call_dlp2bp.m

数字信号处理_matlab实现程序,上面有全套的实验代码

% 《数字信号处理教程——MATLAB释义与实现》第四章演示程序
%  电子工业出版社出版  陈怀琛编著 2004年9月
%  数字滤波器频带变换演示
%  call_dlp2bp.m 数字低通滤波器到数字带通滤波器
%
function []=call_dlp2bp(h1,h2)
axes(h1);hold off;
plot([0,0],[-1.2,1.2],'linestyle','-.','color','g');hold on
plot([-1.2,1.2],[0,0],'linestyle','-.','color','g');axis([-1.2,1.2,-1.2,1.2]);
axes(h2);hold off;
plot([0,0],[-1.2,1.2],'linestyle','-.','color','g');hold on
plot([-1.2,1.2],[0,0],'linestyle','-.','color','g');axis([-1.2,1.2,-1.2,1.2]);

w0=0.2*pi;   %低通滤波器的截止频率(指过渡滤波器，而非最终要设计的滤波器，它的截止频率在wc（dtransform.m中)设置
w=-pi:0.1:pi;%在这里可以更改其间隔,如果改成0:0.1:2*pi,则下面的判断要改成abs(w(i))<w0  | abs(w(i))>2*pi-w0
zlp=exp(j*w);

[zbp0,zbp1]=dtransform(w,'lp2bp');

mark1=1;mark2=1;

for j=1:2
    for i=1:length(w)
        %绘制低通滤波器
        axes(h1);
        if (j==2 & mark1==1)
        mark1=0;
        hold off;
        plot([0,0],[-1.2,1.2],'linestyle','-.','color','g');hold on
        plot([-1.2,1.2],[0,0],'linestyle','-.','color','g');axis([-1.2,1.2,-1.2,1.2]);

        end
        if (abs(w(i))<w0)
            plot(zlp(i),'linestyle','o','color','r');axis([-1.2,1.2,-1.2,1.2]);axis('equal');hold on
        else
            plot(zlp(i),'linestyle','o','color','b');axis([-1.2,1.2,-1.2,1.2]);axis('equal');hold on
        end
        
        %绘制带通滤波器
        axes(h2);
        if (j==2)
           if (abs(w(i))<w0)
            plot(zbp0(i),'linestyle','o','color','r');axis([-1.2,1.2,-1.2,1.2]);axis('equal');hold on
           else
             plot(zbp0(i),'linestyle','o','color','b');axis([-1.2,1.2,-1.2,1.2]);axis('equal');hold on
           end
         else
            if (abs(w(i))<w0)
            plot(zbp1(i),'linestyle','o','color','r');axis([-1.2,1.2,-1.2,1.2]);axis('equal');hold on
           else
             plot(zbp1(i),'linestyle','o','color','b');axis([-1.2,1.2,-1.2,1.2]);axis('equal');hold on
           end
         end
        pause(0.2);
      end
      pause(0.5);
end