Plot specified circuit object parameters on Smith chart


hsm = smith(hnet,i,j)
[lineseries,hsm] = smith(h,parameter1,...,parametern,type)
[lineseries,hsm] = smith(h,'parameter1',...,'parametern', type,xparameter,xformat,'condition1',value1,..., 'conditionm',valuem, 'freq',freq,'pin',pin)


smith(hnet,i,j) plots the ( i, j)th parameter of hnet on a Smith® Chart. hnet is an RF Toolbox™ network parameter object. The inputs i and j are positive integers whose value is less than or equal to 2 for hybrid and hybrid-g parameter objects, or less than or equal to hnet.NumPorts for ABCD, S, Y, or Z-parameter objects.

hsm = smith(hnet,i,j) returns the line series handle used to create the plot, hsm.

[lineseries,hsm] = smith(h,parameter1,...,parametern,type) plots the network parameters parameter1, ..., parametern from the object h on a Smith chart. h is the handle of a circuit ( rfckt ) or data ( rfdata ) object that contains n-port network parameter data. type is a text value that specifies the type of Smith chart:

  • 'z' (default)

  • 'y'

  • 'zy'

Type listparam(h) to get a list of valid parameters for a circuit object h.


For all circuit objects except those that contain data from a data file, you must use the analyze method to perform a frequency domain analysis before calling smith.

[lineseries,hsm] = smith(h,'parameter1',...,'parametern', type,xparameter,xformat,'condition1',value1,..., 'conditionm',valuem, 'freq',freq,'pin',pin) plots the specified parameters at the specified operating conditions for the object h.

xparameter is the independent variable to use in plotting the specified parameters. Several xparameter values are available for all objects. When you import 2-port rfckt.amplifier, rfckt.mixer, or object specifications from a .p2d or .s2d file, you can also specify any operating conditions from the file that have numeric values, such as bias.

The following table shows the most commonly available parameters and the corresponding xparameter values. The default settings listed in the table are used if xparameter is not specified.

Parameter Namexparameter values
Pout, Phase, LS11, LS12, LS21, LS22Pin (default), Freq
S11, S12, S21, S22, NF, IIP3, OIP3, VSWRIn, VSWROut, GammaIn, GammaOut, FMIN, GammaOPT, RNFreq

xformat is the format to use for the specified xparameter. No xformat specification is needed when xparameter is an operating condition.

The following table shows the xformat values that are available for the xparameter values listed in the preceding table, along with the default settings that are used if xformat is not specified.

xparameter valuesxformat values
PindBm (default), mW, W, dBW

THz, GHz, MHz, KHz, Hz

By default, xformat is chosen to provide the best scaling for the given xparameter values.

AMMagnitude (decibels) (default), Magnitude (linear)

condition1,value1, ..., conditionm,valuem are the optional condition/value pairs at which to plot the specified parameters. These pairs are usually operating conditions from a .p2d or .s2d file. For some parameters, you can specify a set of frequency or input power values at which to plot the specified parameter.

For example:

  • When plotting large-signal S-parameters as a function of input power, you can specify frequency points of interest using condition/value pairs.

  • When plotting large-signal S-parameters as a function of frequency, you can specify input power levels of interest using condition/value pairs.

  • When plotting parameters as a function of an operating condition, you can specify both frequency and input power values using condition/value pairs.

freq is the optional frequency value, in hertz, at which to plot the specified parameters.

pin is the optional input power value, in dBm, at which to plot the specified parameters.

If h has multiple operating conditions, such as from a .p2d or .s2d file, the smith method operates as follows:

  • If you do not specify any operating conditions as arguments to the smith method, then the method plots the parameter values based on the currently selected operating condition.

  • If you specify one or more operating conditions, the smith method plots the parameter values based on those operating conditions.

  • When you use an operating condition for the xparameter input argument, the method plots the parameters for all operating condition values.


Use the smithplot function to plot network parameters that are not part of a circuit ( rfckt ) or data ( rfdata ) object, but are specified as vector data.

Changing Properties of the Plotted Lines

The smith method returns lineseries, a column vector of handles to lineseries objects, one handle per plotted line. Use the Line Properties function to change the properties of these lines.

Changing Properties of the Smith Chart

The smith method returns the handle hsm of the Smith chart. Use the properties listed below to change the properties of the chart itself.


smith creates the plot using the default property values of a Smith chart. Use set(hsm,'PropertyName1',PropertyValue1,...) to change the property values of the chart. Use get(hsm) to get the property values.

This table lists all properties you can specify for a Smith chart object along with units, valid values, and a descriptions of their use.

Property Name


Units, Values


Line color for a Z or Y Smith chart. For a ZY Smith chart, the Z line color.

ColorSpec. Default is [0.4 0.4 0.4] (dark gray).


Color of the line labels.

ColorSpec. Default is [0 0 0] (black).


Size of the line labels.

FontSize. Default is 10.


Visibility of the line labels.

'on' (default) or 'off'


Line spec for a Z or Y Smith chart. For a ZY Smith chart, the Z line spec.

LineSpec. Default is '-' (solid line).


Line width for a Z or Y Smith chart. For a ZY Smith chart, the Z line width.

Number of points. Default is 0.5.


The Y line color for a ZY Smith chart.

ColorSpec. Default is [0.8 0.8 0.8] (medium gray).


The Y line spec for a ZY Smith chart.

LineSpec. Default is ':' (dotted line).


The Y line width for a ZY Smith chart.

Number of points. Default is 0.5.


Type of Smith chart.

'z' (default), 'y', or 'zy'


Two-row matrix. Row 1 specifies the values of the constant resistance and reactance lines that appear on the chart. For the constant resistance/reactance lines, each element in Row 2 specifies the value of the constant reactance/resistance line at which the corresponding line specified in Row 1 ends.

2-by-n matrix. Default is [0.2000 0.5000 1.0000 2.0000 5.0000; 1.0000 2.0000 5.0000 5.0000 30.0000]


collapse all

Create an amplifier object from |default.s2p|.
amp = read(rfckt.amplifier,'default.s2p');

Plot S11 on the smith chart.


ans = 
  Line (S_{11}) with properties:

              Color: [0 0.4470 0.7410]
          LineStyle: '-'
          LineWidth: 0.5000
             Marker: 'none'
         MarkerSize: 6
    MarkerFaceColor: 'none'
              XData: [1x191 double]
              YData: [1x191 double]
              ZData: [1x0 double]

  Show all properties

Introduced before R2006a