Standard workflow

Standard workflow means the cable schematic block can be used within all available simulation types that are provided by CST DESIGN STUDIO. As a prerequisite the equivalent circuit behind the schematic block must not have been prepared for a field solver coupling since this requires some constraints on the usage. Without these constraints the user can decide between two options how the cable model is interpreted during a circuit analysis task: standard or dispersive.

Circuit simulation aspects

The standard model (or non-dispersive model) interpretation inside the circuit simulator means the equivalent circuit of the cable will be completely integrated in the overall circuit. The type of the equivalent circuit, whether it consists of a pure lumped elements (RLC network) or it includes modal models (Modal models) either, decides which basic circuit elements are built into the electrical network. The advantage of this method is its flexibility concerning the usage in both frequency - or time-domain. One disadvantage is frequency dependent losses can only be approximated within a certain degree of accuracy (see Ohmic loss modeling or Dielectric loss modeling). In addition, the direct insertion of the equivalent circuit with its basic circuit elements may lead to large overall circuits and this can increase simulation times.

The dispersive model interpretation inside the circuit simulator means the equivalent circuit of the cable will not be directly integrated in the overall circuit. Instead of this, its frequency dependent behavior will be sampled on the terminals within a separate pre-precessing phase (from DC up to the specified Maximum valid frequency). In the actual circuit simulation only this frequency based terminal behavior will be considered. The most significant advantage of this method is its model order reduction. A further advantage is its possibility of using precise analytic formula to describe the frequency dependent losses, no approximation has to be made (see  Ohmic loss modeling or Dielectric loss modeling). A disadvantages of the method is the pre-processing step which can afford more time than the overall simulation with the standard model interpretation. In addition, this method should only be used if the number of terminals is low (a limit may be 10). Further on, the method should only be used within the frequency domain (AC- or S-Parameters task). For Transient tasks it may lead to less accurate results.

The following table shows the recommended usage of both methods:

In order to decide which model interpretation should be used, the user has to right mouse click on the schematic symbol and choose Properties from the pull-down menu. A dialog will appear where the tab Layout has to be selected: