fg_06_04.m

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

% fg_06_04  Analog Butterworth gain parameters.
N=500; L=2; w1=5; ws=1.4;
w=linspace(0,w1,N);
sp_fig(1,8.5,4);
axis([0 w1 0 1]);
set(gca,'fontsize',16,'position',[0.13 0.16 0.84 0.75]);
set(gca,'xtick',[0],'ytick',[0 .5 1]);
P=1./(1+w.^(2*L));
line(w,P,'color','r');
line([0,1,1],[.5,.5,0],'color','k','linestyle',':');
Pc=1./(1+ws.^(2*L));
line([0,ws,ws],[Pc,Pc,0],'color','k','linestyle',':');
h(1)=text(1-.07,-.04,'\omega_c');
h(2)=text(ws-.07,-.04,'\omega_s');
h(3)=text(-.75,Pc+.01,'1/(1+\lambda^2)');
h(4)=text(.15,.1,'passband');
line([ws,w1],[.07,.07],'color','k','linestyle',':');
line([0,1],[.07,.07],'color','k','linestyle',':');
h(5)=text(3,.1,'stopband');
set(h,'fontsize',16);
xlabel('Frequency \omega (rad/s)')
ylabel('                                   |{\itH(j\omega)}|^2');