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Plot measurement data on a Smith chart


smithplot(data) creates a Smith chart based on the input data specified in data.


  • A Smith chart is commonly used to display the relationship between a reflection coefficient, typically S11 or S22, and a normalized impedance.

  • The smithplot function replaces the smithchart function. (since R2023b)

smithplot(frequency,data) creates a Smith chart based on frequency and data values.

smithplot(ax,___) creates a Smith chart with a user defined axes handle, ax, instead of the current axes handle. Axes handles are not supported for network parameter objects. This parameter can be used with either of the two previous syntaxes.


smithplot(hnet) plots all the network parameter objects in hnet.


smithplot(hnet,i,j) plots the (i,j)th parameter of hnet. hnet can be a network parameter, an rfckt, an rfdata,or an nport object.

smithplot(hnet,[i1,j1;i2,j2;....,in,jn]) plots multiple parameters (i1, j1, i2, j2, …, in, jn) of hnet. hnet can be a network parameter, an rfckt, an rfdata, or an nport object.

smithplot(rfbudgetobj,i,i) plots the reflection coefficient of an rfbudget object.


For rfbudget objects, smith plot is restricted to reflection coefficients.

s = smithplot(___) returns a Smith chart object handle so you can customize the plot and add measurements.

s = smithplot('gco') returns a Smith chart object handle of the current plot. This syntax is useful when the function handle, p was not returned or retained.

smithplot(___,Name,Value) creates a Smith chart with additional properties specified by one or more name-value pair arguments. Name is the property name and Value is the corresponding property value. You can specify several name-value pair arguments in any order as Name1, Value1, ..., NameN, ValueN. Properties not specified retain their default values.

For list of properties, see SmithPlot Properties.


The property 'Parent' might be used to control the location where Smith chart gets plotted. Target can be figure, UI figure, UI panel, etc.


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Use the Smith plot interactive menu to change grid type of the Smith plot.

Plot the Smith plot of S-parameters data file, default.s2p.

data = nport('default.s2p');

Right click on the S11 line to reveal interactive menu, DISPLAY. Use Grid to change the grid to YZ on the Smith plot.


YZ- grid Smith plot is displayed below.


Plot the Smith plot of S11 of s-parameter data file using an impedance of 75 ohms.

data = sparameters('passive.s2p' );
s = sparameters(data,75);
p = smithplot(s,1,1, 'GridType','ZY');

Use the data cursor icon in the toolbar to insert a cursor on your smith plot chart. You now know the S11, VSWR, Impedance, and frequency values at that cursor. For admittance value, change the Grid Type.

Plot the Smith chart of an rfckt.amplifier object.

S = read(rfckt.amplifier,'passive.s2p');
ports = [1,1;1,2];
s = smithplot(S,ports); 
s.LineStyle = {'--', '-'}; 

This example shows how to plot impedance data on a smithplot

Define impedance data

z1 = 0.1*50 + 1j*(0:2:50);
z2 = (0:2:50) - 0.6*50j;

Characteristic Impedance

z0 = 50;

Convert impedance data to reflection coefficient

gamma1 = z2gamma(z1,z0);
gamma2 = z2gamma(z2,z0);

Plot the impedance data on the smithplot

s = smithplot(gamma1,'Color',[0.2 0 1],'GridType',"Z");
hold on;
s = smithplot(gamma2,'Color','g','LineStyle','-.','LineWidth',1);
s.Marker = {'+','s'}

s = 
  smithplot with properties:

         Data: {[26x1 double]  [26x1 double]}
    Frequency: {[]  []}

   Show all properties, methods

Read the S-parameter data.

amp = read(rfckt.amplifier,'default.s2p');
Sa = sparameters(amp);

Convert the S-parameter data to Y-parameter and plot it on a Smith plot.

Ya = yparameters(Sa);

Add Z-parameter data to the same plot.

Za = zparameters(Sa);
Z12 = rfparam(Za,1,2);
Freq = Za.Frequencies;
s = smithplot('gco');
add(s, Freq, Z12);

Input Arguments

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Input data, specified as a complex vector or complex matrix.

For a matrix D, the columns of D are independent data sets. For N-by-D arrays, dimensions 2 and greater are independent data sets.

Data Types: double
Complex Number Support: Yes

Frequency data, specified as a real vector.

Data Types: double

Input objects, specified as one of the following:

Data Types: object

RF budget object, specified as a rfbudget object.

Output Arguments

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Smith chart object handle. You can use the handle to customize the plot and add measurements using MATLAB® commands.


  • To list all the property Name,Value pairs in smithplot, use details(s). You can use the properties to extract any data from the Smith chart. For example, s = smithplot(data,'GridType','Z') displays the impedance data grid from the Smith chart.

  • For a list of properties of smithplot, see SmithPlot Properties.

  • You can use the smithplot interactive menu to change the line and marker styles.

Version History

Introduced in R2017b

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See Also