The hierarchy of setups is illustrated in Figure: Setup Information Hierarchy. At the highest tier is per-system, these are variables that apply to all measurements on a given physical instrument. There are very few of these variables and they include:
• Step attenuator settings
• Bias tee on/off
• Certain portions of the hold system and certain triggering functionality
• AutoCal characterization files and cal kit files (are accessible from any channel)
These variables are often per-system to prevent a setup scenario that could significantly shorten the life span of the hardware. In the case of hold and triggering, it also allows an entire measurement suite to be somewhat more easily controlled externally. Others fall more in the category of utilities that are somewhat per-system in nature. The hierarchy of system, channel, and trace setup information is shown below. Generally, N (the channel count) may be up to 16 (except when more than 25,000 points in a sweep are needed) and M (the trace count) may always be up to 16.
Setup Information Hierarchy
Setup Hierarchy – System, then Channels, and then Traces
1 – Per System Settings – These settings affect the entire instrument such as the maximum number of measurement points as either 25,000 or 100,000.
2 – Per Channel Settings – If in 25,000 point mode, from 1 (one) to 16 channels can be configured. If in 100,000 point mode, only one channel is available.
3 – Per Trace Settings – Each configured channel can have from 1 to 16 traces. Each trace can be configured as a separate measurements, with separate markers, and a different display method. Each trace can have up to 12 total measurement markers and one (1) reference marker.
Per-Channel Variables
The second tier is that of the channel. As mentioned in the overview, the channel can almost be thought of as a separate virtual VNA. Although this term has been used differently in the past with other Anritsu VNAs, in the MS4640A Series VNA Series family, it includes a separate frequency list, separate calibrations and separate sweep control.
Per-Trace Variables
The third tier is that of the trace. As discussed above, this can be thought of as a data element (for example, S21 data for a given channel-based sweep setup). The per-trace flexibility mainly comes under the heading of post-processing and display.
Note
For historical reference, the 37xxxX family of Anritsu VNAs was limited to 1 channel and 4 traces. Although it may be somewhat confusing, in those instruments, what we now call traces were, then, called channels. This discrepancy was difficult to avoid when transferring to modern usage of the terminology.
