代码：
b = [1, 0, -1]; a = [1, 0, -0.81]; % [R, p, C] = residuez(b,a); Mp = (abs(p))'
Ap = (angle(p))'/pi %% ----------------------------------------------
%% START a determine H(z) and sketch
%% ----------------------------------------------
figure('NumberTitle', 'off', 'Name', 'Example4.13 H(z) its pole-zero plot')
set(gcf,'Color','white');
zplane(b,a);
title('pole-zero plot'); grid on; %% ----------------------------------------------
%% END
%% ---------------------------------------------- %% --------------------------------------------------------------
%% START b |H| <H
%% 1st form of freqz
%% --------------------------------------------------------------
[H,w] = freqz(b,a,500); % 1st form of freqz magH = abs(H); angH = angle(H); realH = real(H); imagH = imag(H); %% ================================================
%% START H's mag ang real imag
%% ================================================
figure('NumberTitle', 'off', 'Name', 'Example4.13 H its mag ang real imag');
set(gcf,'Color','white');
subplot(2,2,1); plot(w/pi,magH); grid on; %axis([0,1,0,1.5]);
title('Magnitude Response');
xlabel('frequency in \pi units'); ylabel('Magnitude |H|');
subplot(2,2,3); plot(w/pi, angH/pi); grid on; % axis([-1,1,-1,1]);
title('Phase Response');
xlabel('frequency in \pi units'); ylabel('Radians/\pi'); subplot('2,2,2'); plot(w/pi, realH); grid on;
title('Real Part');
xlabel('frequency in \pi units'); ylabel('Real');
subplot('2,2,4'); plot(w/pi, imagH); grid on;
title('Imaginary Part');
xlabel('frequency in \pi units'); ylabel('Imaginary');
%% ==================================================
%% END H's mag ang real imag
%% ================================================== %% ---------------------------------------------------------------
%% END b |H| <H
%% --------------------------------------------------------------- %% --------------------------------------------------------------
%% START b |H| <H
%% 3rd form of freqz
%% --------------------------------------------------------------
w = [0:1:500]*pi/500; H = freqz(b,a,w);
%[H,w] = freqz(b,a,200,'whole'); % 3rd form of freqz magH = abs(H); angH = angle(H); realH = real(H); imagH = imag(H); %% ================================================
%% START H's mag ang real imag
%% ================================================
figure('NumberTitle', 'off', 'Name', 'Example4.13 using 3rd form freqz ');
set(gcf,'Color','white');
subplot(2,2,1); plot(w/pi,magH); grid on; %axis([0,1,0,1.5]);
title('Magnitude Response');
xlabel('frequency in \pi units'); ylabel('Magnitude |H|');
subplot(2,2,3); plot(w/pi, angH/pi); grid on; % axis([-1,1,-1,1]);
title('Phase Response');
xlabel('frequency in \pi units'); ylabel('Radians/\pi'); subplot('2,2,2'); plot(w/pi, realH); grid on;
title('Real Part');
xlabel('frequency in \pi units'); ylabel('Real');
subplot('2,2,4'); plot(w/pi, imagH); grid on;
title('Imaginary Part');
xlabel('frequency in \pi units'); ylabel('Imaginary');
%% ==================================================
%% END H's mag ang real imag
%% ================================================== %% ---------------------------------------------------------------
%% END b |H| <H
%% ---------------------------------------------------------------
结果：
