MATLAB: How to plot Smith chart

Question

Hello. I need to plot Smith chart, having frequency, VSWR, reflection coefficient and phase. I'm fairly new to matlab environment and not sure how to achieve it. Tried already this from mathworks website, it didn't even seemed remotely okay. As it says, I've tried to plot reflection coefficient as gamma. Screen with my data and result I've got:

Answer 1

Hi Mr Taker

There are many ways to plot data on MATLAB Smith charts

1.- basic plot of single impedance

clc;clear all;format long; 
Z0=100;sm1=smithchart;
ZL1=150-1j*200;f0=3e9; % Hz
gamma_L=(ZL1-Z0)/(ZL1+Z0); 
% show ZL1 on Smith chart adding text showing values
if imag(ZL1)<0
sign1='-';
else
    sign1='+';
end
hold all;plot(real(gamma_L),imag(gamma_L),'ro','LineWidth',1.5);
str1=['ZL =' num2str(real(ZL1)) sign1 'j' num2str(abs(imag(ZL1))) ' \rightarrow'];
text(real(gamma_L),imag(gamma_L)+.01,str1,'Color','blue','FontSize',20,'HorizontalAlignment','right','VerticalAlignment','middle');

2.- solving a basic single stub ZLoad match:

the functions I use are as follows:

function [x_data,y_data]=Smith_plotGammaCircle(ax,Z,Z0)
% plot SWR circle, lossless TL
gamma=z2gamma(Z,Z0);  
r=abs(gamma); 
alpha=0:2*pi/100:2*pi;                                       
hold all;
sub_hp2=plot(ax,r*cos(alpha),r*sin(alpha),'-','LineWidth',.5,'Color',[1 .2 0])   
x_data=sub_hp2.XData
y_data=sub_hp2.YData
end
function Smith_plotRefLine2PhaseCircle(ax,Z,Z0)
% plot reference line from origin through ZL to phase reference circle
gamma_L=z2gamma(Z,Z0);                                
a=atan(imag(gamma_L)/real(gamma_L));
plot(ax,[0 cos(a)],[0 sin(a)],'Color',[0 0.7 0],'LineWidth',1)           
end
function a=Smith_plotRefLine2PhaseCircle(ax,Z,Z0)
% plot reference line from origin oppsite to ZL to phase reference circle
% it plots ref line through YL
gamma_L=(Z-Z0)/(Z+Z0)
a=angle(gamma_L)
plot(ax,[0 -real(exp(1j*a))],[0 -imag(exp(1j*a))],'Color',[0 0.7 0],'LineWidth',1)           
end
function Smith_plotZ(ax,Z,Z0)
% add text showing ZL R+jX data, Smith Chart generated externally
gamma=z2gamma(Z,Z0);  
plot(ax,real(gamma),imag(gamma),'ro','LineWidth',1.5)
if imag(Z)<0
sign1='-';
else
    sign1='+';
end
hold all;plot(ax,real(gamma),imag(gamma),'ro','LineWidth',1.5);
str1=['ZL =' num2str(real(Z)) sign1 'j' num2str(abs(imag(Z))) ' \rightarrow'];
text(ax,real(gamma),imag(gamma)+.01,str1,'Color','blue','FontSize',20,'HorizontalAlignment','right','VerticalAlignment','middle');
end

3.- adding reactance/resistance circle sections and a legend

Z0=75; ZL=90+1j*60;
sm1=smithchart; ax=gca; hold all; 
sm1.Values = [.1 .2 .3 .5 1 1.5 2 3.5 5;1 1.5 2 3.5 5 5 5 15 30]
sm1.SubColor=[.2 .2 .2]
gamma_ZL=(ZL-Z0)/(ZL+Z0); gamma_YL=-gamma_ZL
plot(ax,real(gamma_ZL),imag(gamma_ZL),'ro','LineWidth',1.5)
plot(ax,real(gamma_YL),imag(gamma_YL),'bo','LineWidth',1.5)
hl1=legend(ax,{'ZL','YL'}, 'Location','bestoutside');title(hl1,'points')
Smith_plotRefLine2PhaseCircle(ax,ZL,Z0)
[x_circ1,y_circ1]=Smith_plotGammaCircle(ax,ZL,Z0);
[x_circ2,y_circ2]=Smith_plotRcircle(ax,Z0,Z0);
[x_target,y_target]=kreuzungen(x_circ1,y_circ1,x_circ2,y_circ2)
plot(ax,x_target(1),y_target(1),'ro','LineWidth',1.5)
plot(ax,x_target(2),y_target(2),'ro','LineWidth',1.5)

The function kreuzungen appended to these lines was developed by Douglas M. Schwarz dmschwarz=ieee*org, dmschwarz=urgrad*rochester*edu function available in this forum too.

4.- there are different custom toolboxes available in MATLAB file exchange. One that allows to set Z0 as input to a Smith chart related function of the tool set is

https://uk.mathworks.com/matlabcentral/fileexchange/22996-rf-utilities-v1-2

by Neil Tucker

The drawback of Tucker's is that his core function is named exactly as MATLAB RF toolbox smith, the problem being that while MATLAB’s smith does not take in Z0, MATLAB's smith only plots normalised impedances/admittances. When attempting to call Tucker's smith MATLAB returns zero, I got it working by renaming Tucker's smith function.

5.- Although encouraging Smith chart functions development with MATLAB, I am now learning KEYSIGHT ADS, and it's the right tool to solve RF circuits with Smith Chart plots.

http://www.keysight.com/en/pc-1475688/keysight-eesof-electronic-design-automation-EDA-software?nid=-34360.0&cc=GB&lc=eng

.

So, Taker if you find this answer useful would you please be so kind to mark my answer as Accepted Answer?

To any other reader, please if you find this answer of any help solving your question,

please click on the thumbs-up vote link,

thanks in advance

John BG

<mailto:jgb2012@sky.com jgb2012@sky.com>

EDIT: deleted Douglas Schwarz's copyright code.