CST2013 MWS Examples: Three Line Taper (Single-Ended)

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General Description

In this example the single-ended S-parameter calculation of a three line taper is presented. The device consists of two single-ended ports with three inner conductors each. Two adjacent conductors are so close to each other that this multipin definition would lead to non-orthogonal modes in case of a normal multipin port. Therefore it is advisable to use single-ended ports which is demonstrated here. The conductors are located on a substrate and are tapered towards their ends which changes their mutual coupling over the structure length.

Structure Generation

The strip line ends as well as the substrate are modeled by defining basic bricks, for the creation of the strip lines itself the extrude feature is used. Many parts are mirrored due to the symmetry of the structure.

The metallic ground plane of the device is represented by the electric boundary condition. Some outer space is added above the structure by defining a surrounding background material.

Solver Setup

The three microstrip lines are terminated by two single-ended waveguide ports which propagate the fields into and out of the structure. The excitation signal is a Gaussian shaped pulse referring to the frequency range from 0 to 8 GHz.

Due to the relatively small permittivity of the substrate the mode field patterns hardly change at all over frequency so that the inhomogeneous port accuracy enhancement does not have to be used here. The single-ended S-Parameters are obtained using a fixed reference impedance of 50 Ohms.

Post Processing

The S-Parameters are available in the folder 1D Results in the navigation tree. Also the development of the total field energy through time as well as the energy balance of the S-Parameters can be found there. The port modes used in the transient calculation can be visualized in the folder 2D/3D Results. Please be aware that the modes in single-ended ports do not correspond to the shown multipin definition, therefore you find two different folders Port Modes (simulated modes, which also correspond to any field monitors) and Port Modes Single-ended (single-ended modes, which correspond to the single-ended S-Parameters).