Defected Ground Structure - CST2013 MWS Examples

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General Description

In this example the scattering parameters of a simple microstrip line with an interrupted ground plane are calculated. (The image above displays this defected ground plane.)

Structure Generation

The general settings for this example are optimized for a planar microstrip coupler. The boundaries are set to magnetic type to prevent the excitation of auxiliary box modes.

Please note, that the Project Template Wizard guides you to easily setup specialized and predefined templates for certain application areas.

The entire structure is created by defining basic bricks and using the extrusion tool and the mirror operation. The holes in the ground plane are formed by subtracting several bricks from it.

The background (which is the calculation domain) is enlarged in both positive and negative z-directions in order to minimize the effect of the boundary conditions on the solutions.

Solver Setup

The microstrip line is terminated at both sides by waveguide ports which propagate the fields into and out of the structure. For this example only the fundamental mode needs to be considered. The excitation signal is a Gaussian shaped pulse referring to the frequency range from 0 to 10 GHz.

The symmetry of the structure is taken into account by using a magnetic symmetry condition. Since the structure is loss-free and has only two ports, the entire S-matrix can be obtained by just a single simulation run. The check for a loss-free two-port structure is activated by switching on Simulation: Solver Start Simulation Time Domain Solver Specials... General Consider two port reciprocity.

Post Processing

The S-Parameters are available in the folder 1D Results in the navigation tree. This folder contains also the evolution of the total field energy over the time and the energy balance of the S-Parameters.

The port modes and the result of the previously defined electric field monitor can be found in the 2D/3D Results folder.