exa4_3.m

新版Matlab 7辅助信号处理技术与应用

% exa4-3_Chebyshev_II for example4-3
% Chebyshev II analog lowpass filter

clear all;
n=0:0.01:2;
for i=1:4
    switch i
        case 1
            N=1;
        case 2
            N=3;
        case 3
            N=5;
        case 4
            N=7;
    end
    Rs=10;
    [z,p,k]=cheb2ap(N,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