% 《數字信號處理教程——MATLAB釋義與實現》第四章演示程序
%  電子工業出版社出版  陳懷琛編著 2004年8月
%  數字濾波器頻帶變換演示
%  call_dlp2bs.m 數字低通濾波器到數字帶阻濾波器
%
function []=call_dlp2bs(h1,h2)
axes(h1);hold off
plot([0,0],[-1.2,1.2],'linestyle','-.','color','g');hold on
plot([-2,2],[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([-2,2],[0,0],'linestyle','-.','color','g');axis([-1.2,1.2,-1.2,1.2]);


w0=0.2*pi;   %低通濾波器的截止頻率(指過渡濾波器，而非最終要設計的濾波器，它的截止頻率在wc（dtransform.m中)設置
w=0:0.1:2*pi;  %在這里可以更改其間隔,如果改成0:0.1:2*pi,則下面的判斷要改成abs(w(i))<w0  | abs(w(i))>2*pi-w0
zlp=exp(j*w);

[zbs0,zbs1]=dtransform(w,'lp2bs');

mark1=1;

for k=1:2
    %注意加下面這幾行語句的作用，因為對于w=0 時，zlp=1,此時用plot(zlp)繪出來的點為(1,1)點，
    %可以考慮去除這幾行語句，同時把i改為從i=1:length(w),看看實驗的結果,
    axes(h1);
    plot(zlp(1)+0.0001j,'linestyle','o','color','r');axis([-1.2,1.2,-1.2,1.2]);axis('equal');hold on
    axes(h2);
    if k==2
       plot(zbs0(1)+0.001j,'linestyle','o','color','r');axis([-1.2,1.2,-1.2,1.2]);axis('equal');hold on
   else
       plot(zbs1(1)+0.001j,'linestyle','o','color','r');axis([-1.2,1.2,-1.2,1.2]);axis('equal');hold on
   end
   pause(0.5);
   
    for i=2:length(w)
        %繪制低通濾波器
        axes(h1);
        if (k==2 & mark1==1)
        mark1=0;
        hold off;
        plot([0,0],[-1.2,1.2],'linestyle','-.','color','g');hold on
        plot([-2,2],[0,0],'linestyle','-.','color','g');axis([-1.2,1.2,-1.2,1.2]);
        plot(zlp(1)+0.0001j,'linestyle','o','color','r');axis([-1.2,1.2,-1.2,1.2]);axis('equal');hold on %
        end
        if (abs(w(i))<w0 | abs(w(i)>2*pi-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
        
        %繪制帶阻濾波器
        axes(h2);
        if (k==2)
           if (abs(w(i))<w0 | abs(w(i)>2*pi-w0))
            plot(zbs0(i),'linestyle','o','color','r');axis([-1.2,1.2,-1.2,1.2]);axis('equal');hold on
           else
             plot(zbs0(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 | abs(w(i)>2*pi-w0))
            plot(zbs1(i),'linestyle','o','color','r');axis([-1.2,1.2,-1.2,1.2]);axis('equal');hold on
           else
             plot(zbs1(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