here's some Matlab/Octave code to calculate the series R+jX from S11 for
a range of phases, with a constant return loss..
(-30dB as written), and the tabulated values for -20dB and -30dB.
(Now to convert to parallel form)
S11mag = -30; % dB
S11phase = [-180:10:180];
gamma = 10^(S11mag/20)*complex(cos(S11phase/180*pi),sin(S11phase/180*pi));
Z0 = 50;
Z = Z0 * (1+gamma)./(1-gamma);
figure(1)
plot(S11phase,real(Z),'r',S11phase,imag(Z),'g')
legend('real','imag')
xlabel('degrees')
ylabel('Ohms')
grid on
title('|S11| = -30dB')
fprintf('deg R X\n');
for i=1:length(S11phase)
fprintf('%5d %6.2f %6.2f\n',S11phase(i),real(Z(i)),imag(Z(i)));
end
For -20dB
deg R X
-180 40.91 -0.00
-170 41.01 -1.44
-160 41.32 -2.86
-150 41.84 -4.23
-140 42.55 -5.53
-130 43.48 -6.73
-120 44.59 -7.80
-110 45.90 -8.71
-100 47.38 -9.43
-90 49.01 -9.90
-80 50.76 -10.10
-70 52.57 -9.98
-60 54.40 -9.52
-50 56.16 -8.69
-40 57.77 -7.50
-30 59.15 -5.98
-20 60.21 -4.16
-10 60.88 -2.14
0 61.11 0.00
10 60.88 2.14
20 60.21 4.16
30 59.15 5.98
40 57.77 7.50
50 56.16 8.69
60 54.40 9.52
70 52.57 9.98
80 50.76 10.10
90 49.01 9.90
100 47.38 9.43
110 45.90 8.71
120 44.59 7.80
130 43.48 6.73
140 42.55 5.53
150 41.84 4.23
160 41.32 2.86
170 41.01 1.44
180 40.91 0.00
For -30dB
deg R X
-180 46.93 -0.00
-170 46.98 -0.52
-160 47.10 -1.02
-150 47.31 -1.50
-140 47.60 -1.94
-130 47.95 -2.33
-120 48.37 -2.65
-110 48.84 -2.91
-100 49.36 -3.08
-90 49.90 -3.16
-80 50.45 -3.15
-70 51.00 -3.03
-60 51.53 -2.83
-50 52.01 -2.52
-40 52.44 -2.13
-30 52.79 -1.67
-20 53.05 -1.15
-10 53.21 -0.58
0 53.27 0.00
10 53.21 0.58
20 53.05 1.15
30 52.79 1.67
40 52.44 2.13
50 52.01 2.52
60 51.53 2.83
70 51.00 3.03
80 50.45 3.15
90 49.90 3.16
100 49.36 3.08
110 48.84 2.91
120 48.37 2.65
130 47.95 2.33
140 47.60 1.94
150 47.31 1.50
160 47.10 1.02
170 46.98 0.52
180 46.93 0.00
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