exa4_4.m

matlab应用实例。如：FIR、IIR数字滤波器设计等。

% exa4-4_Elliptic for example4-4
% Elliptic analog lowpass filter prototype

clear all;
n=0:0.01:2;
for i=1:4
    switch i
        case 1
            N=2;
        case 2
            N=3;
        case 3 
            N=4;
        case 4
            N=5;
    end
    Rp=1;
    Rs=10;
    [z,p,k]=ellipap(N,Rp,Rs);
    [b,a]=zp2tf(z,p,k);
    [H,w]=freqs(b,a,n);
    magH2=(abs(H)).^2;
    % Output figure
    posplot=['22' num2str(i)];
    subplot(posplot)
    plot(w,magH2)
    axis([0 2 0 1.1]);
    xlabel('w/wc');
    ylabel('|H(jw)|^2');
    title(['N=' num2str(N)]);
    grid on
end