z1=80;
z2=80;
z3=60;
for f=1:3
d1=pi/4*2./f;
d2=pi/4*2./f;
d3=pi/3*2./f;
Z0=50;
Z=-j*z3*cot(d3);
Y=1./Z;
Y0=1/z1;
Y1=1/z2;
A=(cos(d1)+j*z1*Y*sin(d1))*cos(d1)-z1*Y1*sin(d1)*sin(d1);
B=j*z1*sin(d1)*(cos(d1)+j*z1*Y*sin(d1))+j*1/2*z1*(sin(2*d1));
C=(j*Y1*sin(d1)+Y*cos(d1))*cos(d1)+j*Y1*1/2*sin(2*d1);
D=j*z1*sin(d1)*(j*Y1*sin(d1)+Y*cos(d1))+cos(d1)*cos(d1)
S11(f)=(A+B/Z0-C*Z0-D)/(A+B/Z0+C*Z0+D);
end
g=abs(S11)
plot(f,g)
xlabel('f')
ylabel('S11')
title('S11幅值图')