fg_03_10.m

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

% fg_03_10:  Interpolation via zero insertion in freq. domain.
N=17; K=2; T=.003;
n=0:N-1;
x=sin(2*pi*n.^2/100);
X=fft(x);
Y=[X(1:(N+1)/2),zeros(1,K*N),X((N+1)/2+1:N)];
y=(K+1)*ifft(Y);

% Plot x.
sp_fig(1);
subplot(2,2,1);
axis([0 .05 -1.4 1.4]);
set(gca,'fontsize',16)
line(n*T,x,'linestyle','none','marker','o','color','b'); grid;
xlabel('t (s)'); ylabel('Original x; T_1=3 ms');

% Plot |X|.
subplot(2,2,2);
axis([-1/(2*T) 1/(2*T) 0 4]);
set(gca,'fontsize',16)
amp=abs(fftshift(X));
m=-(N-1)/2:(N-1)/2;
line(m/(N*T),amp,'linestyle','none','marker','o','color','b'); grid;
xlabel('f (Hz)'); ylabel('Amplitude |X|');

% Plot |Y|.
subplot(2,2,3);
axis([-(K+1)/(2*T) (K+1)/(2*T) 0 4]);
set(gca,'fontsize',16)
amp=abs(fftshift(Y));
m=-((K+1)*N-1)/2:((K+1)*N-1)/2;
line(m/(N*T),amp,'linestyle','none','marker','o','color','r'); grid;
xlabel('f (Hz)'); ylabel('Amplitude |Y|');

% Plot LPF output.
subplot(2,2,4);
axis([0 .05 -1.4 1.4]);
set(gca,'fontsize',16)
k=0:(K+1)*N-1;
line(k*T/(K+1),real(y),'linestyle','none','marker','o','color','r');
line(n*T,x,'linestyle','none','marker','*','color','b');
grid; xlabel('t (s)'); ylabel('Interpolated x; T_2=1 ms');