%   Example program for drawing Bode diagrams with MATLAB

w = logspace(-1,4,100) ;    %   Logarithmically spaced set of 100 radian frequencies
                            %   between 0.1 and 10000 radians/second

A = 50  ;                                  	%   Frequency-independent gain
zs = [0,-100] ;                         	%   Zero locations
ps = [-20,-100+j*500,-100-j*500] ;      	%   Pole locations

%   Compute values of H at the radian frequencies w

H = A ;                     
for n = 1:length(zs),
    if zs(n) == 0, H = H.*j*w ; else H = H.*(1-j*w/zs(n)) ; end
end
for n = 1:length(ps), 
    if ps(n) == 0, H = H./j*w ; else H = H./(1-j*w/ps(n)) ; end
end

%   H now contains the complex transfer function values at the radian
%   frequencies w

%   Draw the Bode diagrams

subplot(2,1,1) ; p = semilogx(w,20*log10(abs(H)),'k') ; set(p,'LineWidth',2) ;
xlabel('Radian Frequency, \omega','FontSize',18,'FontName','Times') ;
ylabel('|H({\itj}\omega)|','FontSize',18,'FontName','Times') ;
grid on ;

subplot(2,1,2) ; p = semilogx(w,angle(H),'k') ; set(p,'LineWidth',2) ;
xlabel('Radian Frequency, \omega','FontSize',18,'FontName','Times') ;
ylabel('Phase of H({\itj}\omega)','FontSize',18,'FontName','Times') ;
grid on ;