fg_07_13.m

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

% fg_07_13          Sinusoid and white noise (6 plots)
sp_fig(1);
set(gcf,'defaultaxesfontsize',14);

% Compute all the functions.
N=100; ns=19;
phi=zeros(2,N);
x=sin(2*pi*10*([0:N-1]-ns)/N);
rxx=autocorr(x,1,N);
phi(1,:)=rxx(1:N)';
randn('seed',123);
xr=randn(1,N);
x(2,:)=xr*sqrt(10/sum(xr.^2));
ex2=sum(x(2,:).^2)/N;
phi(2,:)=real(ifft(ex2*ones(1,N)));
clr=['r' 'b'];
for m=1:2,
   subplot(3,2,m);
   line(0:N-1,x(m,:),'color',clr(m)); grid on;
   ylabel('x(t)');
   text(110,-1.3,'t','fontname','times','fontsize',14);

   subplot(3,2,m+2);
   y=fftshift(phi(m,:));
   line(-N/2:N/2-1,y,'color',clr(m),'marker','*');
   axis([-N/2 N/2 1.1*min(y) 1.1*max(y)]); grid on;
   ylabel('\phi_{xx}(k)');
   text(58,-.7+.685*(m-1),'k','fontname','times','fontsize',14);
   h(1)=gca;

   subplot(3,2,m+4);
   P=abs(fft(phi(m,:)));
   bar2([-N/2:N/2-1]/N,fftshift(P),clr(m)); grid on;
   axis([-50/N 50/N 0 1.1*max(P)]);
   ylabel('P(\nu)');
   text(58/N,-4+3.985*(m-1),'\nu','fontname','times','fontsize',14);
   h(2)=gca;
end
set(h,'ytick',[0 .1]);