SmithChart(option)

function figNumber = SmithChart(option)
%% Usage: 
%  SmithChart(option)
%% Purpose: 
%  creates Smith chart display
%% Parameters:
%  option  =  0 <-- Z-Smith Chart is created  (black color, solid line)
%  option  =  1 <-- Y-Smith Chart is created  (black color, solid line)
%  option  =  2 <-- ZY-Smith Chart is created (black color,Z-Chart- solid line, Y-Chart - dashed line)
%% Credit
%  Developed By : Chiranjit Bordoloi
%  Dated : 01-April-2011
%  Course : ECE527 | High Frequency Electronics
%----------------------------------------------------------------------------------------------------

% program starts
  figNumber = figure;

% define X and R circles
  X = [0.2 0.5 1 2 5];
  R = [0.2 0.5 1 2 5];

% we want to plot smooth cirlces with 101 points
  alpha = 2*pi*(0:0.01:1);

% if no arguments are not specified we assume Z-chart
  if nargin<1
      option = 0;
  end;

% draw a white circle
  chart_color = [0 0 0];                      %set color  =  black
  patch(cos(alpha),sin(alpha),'-','edgecolor',chart_color,'facecolor',get(gca,'color'));
  hold on;
  plot([-1 1],[0 0],'color',chart_color);

  for rr = R
      xc = rr/(1+rr);                         %x position of the center
      rd = 1/(1+rr);                          %radius of the circle
   
      % plot circles
        if (option == 0 | option == 2)
            plot(xc+rd*cos(alpha),rd*sin(alpha),'-','color',chart_color);
        end;
        if option == 1
            plot(-xc-rd*cos(alpha),rd*sin(alpha),'-','color',chart_color);
        end;
        if option == 2
            plot(-xc-rd*cos(alpha),rd*sin(alpha),'-','color',chart_color);
        end;
   end;
   
   for xx = X
       xc = 1;                                %x position of the center
       yc = 1/xx;                             %y position of the center
       rd = 1/xx;                             %radius of the circle
       alpha_xx =  2*atan(xx)*(0:0.01:1);
       if (option == 0 | option == 2)
           plot(xc-rd*sin(alpha_xx),yc-rd*cos(alpha_xx),'-','color',chart_color);
           plot(xc-rd*sin(alpha_xx),-yc+rd*cos(alpha_xx),'-','color',chart_color);
       end;
       if (option == 1)
           plot(-xc+rd*sin(alpha_xx),yc-rd*cos(alpha_xx),'-','color',chart_color);
           plot(-xc+rd*sin(alpha_xx),-yc+rd*cos(alpha_xx),'-','color',chart_color);
       end;
       if (option == 2)
           plot(-xc+rd*sin(alpha_xx),yc-rd*cos(alpha_xx),':','color',chart_color);
           plot(-xc+rd*sin(alpha_xx),-yc+rd*cos(alpha_xx),':','color',chart_color);
       end;
    end

% annotate smith chart
  Z_text_color = [0.5 0 0];
  Y_text_color = [0 0 0.5];
  
  if option  == 0
      for rr = R
          xc = rr/(1+rr);                     %x position of the center
          rd = 1/(1+rr);                      %radius of the circle
          text(xc-rd,0,num2str(rr,'%.1f'), ...
          'horizontalalignment','left','VerticalAlignment','bottom',...
          'color',Z_text_color,'Rotation',90);
      end;   
      
      for xx = X
          alpha_xx =  2*atan(1/xx);
          text(1.1*cos(alpha_xx),1.1*sin(alpha_xx),num2str(xx,'+%.1f'), ...
          'horizontalalignment','center','VerticalAlignment','middle',...
          'color',Z_text_color);
          text(1.1*cos(alpha_xx),-1.1*sin(alpha_xx),num2str(xx,'-%.1f'), ...
          'horizontalalignment','center','VerticalAlignment','middle',...
          'color',Z_text_color);
      end;  
      text(-1.1,0,'0.0', ...
      'horizontalalignment','center','VerticalAlignment','middle',...
      'color',Z_text_color);
      text(1.1,0,'\infty', ...
      'horizontalalignment','center','VerticalAlignment','middle',...
      'color',Z_text_color);
      text(1.5,-1.0,'CopyRight : Chiranjit Bordoloi | 2011');
   end;

