There are several limitations when applying the diagonal port feature.
- Once you select a reference plane as an individual reference plane any coupling between feedlines is no longer removed during the de-embedding process. Therefore, when using the diagonal port feature, care should be taken to place ports and their feedlines far enough apart that coupling effects are not significant. An example of the feedlines being too close to use diagonal ports is shown below.
- The em analysis cannot calculate the transmission line parameters Eeff, and Z0 for a diagonal port since the port is not separated from the feedlines when de-embedded. However, the resulting response data is still accurate.
- When using a diagonal reference plane, it is important to ensure that the two sides of an angled polygon are parallel to each other. The angle of the two polygon edges extending from the port are used to determine the angle of the reference plane. If the angles are different, the setting becomes ambiguous and the reference plane reverts to being orthogonal.
