The Smith Plot Group node () creates a graph for Smith plots, where electromagnetic properties are plotted on the complex reflection coefficient plane. Typically, the plotted values are the normalized reflection, impedance, or admittance. The complex-valued reflection coefficient Γ for an impedance ZL attached to a transmission line is defined as

where Z0 is the characteristic impedance. Physically, Γ must have an absolute value of at most 1, and it can therefore be plotted in the complex unit circle. The normalized input impedance zL is defined as

For a passive circuit (no gain), it holds that |Γ| ≤ 1and that Re(zL) ≥ 0. Thus the relation between Γ and zL defines a conformal mapping between the unit circle and the right half of the complex plane. An impedance Smith plot is the unit circle with grid lines for Re(zL) = constant and Im(zL) = constant for impedance coordinates. The admittance is defined as Y = 1/Z, and similarly you then have Y0 = 1/Z0 and yL = Y/Y0. Consequently,

is useful to display as an admittance Smith plot with grid lines for Re(zL) = constant and Im(zL) = constant for admittance coordinates.

You can click anywhere inside the perimeter of the Smith plot’s coordinates to get the numerical values for the reflection, impedance, or admittance in a Smith evaluation table window.

It is not possible to zoom or pan in a plot window that displays a Smith plot. In most respects, it otherwise behaves and have settings similar to a 1D Plot Group, with some differences according to the descriptions below for the available sections of the Settings window for a Smith Plot Group.

The available plot types for the Smith Plot Group are Reflection Graph, Impedance Graph, Admittance Graph, and Table Graph.

Select a Dataset. Depending on the type of data, also specify, for example, the time, frequency, or eigenvalue selection.

For Parametric Sweep studies, also select an option from the Select via list: Stored output times or Interpolated times.

For some Solution datasets, you can select the Load case to use in the plot group (if any load cases exist).

For some Solution datasets, select a Parameter selection (freq): All, First, Last, From list, or Manual.

If you have defined a compatible configuration (see Configurations), which is typically a Multiselect Solution, the you can choose From configuration from the Solution parameters list (the default is Manual). With From configuration, choose a compatible configuration from the Configuration list to use its settings for the solution parameters such as the time, eigenvalue, or parameter values to use.

This section is only available if at least one physics or multiphysics interface in the model includes a phase. See Phase Settings in Plots.

Select Save plot data to save the plot data in the model. This section only appears for the manual setting of the option for saving plot data. See Saving Plot Data in the Model.

The Title type is automatically generated by default (the Automatic option). Select Custom, Manual, Label, or None as needed. See Plot Titles for Plot Groups and Plots for more information.

From the Color list, choose Custom to define a custom color for the title, or choose one of the predefined colors (the default is Black).

From the Resolution list, select a resolution for the grid: Fine, Normal (the default), or Coarse.

If you have added Graph Plot Style configuration nodes (see Configurations), you can choose to use one for the plot style settings in the graph plot nodes under this plot group. To do so, choose it from the Configuration list. The plot style settings that are then taken from the configuration will be grayed out in the settings for the graph plot nodes in this plot group.

Select the Show legends checkbox to display legends for the quantities in the graph and, if using a Color Expression subnode, color legends. For color legends, select or clear the Show maximum and minimum values checkbox to show or hide those values from the top and bottom of the color legends. Specify the position of the graph legends for the plots in the plot group. From the Position list, select Upper right (the default), Upper middle, Upper left, Middle right, Center, Middle left, Lower right, Lower middle, or Lower left. Legends in all plots in the plot group use this position.

To override the automatic formatting of the numbers on the axes, select the Manual axis settings checkbox. Then adjust the formatting using the following settings:

From the Notation list, choose Automatic to let the program choose decimal notation or scientific notation (E-notation) depending on the values of the displayed numbers. Choose Scientific to only use scientific notation.

Select the Use common exponent checkbox (selected by default) to use a common exponent at the end of each axis. Clear this checkbox to instead display the full numbers, including the exponents, next to the corresponding axis tick. One of these formats may be better suited to display the axes if the plot window is small, for example.

Select the Show trailing exponent checkbox to display all numbers based on the precision used, including trailing zeros (for example, 5 is then displayed as 5.000 when the precision is set to 4).

In the Precision field, enter a positive integer (default: 5) for the numerical precision (number of digits displayed).

Select a Plot window. The Graphics window is the default, but any other plot window can be selected, or select New window to plot in a new window. Select the Window title checkbox to enter a custom title (except for the Graphics window), which is then available in the Plot window list for all models. Click the Add Plot Window button () to add a plot window to the list of available windows.