fg_03_16.m

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

% fg_03_16  Aliasing.
n=0:500; sig=150;

% Original spectrum.
X=exp(-(n/sig).^2);
sp_fig(1);
subplot(3,1,1);
axis([0 500 0 1.2]);
set(gca,'fontsize',16);
line(n,X,'color','k'); grid;
ylabel('{X}(j\omega); \omega=2\pi{f}');
h=text(155,1.1,'Spectrum of original signal');
set(h,'fontsize',16);

% Spectrum of impulse samples.
subplot(3,1,2);
axis([0 500 0 1.2]);
set(gca,'fontsize',16);
line(n,X,'color','k'); grid;
line(n,X(501:-1:1),'color','k');
Xhat=X+X(501:-1:1);
line(n,Xhat,'color','k','linestyle','--');
h=text(155,1.1,'Aliasing components and aliased spectrum');
set(h,'fontsize',16);

% Spectrum of reconstructed signal.
subplot(3,1,3);
axis([0 500 0 1.2]);
set(gca,'fontsize',16);
line(n,[Xhat(1:251),zeros(1,250)],'color','k'); grid;
h=text(155,1.1,'Spectrum of reconstructed signal');
set(h,'fontsize',16);
xlabel('Frequency ({f }) in Hz');