fg_05_14.m

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

% fg_05_13   Differentiator example.
L=31; N=2*L+1; T=.05; wc=2*pi*2;
% Weight vector.
k=1:L;
%hh=((-1).^k)./(k*T);
hh=wc*cos(k*wc*T)./(k*pi) - sin(k*wc*T)./(k.^2*pi*T);
h=[-hh(L:-1:1),0,hh(1:L)];
b=h.*window(N,'hamming');
% Amplitude gain.
amp=abs(fft([b,zeros(1,1000-N)]));
sp_fig(1);
subplot(1,2,1);
axis([0 10 0 60]);
set(gca,'fontname','times','fontsize',16);
line(linspace(0,.5/T,501),amp(1:501),'color','k'); grid;
line(.05/T,amp(50),'linestyle','none','marker','*','color','k');
ylabel('Amlitude gain');
xlabel('Frequency (Hz)');
% Sine and cosine.
K=100; k=0:K-1;
x=sin(2*pi*k/20);
y=filter(b,1,x);
subplot(2,2,2);
axis([0 T*K/2 -1 1]);
set(gca,'fontname','times','fontsize',16);
line(T*k,x,'marker','.','color','k'); grid;
ylabel('Input ({\itx})');
subplot(2,2,4);
axis([0 T*K/2 -8 8]);
set(gca,'fontname','times','fontsize',16);
line(T*(k-L),y,'marker','.','color','k'); grid;
xlabel('Time (s)');
ylabel('Output (y)');