   if option  == 1
       for rr = R
           xc = -rr/(1+rr);                   %x position of the center
           rd = -1/(1+rr);                    %radius of the circle
           text(xc-rd,0,num2str(rr,'%.1f'), ...
           'horizontalalignment','right','VerticalAlignment','top',...
           'color',Y_text_color,'Rotation',90);
       end;   
       for xx = X
           alpha_xx =  2*atan(1/xx);
           text(-1.1*cos(alpha_xx),-1.1*sin(alpha_xx),num2str(xx,'+%.1f'), ...
           'horizontalalignment','center','VerticalAlignment','middle',...
           'color',Y_text_color);
           text(-1.1*cos(alpha_xx),+1.1*sin(alpha_xx),num2str(xx,'-%.1f'), ...
           'horizontalalignment','center','VerticalAlignment','middle',...
           'color',Y_text_color);
       end;  
       text(1.1,0,'0.0', ...
       'horizontalalignment','center','VerticalAlignment','middle',...
       'color',Y_text_color);
       text(-1.1,0,'\infty', ...
       'horizontalalignment','center','VerticalAlignment','middle',...
       'color',Y_text_color);
       text(1.5,-1.0,'CopyRight : Chiranjit Bordoloi | 2011');
   end;
   
   if option  == 2
       for rr = R
           xc = rr/(1+rr);                     %x position of the center
           rd = 1/(1+rr);                      %radius of the circle
           text(xc-rd,0,num2str(rr,'%.1f'), ...
           'horizontalalignment','left','VerticalAlignment','bottom',...
           'color',Z_text_color,'Rotation',90);
       end;   
      
       for xx = X
           alpha_xx =  2*atan(1/xx);
           text(1.1*cos(alpha_xx),1.1*sin(alpha_xx)-0.05,num2str(xx,'+%.1f'), ...
           'horizontalalignment','center','VerticalAlignment','middle',...
           'color',Z_text_color);
           text(1.1*cos(alpha_xx),-1.1*sin(alpha_xx),num2str(xx,'-%.1f'), ...
           'horizontalalignment','center','VerticalAlignment','middle',...
           'color',Z_text_color);
       end;  
       text(-1.1,0,'0.0', ...
       'horizontalalignment','center','VerticalAlignment','middle',...
       'color',Z_text_color);
       text(1.1,0,'\infty', ...
       'horizontalalignment','center','VerticalAlignment','middle',...
       'color',Z_text_color);
  
       for rr = R
           xc = -rr/(1+rr);                   %x position of the center
           rd = -1/(1+rr);                    %radius of the circle
           text(xc-rd,0,num2str(rr,'%.1f'), ...
           'horizontalalignment','right','VerticalAlignment','top',...
           'color',Y_text_color,'Rotation',90);
       end;
       
       for xx = X
           alpha_xx =  2*atan(1/xx);
           text(-1.1*cos(alpha_xx),-1.1*sin(alpha_xx)+0.05,num2str(xx,'+%.1f'), ...
           'horizontalalignment','center','VerticalAlignment','middle',...
           'color',Y_text_color);
           text(-1.1*cos(alpha_xx),+1.1*sin(alpha_xx),num2str(xx,'-%.1f'), ...
           'horizontalalignment','center','VerticalAlignment','middle',...
           'color',Y_text_color);
       end;  
       text(1.1,0.05,'0.0', ...
       'horizontalalignment','center','VerticalAlignment','middle',...
       'color',Y_text_color);
       text(-1.1,0.05,'\infty', ...
       'horizontalalignment','center','VerticalAlignment','middle',...
       'color',Y_text_color);
       
       text(1.5,0.55,'Red   = Impedance','color',Z_text_color);
       text(1.5,0.50,'Blue  = Admittance','color',Y_text_color);
       text(1.5,-1.0,'CopyRight : Chiranjit Bordoloi | 2011');
       
   end;

   hold off;
   axis image;
   axis off;