Microstrip Coupler - CST2013 MWS Examples

下载CST设计文件

General Description

In this example the S-parameter calculation of a directional strip line coupler is presented. The simulation is performed using waveguide ports.

Adaptive energy based meshing is applied to ensure that the obtained results are accurate regarding a certain accuracy level.

Structure Generation

The background material is defined as vacuum, the units are changed to millimeters, gigahertz and nanoseconds, and the boundary conditions are set to "electric". Furthermore, the mesh settings are changed to account for the planar microstrip structure.

During the construction of the model, the working coordinate system is used to define objects relative to each other. The structure is modelled by defining bricks as the strip line and the substrate. The bends are created as a solid of rotation defined by the microstrip's front face, an axis placed at the center of the circular path described by the bend, and the angle, which equals ninety degrees.

After adding both parts of the microstrip line, its new front face is extruded up to the center of the substrate. With the working coordinate system placed at the center of the substrate's top face, the first quarter of the microstrip lines is mirrored, copied and combined twice.

Solver Setup

The frequency range's upper and lower limit are set to 0.8 GHz and 1 GHz, respectively.

Three monitors are defined in order to examine the electric field, the magnetic field, and the power flow at 0.9 GHz. Four waveguide ports are created at each end of the strip line to perform the S-parameter calculation.

The excitation signal is a sine modulated Gaussian shaped pulse. Because of the symmetry of the structure all reflection coefficients will be identical as well as several transmission coefficients. These S-Parameter symmetries are utilized such that only one simulation has to be performed in order to get the entire S-Matrix.

Post Processing

The calculated port modes of the waveguide ports can be examined in the folder 2D/3D Results, while the results of the mesh adaption are added to the folder 1D Results Adaptive Meshing. The deviation of the scattering parameters in the last mesh adaption pass complies with the desired accuracy.

The S-parameter are accessible via the folder 1D Results. The monitors at 0.9 GHz illustrate the directional coupling of the device.