example 5.4

ZL=60-1j*80;Z0=50;f0=2e9;

Z0=50;D3=1/8;Dstep=.001;

drange=[.1:Dstep:.9];

 

Zin4=zeros(numel(drange),numel(drange));

s11=zeros(numel(drange),numel(drange));

 

[D_1,D_2]=meshgrid(drange);

 

D1=.5; D2=.5;

% Zin=Z0*(ZL+1j*Z0*tan(2*pi*D))/(Z0+1j*ZL*tan(2*pi*D)) ;

% Zin_open_shunt=Z0/(1j*tan(2*pi*D))

D1=drange;D2=D1;

for k=1:1:numel(D1)

    for s=1:1:numel(D2)

        Zin_stub1=Z0./(1j*tan(2*pi*D1(k)));

        Zin2=(Zin_stub1.^-1+ZL.^-1).^-1;

        Zin3=Z0*(Zin2+1j*Z0*tan(2*pi*D3))./(Z0+1j*Zin2*tan(2*pi*D3)) ;

        Zin_stub2=Z0./(1j*tan(2*pi*D2(s)));

        Zin4(k,s)=(Zin_stub2.^-1+Zin3.^-1).^-1;

        s11(k,s)=(Zin4(k,s)-Z0)/(Zin4(k,s)+Z0);

     end

end

 

figure(1);surf(abs(s11),'LineStyle','none');

ax=gca

ax.PlotBoxAspectRatio=[1 1 1] 

 

one way to spot |s11| minima is manually moving view point and using the marker