Output Graphs

Output Section - Graphs
- Plot Using Filter Data
- Plot Using Coupling Matrix

Above the S-parameter display field two radio buttons are positioned.

Plot Using Filter Data - button

When this button is selected the displayed S-parameter curves reflect the filter data, which is entered in the Input Data section - i.e. N, f-center, BW, return loss, unloaded Q and transmission zeroes. The displayed curves will often be the design goal, which the filter designer is aiming at.

If one is only interested in the S-parameter characteristics, the topology matrix need not to be accurately defined.
In the Design Goal mode the displayed filter characteristics are not dependent of the topology matrix definition.

Plot Using Coupling Matrix - button

When the filter designer has achieved a satisfactory set of design goal characteristics, the topology matrix should finally be defined. The topology matrix defines the allowed coupling paths in the filter.

If a topology is defined, which can not fully implement the design goal characteristics, the synthesis error will become large (see error indicator). This would e.g. be the case if only main-line-couplings were allowed in the topology matrix, but one or more finite (i.e. different from 1e12 MHz) transmission zeroes were entered in the Input Data section.

The actually achieved filter characteristics can be inspected by selecting the "Plot Using Coupling Matrix" button.

When this button is selected the filter characteristics are calculated - and plotted - based on the synthesized coupling-matrix.
The "Plot Using Coupling Matrix" button therefore shows "what you get", where the "Plot Using Filter Data" button shows "what you want".

There will be no difference between the two display options if it is possible to synthesize the wanted filter characteristic within the defined topology.

Update

This button is intended for updating the S-parameter graphs when editing the coupling matrix values.