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
) 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 
and 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
and 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, and admittance in a Smith evaluation table window.
The available plot types for the Smith Plot Group are Reflection Graph, Impedance Graph, Admittance Graph, and Table Graph.
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Select a Data set. 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.
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If Stored output times is selected, the Times section is auto-filled with information from the selected Data set.
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For some Solution data sets, you can select the Load case to use in the plot group (if any load cases exist).
For some Solution data sets, select a Parameter selection (freq): All, First, Last, From list, or Manual.
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If Manual is selected, enter Parameter indices (1-91) (the actual indices depend on the number of solutions). Or click the Range button (
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The Title type is automatically generated by default (the Automatic option). Select Custom, Manual, or None as needed. See Plot Titles for Plot Groups and Plot Types 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).
Manually enter axis labels by selecting the x-axis label and y-axis label check boxes for 1D plot groups.
Select the Manual axis limits check box to edit the limits already assigned based on the data set. For 1D plot groups, this is for the x minimum, x maximum, y minimum, and y maximum. For Polar Plot Groups, this is for the r minimum and r maximum.
For the 1D Plot Group, and as needed, select the following check boxes: Preserve aspect ratio, x-axis log scale, and y-axis log scale. Select the Preserve aspect ratio check box to keep the distances on the x-axis and y-axis equal.
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Select the Impedance coordinates check box to create a grid for an impedance Smith plot.
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Select the Admittance coordinates check box to create a grid for an admittance Smith plot.
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Select the Show legends check box 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 check box 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 left, Middle right, Middle left, Lower right, 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 settingscheck box. 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 check box (selected by default) to use a common exponent at the end of each axis. Clear this check box 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 check box 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: 4) 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 check box 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.
) to add a plot window to the list of available windows.