Plot View

This page provides an overview about the different plot features in CST DESIGN STUDIO™.

A plot window will open once a 1D result is selected in the navigation tree.

When a tree item is selected, the plot toolbar shows possible visualizations of the result. Depending on the result type, only some of the following toolbar icons may be active:

	shows the real part of the result
	shows the imaginary part of the result
	shows the magnitude of the result
	shows the dB-scaled magnitude of the result
	shows the phase of the result
	shows the result in polar coordinates
	shows an admittance Smith Chart of the result
	shows an impedance Smith Chart of the result

Cartesian Plot

In a cartesian plot the 1D values are plotted in a cartesian system where the abscissa holds the function parameter and the ordinate holds the function value.

The plot is labeled according to the results it contains. The labels of the graphs can be found on the right side of the plot and they are of the same color and style as the graph they belong to.

$image\1dresplot.gif$

Polar Plot

In a polar plot, complex values can be represented. The abscissa holds the real parts and the ordinate holds the imaginary parts. In this plot, both the real and the imaginary values are functions of the independent parameter. Therefore, the parameter itself cannot be read explicitly.

In polar plots, the distance from the origin to the graph is the absolute value and the angle from the real axis is the phase of the complex variable.

$image\1drespolar.gif$

Smith Chart

The smith chart is very similar to the polar plot. It also plots complex values where the real and imaginary parts are functions of the independent parameter. The difference is that the axes are transformed from the ”reflection parameter space” into the ”impedance space.” That is, straight lines become circles and circles become straight lines.

Smith Charts are defined only for reflection parameters (S11, S22 etc). Therefore, only these values are plotted.

$image\1dressmith.gif$

Impedance Norm: The transformation from reflection coefficient to impedance values is made according to

$image\reflection2impedanceformula.gif$ .

This definition assumes a constant normalizing impedance. For this impedance, the line impedance is usually used.

However, for some structures (like wave guides with TE/TM modes) there is no reasonable definition for a line impedance. In these cases a Smith Chart is plotted anyway. The curve label will be modified to point out that the reference impedance is variable. It is clear that in this case the circles (and arcs) in the Smith Chart are not lines of constant real (or imaginary) part of the impedance. Nevertheless it's possible to access the corresponding complex impedance value of every reflection coefficient by placing a curve marker (explained below) on the curve.

If the scattering parameters are re-normalized by hand to an arbitrary value, the user-defined impedance will be taken as the normalizing impedance for the Smith Chart.

General Plot Features

The following general plot features are available:

Zoom and Pan

Holding down the left mouse button and dragging will zoom into the view.

Holding down the middle mouse button and dragging will pan the view.

Pressing space or selecting Reset View from the context menu will reset the view.

The current plot mode can be changed by selecting Zoom Mode or Pan Mode from the 1D plot context menu, which will define the view operation that is performed when holding down the left mouse button and dragging.

The zoom state of a tree item is remembered until the view is reset. Selecting a different item in the navigation tree will not destroy the zoom state of the currently selected tree item.

Curve Markers

Curve markers will display the current ordinate and abscissa value in an additional legend window. If View Add Curve Marker or Add Curve Marker in the context menu of an arbitrary 1D plot window is selected, the plot mode (zoom or pan) will be temporarily disabled. Now a curve marker can be set on a desired point of a result curve by a left double click on the corresponding location. After the double click the previous plot mode will be switched on again. This feature can also be accessed by pressing 'm' on the keyboard.

Double clicking on a curve marker will open an additional dialog. Here the marker can be moved to a specific value or it can be deleted. This dialog also allows setting multiple curve markers at the specified value to all the result curves of the current plot. It is possible to remove all curve markers of a plot by selecting View Remove All Curve Markers. It is also possible to remove a single curve marker by hovering the mouse cursor over the marker and pressing the 'delete' key on the keyboard.

Annotations

Annotations can be added to any desired result plot by selecting View Add Annotation... or Add Annotation... in the context menu of the plot window. This will open the Annotations Dialog. Annotations will be stored separately for every 1D plot.

Select Curves

Selecting a subset of the currently shown curves can be done using the Curve Selection Dialog.

Curve Style

The line style, line thickness and colors of the plotted curves can be changed using the Curve Style Dialog.

Plot Properties

The plot ranges of the plotted curves can be changed using the Plot Properties Dialog which can be found under 1D Plot Properties for cartesian plots and under Smith Chart and Polar Plot Properties for Smith Chart and Polar plots.

Cartesian Plot Features

The following special plot features are available for cartesian plots:

Axis markers

It is possible to enable an axis marker in any cartesian plot by selecting View Show Axis Marker or Show Axis Marker in the context menu of the plot window. All frequency (or time) dependent plots like S-Parameters and Balance share the same axis marker object. The axis marker has a legend that shows all values of intersection of the marker and the curves in the plot. Different features are available for the axis marker:

Axis Marker... : will open an additional dialog in which the axis marker can be moved to a specified abszissa value. This feature can also be accessed by pressing the 'tab' key or by double clicking on the axis marker.
Move Axis Marker to Minimum: moves the Axis Marker to the abszissa coordinate with the smallest ordinate. If some curves are highlighted by double clicking on the curves (or the corresponding legend labels), the marker will move to the minimum of the highlighted curves.
Move Axis Marker to Maximum: moves the Axis Marker to the abszissa coordinate with the largest ordinate. If some curves are highlighted by double clicking on the curves (or the corresponding legend labels), the marker will move to the maximum of the highlighted curves.

The following features can be accessed once an axis marker is enabled:

Bond Axis Marker Window: If the legend window of the axis marker was dragged to arbitrary location of the plot window this feature will attach it to the marker again. Double clicking on the axis marker legend window in the plot has the same effect.

Measure Lines

It is possible to enable measure lines in any cartesian plot by selecting View Show Measure Lines or Show Measure Lines in the context menu of the plot window. All frequency (or time) dependent plots like S-Parameters and Balance share the same measure lines object. It's possible to drag the measure lines to arbitrary locations in the plot domain which makes it easy to measure distances in the direction of the ordinate or the abscissa. Double clicking on one of the measure lines opens a dialog which allows specifiying the value of the measure line.