PRACTICAL MATLAB® FOR ENGINEERS PRACTICAL MATLAB

Analog and Digital Filters 611

mag1= abs(H1);

phase1=angle(H1);

figure(1)

subplot(1,2,1)

plot(w,mag1)

xlabel(‘frequency in rad/sec’);

ylabel(‘Magnitude’);

title(‘Magnitude of H(w) vs. w [for R=L=C=1]’);

subplot(1,2,2)

plot(w,phase1*180/pi)

xlabel(‘frequency in rad/sec.’);

ylabel(‘Angle in degrees’);

title(‘Phase of H(w) vs. w [for R=L=C=1]’)

% part(c)

L=1/2;C=1/2; R=1; a=R*L*C;

num2 = R;

den2 = [a L R];

H2 = freqs(num2,den2,w);

mag2 = abs(H2);

phase2 = angle(H2);

figure(2)

subplot(1,2,1)

plot(w,mag2)

xlabel(‘frequency in rad/sec.’);

ylabel(‘Magnitude’);

title(‘Magnitude of H(w) vs. w [for L=C=1/2,R=1]’);

subplot(1,2,2)

plot(w,phase2*180/pi)

xlabel(‘frequency in rad/sec’);

ylabel(‘Angle in degrees’);

title(‘Phase of H(w) vs. w [for L=C=1/2,R=1]’)

disp(‘**************************************************’)

disp(‘******* M A T L A B ***** R E S U L T ************’)

disp(‘**************************************************’)

disp(‘Solution to part (c) ‘)

disp(‘Coefficients of numerator of trans. function [LPF/ with

L=C=1/2,R=1]’)

disp(num2)

disp(‘Coefficients of denominator of trans. function [LPF/lp2lp/wc=2]’)

disp(den2)

tf(num2,den2)

disp(‘**************************************************’)

figure(3)

[P,Q]=lp2lp(num1,den1,2);

Hlp2lp=freqs(P,Q,w);

mag3=abs(Hlp2lp);

phase3=angle(Hlp2lp);

subplot(1,2,1)

plot(w,mag3)

xlabel(‘frequency in rad/sec.’);