Transient Solver Results Frequency Domain Solver Frequency Domain Solver Results Patch Antenna Array Antenna Array Calculation Geometric Construction Steps Combine Results Simultaneous Excitation Getting More Information
Geometric Constructions Introduction and Model Dimensions
In this tutorial you will learn how to simulate antenna devices. As a typical example you will analyze a circular patch antenna. The following explanations can be applied to other antennas as well.
Although, CST MICROWAVE STUDIO can provide a wide variety of results, this tutorial will concentrate mainly on the S-parameters and farfield results.
In addition, the single patch antenna will be extended to a rectangular 2x2 array pattern using three different methods. First, the farfield solution of the single patch antenna is applied to the antenna array feature, superimposing the results with different amplitudes and phase settings. Another possibility expands the patch model to a set of four identical antennas, each excitable with its own coaxial feed. Here, you have the option to calculate the antennas separately one after another and finally combine the results with arbitrary amplitudes and phase values, or to run the excitation simultaneously to produce the farfield result with only one solver cycle. The farfield distributions of all these possibilities will be compared.
We strongly suggest that you carefully read through the CST MICROWAVE STUDIO Getting Started manual before starting this tutorial.
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The structure depicted above consists of two different materials: The Substrate and the Perfect Electric Conductor (PEC). There is no need to model the air above because it will be added automatically (according to the current background material setting) when the open boundary conditions are specified. This will be done automatically with an appropriate template. The feeding of the patch is realized with a coaxial line.
Geometric Construction Steps
This tutorial will take you step-by-step through the construction of your model, and relevant screen shots will be provided so that you can double-check your entries along the way.
Please remember the Edit construction step.
? Select a Template
After you have started CST DESIGN ENVIRONMENT? and have chosen to create a new CST MICROWAVE STUDIOproject, you are requested to select a template that best fits your current device. Here, the Antenna (on Planar Substrate) template should be chosen. If the following dialog box does not occur automatically, select File
Select template... from the main menu.
?
Undo facility in the event that you want to cancel the last
This template automatically sets the units to mm and GHz, defines the background material to vacuum
and
selects
appropriate
boundary
conditions
(see
chapter
Boundary
Conditions). Because the background material has been set to vacuum, the structure can be modeled just as it appears on your desk.
? Set the Working Planes Properties
The next step will usually be to set the working plane properties to make the drawing plane large enough for your device. Because the structure has a maximum extension of 60 mm along a coordinate direction, the working plane size should be set to at least 100 mm. These settings can be changed in a dialog box that opens after selecting Edit the Getting Started manual.
Working Plane Properties from the
main menu. Please note that we will use the same document conventions here as introduced in
In this dialog box, you should set the Size to 100 (the unit which has previously been set to mm by the chosen template is displayed in the status bar), the Raster width to 2 and the Snap width to 0.01 to obtain a reasonably spaced grid. Please confirm these settings by pressing the OK button.
? Draw the Substrate Brick
The first construction step for modeling a planar structure is usually to define the substrate layer. This can be easily achieved by creating a brick made of the substrates material. Please activate the brick creation mode now (Objects
Tab key that will open the following dialog box:
Basic Shapes
Brick,
).
When you are prompted to define the first point, enter the coordinates numerically by pressing the
In this example, you should enter a substrate block that has an extension of 60 mm in each of the transversal directions. The transversal coordinates can thus be described by X = -30, Y = -30 for the first corner and X = 30, Y = 30 for the opposite corner, assuming that the brick is modeled symmetrically to the origin. Thus, please enter the first points coordinates X = -30 and Y = -30 in the dialog box and press the OK button.
Afterwards, you can repeat these steps for the second point:
1. Press the Tab key
2. Enter X = 30, Y = 30 in the dialog box and press OK.
Now you will be requested to enter the height of the brick. This can also be numerically specified by pressing the Tab key again; entering the Height of -0.7 and pressing the OK button (it is convenient to define the substrate in the negative z-direction). Now the following dialog box will appear, displaying a summary of your previous input:
Please check all these settings carefully. If you encounter any mistakes, please change the value in the corresponding entry field.
You should now assign a meaningful name to the brick by entering e.g. substrate in the Name field, keep the Component default setting (component1).
Please note: The use of different components allows you to combine several solids into specific groups, independent of their material behavior. However, in this tutorial, it is convenient to construct the single patch antenna as a representation of one component that can then easily be extended into a patch antenna array.
Finally, you need to define the substrate material. Because no material has yet been defined for the substrate, you should open the New Material Parameters dialog box by selecting [New Material...] from the Material dropdown list: