ex5_5.m

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%%%%%%%%%%%%%%%%%% Example 5.5 %%%%%%%%%%%%%%%%%%
%   Discrete-Time Control Problems using        %
%       MATLAB and the Control System Toolbox   %
%   by J.H. Chow, D.K. Frederick, & N.W. Chbat  %
%         Brooks/Cole Publishing Company        %
%                September 2002                 %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%   ---- frequency response of ZOH ----
%
clear
disp('Example 5.5')

fs = 10; Ts = 1/fs;             % sampling frequency and period
f = [0:0.1:30]';                % frequency points from 0 to 30 Hz
Gh0 = (1-exp(-j*Ts*2*pi*f))./(j*2*pi*f);  % './' is entry-wise divide
disp('The warning is due to divide by zero at zero frequency, define DC gain separately')
Gh0(1) = Ts;                    % define DC gain separately
figure
title('Frequency response of the Zero-Order Hold')
subplot(2,1,1) 
plot(f,abs(Gh0)),grid           % magnitude plot
ylabel('Magnitude')
subplot(2,1,2), 
plot(f,angle(Gh0)*180/pi),grid  % phase plot
ylabel('Phase (deg)')
xlabel('Frequency (Hz)')
%%%%%%%%%%