Using smithplot for a smith chart, can't get normalized impedance values to display properly
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Hey guys. As the title suggests, I've been trying to plot the normalized impedance values depending on ω, however when I call the command, the values are horribly misaligned. Refer to the code and the screenshot for further info. What am I doing wrong?
clc;
s = smithplot;
% Define the frequency range (20 MHz to 50 MHz)
f_start = 20e6;
f_stop = 50e6;
f_step = 1e6;
f = f_start:f_step:f_stop;
% Define the load parameters
C = 200e-12;
L = 100e-9;
R = 1000;
% Calculate the angular frequency
omega = 2*pi*f;
% Calculate the reactance
X = omega * L - 1 ./ (omega * C);
% Calculate the impedance of the load
ZL = R + 1i * X;
% Define the characteristic impedance of the transmission line (Z0 = 120 * pi Ohms)
Z0 = 120 * pi;
% Normalize the impedance of the load
ZL_normalized = ZL / Z0;
% Plot the normalized impedance on a Smith chart
hold all;
plot(real(ZL_normalized),imag(ZL_normalized),'LineWidth',2);

2 Comments
Star Strider
on 17 Feb 2023
You need to plot directly to the smithplot.
Try something like this —
% clc;
% s = smithplot;
% Define the frequency range (20 MHz to 50 MHz)
f_start = 20e6;
f_stop = 50e6;
f_step = 1e6;
f = f_start:f_step:f_stop;
% Define the load parameters
C = 200e-12;
L = 100e-9;
R = 1000;
% Calculate the angular frequency
omega = 2*pi*f;
% Calculate the reactance
X = omega * L - 1 ./ (omega * C);
% Calculate the impedance of the load
ZL = R + 1i * X;
% Define the characteristic impedance of the transmission line (Z0 = 120 * pi Ohms)
Z0 = 120 * pi;
% Normalize the impedance of the load
ZL_normalized = ZL / Z0;
% Plot the normalized impedance on a Smith chart
hold all;
s = smithplot(real(ZL_normalized),imag(ZL_normalized),'LineWidth',2);
I do not know what you are plotting, and while I understand about Smith charts, I do not have any of the Toolboxes that support them, so I have no direct experience with them in MATLAB.
.
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