fg_06_02.m

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

% fg_06_02  Analog Butterworth gain.
N=500; L=[2 4 6]; 
xt=[2.1 2.2 2.1]; rad1=10; dB0=-40;
rad=linspace(0,rad1,N);
sp_fig(1,8,4);
axis([0 rad1 dB0 0]);
set(gca,'fontsize',16);
clr=['r' 'g' 'b'];
for plt=1:length(L),
   P=1./(1+rad.^(2*L(plt)));
   dB=10*log10(max(10^(dB0/10),P));
   line(rad,dB,'color',clr(plt),'linewidth',1.5);
   y=dB(round(xt(plt)*N/rad1));
   h=text(xt(plt)+.1,y,['L=',num2str(L(plt))]);
   set(h,'fontsize',16);
end
grid;
set(gca,'xtick',[0:1:10]);
xlabel('Frequency \omega (rad/s)');
ylabel('Butterworth power gain (dB)');