontsize',p);
ylabel('FT\{x\}/T','fontname','times','fontsize',p);

subplot(3,2,2);
line(n,[x1 x2 rev(x2) rev(x1)],'color','k');
set(gca,'yticklabel',' ','xticklabel',' '); grid on;
dx2=[10 50 40 70 60];
a2=get(gca,'xtick')-dx2;
b2=-1*(ones(1,5));
xlab2=char('0','\pi/2T','\pi/T','3\pi/2T','2\pi/T');
text(a2,b2,xlab2,'fontname','times','fontsize',p);
ylabel('DFT=X(\omega)','fontname','times','fontsize',p);

subplot(3,2,3);
line(n,[x1 z z rev(x1)],'color','k'); grid on;
set(gca,'xticklabel',' ');
set(gca,'yticklabel','0||1.0','fontname','times','fontsize',p);
text(a2,b2,xlab2,'fontname','times','fontsize',p);
ylabel('U^{1}(\omega)','fontname','times','fontsize',p);

subplot(3,2,4);
line(2*[0:N/2-1],[x1 rev(x1)],'color','k'); grid on;
set(gca,'xticklabel',' ');
set(gca,'yticklabel','0||0.5','fontname','times','fontsize',p);
dx3=[10 70 50 80 70];
x3=get(gca,'xtick')-dx3;
xlab3=char('0','\pi/2T_2','\pi/T_2','3\pi/2T_2','2\pi/T_2');
y3=-1.5*(ones(1,5));
text(x3,y3,xlab3,'fontname','times','fontsize',p);
ylabel('U^{1D}(\omega)','fontname','times','fontsize',p);

subplot(3,2,5);
line(n,[z x2 rev(x2) z],'color','k'); grid on;
set(gca,'xticklabel',' ');
set(gca,'yticklabel','0||1.0','fontname','times','fontsize',p);
text(a2,b2,xlab2,'fontname','times','fontsize',p);
ylabel('U^{2}(\omega)','fontname','times','fontsize',p);
axis([0 800 0 10]);
xlabel('\omega (rad/s)','fontname','times','fontsize',p);

subplot(3,2,6);
line(2*[0:N/2-1],[x2 rev(x2)],'color','k'); grid on;
set(gca,'xticklabel',' ');
set(gca,'yticklabel','0||0.5','fontname','times','fontsize',p);
text(x3,y3,xlab3,'fontname','times','fontsize',p);
ylabel('U^{2D}(\omega)','fontname','times','fontsize',p);
axis([0 800 0 10]);
xlabel('\omega (rad/s)','fontname','times','fontsize',p);