In index-based segmented sweep the frequency segments may be in any order. This may be useful for particular test patterns where reverse sweeps are needed or particular frequencies must be measured before others due to DUT hysteresis. The setup menu and an example table are in Figure: Main Menu for Index-based Segmented Sweep—INDEX BASE SETUP Menu and Figure: Tableau Entry Table for Index-based Segmented Sweep.

All plotting in this sweep type is based on the point index, which is listed in the last column of the table below.

Aside from the increased flexibility in ordering, there are few other differences relative to frequency-based segmented sweep. One exception is that there is now no choice of graph mode; it will always be index-based. In this case, it is to avoid confusing and unreadable displays where one could have many reverse tracing operations.

It should be noted that there is a special form of segmented sweep available over the remote interface only (see the VectorStar Programming Manual—10410-00322 for more details). In this mode, a discrete list of frequencies (up to 25000 in the usual VNA operating mode) can be sent, in any order, and without segment definition. This gives considerably more flexibility in defining the frequency sweep without having to enter lengthy data through a graphical user interface. When this entry method is used, a single segment will appear in the segmented sweep table with a notation that it is a special list. The full list being used is available over the remote interface or with any of the text file save processes. This method sometimes is labeled ‘discrete fill’.