smith_chart.m

spread spectrum communication will be helpful to you!

function out1 = smith_chart(Action,In1,In2,In3,In4) 
% function out1 = smith_chart(Action,In1,In2,In3,In4)
% Action = 'draw'
%    In1 = [rvalues];
%    In2 = [xvalues];
%    In3 = Zo of line (optional)
%    In4 = position   (optional)

    NSEGSc = 63;
    if strcmp(Action,'draw')
        if nargin <=3
            Zo = 50;
        else
            Zo = In3;
        end;
        
        if nargin <=4
           out1=axes('box','off','xgrid','off','ygrid','off','zgrid','off',...
                     'color','none','nextplot','add','visible','off');
        else
           out1=axes('Units','pixels','position',In4,'box','off','xgrid','off','ygrid','off','zgrid','off',...
                     'color','none','nextplot','add','visible','off');
        end;
        set(out1,'xlim',[-1.1 1.1],'ylim',[-1.1,1.1]);
        xlabel('');
        ylabel('');
        theta = linspace(-pi, pi, NSEGSc);
        
        for r=(In1)
           z     =((r/(r+1) + 1/(r+1)*exp(j*theta)));
           line('xdata',real(z),'ydata',imag(z),'color',[0.5 0.5 0]);
           xpos = (r-1)/(r+1);
            h=text(xpos, 0, ftoa('%4w',r*Zo));
            % h=text(xpos, 0, sprintf('%4.1f',r*Zo));
           set(h, 'VerticalAlignment', 'top', 'HorizontalAlignment', 'right','color',[1 1 1]);
        end;
        
        % draw unit circle , and imag==0 line 
        z = exp(j*theta);
        line('xdata',real(z),'ydata',imag(z),'color',[1 1 0]);
        line('xdata',[-1 1],'ydata',[0 0],'color',[1 1 0]);
        
        v = linspace(0,10,NSEGSc);
        r = [ 0 v.^2];
        
        for x = In2
            z = r+j*x*ones(1,NSEGSc+1);
            g = (z-1)./(z+1);
            line('xdata',real(g),'ydata', imag(g), 'color',[0 0.5 0.5]);
            line('xdata',real(g),'ydata',-imag(g), 'color',[0 0.5 0.5]);
            
            g= ((j*x-1)/(j*x+1));
            xpos = real(g);
            ypos = imag(g);
            
            s = ftoa('%4w',Zo*x);
            h=text([xpos xpos], [ypos -ypos], [' j' s ; '-j' s]);
            set(h(1),'VerticalAlignment', 'bottom','color',[1 1 1]);
            set(h(2),'VerticalAlignment', 'top','color',[1 1 1]);
            if xpos == 0 
               set(h, 'Horizontalalignment', 'center');
            elseif xpos < 0
               set(h, 'Horizontalalignment', 'right');
            end
        end;
        rmin = min(In2);
        rmax = max(In2);
        line('xdata',[(rmin-1)/(rmin+1),(rmax-1)/(rmax+1)],'ydata',[0 0],'color',[1 1 0]);

    else
    
    end;
        
% end;