The channel menu itself is fairly simple. While the system defaults to 1 channel (under a preset command), here a different number of channels may be selected. The active channel (indicated by a thick white border) may be selected by clicking on that channel’s window or it can be incremented using this menu (Chan. Next and Chan. Previous). The button Chan. Max can be used to force the active channel to occupy the entire data screen area. Note that the other defined channels will continue to sweep even when this mode is entered. The Chan. Max command is a toggle and can be undone by clicking it again. Chan. Max can also be accomplished by double-clicking the channel area away from a specific graph (that leads to Trace Max discussed later). These commands are illustrated in the top level menu shown in Figure: CHANNEL Menu.

Once a given number of channels is selected, the layout of those channels is selected in a submenu shown in Figure: CHAN. LAYOUT (CHANNEL LAYOUT) Menu. Note that selecting a layout with more channels will update the channel count since gaps in the sweep processing are not allowed. Because there are many combinations of channels possible, this window is quite lengthy (shown in two parts in Figure: CHAN. LAYOUT (CHANNEL LAYOUT) Menu).

 

The number of channels available first depends on the VNA maximum point setting which in turn depends on the VNA model number.

If multiple channels are available in the VNA, any number of channels can be configured between 1 and 16 channels.

Using the CHAN. LAYOUT menu shown in Figure: CHAN. LAYOUT (CHANNEL LAYOUT) Menu above, layouts are limited to values 1, 2, 3, 4, 6, 8, 9, 10, 12, or 16 channels.

Only those values corresponding to semi-symmetric layouts are allowed as suggested by the channel layout menu and other entries will be coerced.

Once the number of channels and the layout has been selected, it then remains to define each of the channels. The sweep control parameters apply to the active channel so one may cycle through the channels entering values as needed. Alternatively, the setups for a channel may be copied through the setup save/recall mechanism since setups can be saved on a per-channel basis. Note that save/recall can also be applied to all channels.

It has been discussed that most sweep-setup parameters are per-channel in nature. To clearly delineate when these apply, the per-channel functions include:

One additional behavior associated with channel count relates to the maximum number of points that may be defined in a sweep. Normally this limit is 25,000 pointsMS4640A Series VNAand this value can be used with any number of channels.

The VNA mode can be switched to a maximum of 100,000 points, but in this case, only one (1) channel is allowed. This mode is selected with the MAX. POINTS menu (shown below in Figure: MAX. POINTS (MAXIMUM POINTS) Menu) which is available at:

This selection itself is, of course, per-system since the selection determines the number of channels that will be available.

 

An example of a three-channel setup is shown in Figure: Typical Three-Channel Display. In this case, all three channels have different frequency ranges, the same IF bandwidth was used in each, and the first channel (at Figure: Typical Three-Channel Display – #1 on the top or Ch1) is active as indicated by the thick white border.

 

Generally, the sweeps for each channel are executed sequentially. That is, all of the sweeps for Channel 1 are performed first followed by all of those for Channel 2, and so on. Hold events and triggering events can be per-channel or per-system (and some subsets of the channel as well.) These menus are shown in Figure: HOLD FUNCTIONS Menu for hold events and Figure: MANUAL TRIGGER Menu for triggering events. The HOLD FUNCTIONS menu is available from the SWEEP SETUP menu.

Note that while triggering can be done per-point and per-port, it still refers to the setup of the channel and it is never reduced to measurements related to a trace. As these hold and trigger functions are used, the actual measurement sequence can, of course, change. The HOLD FUNCTIONS menu shown below to illustrate some per-system aspects (green dashed circle) of the hold function as opposed to the usual per-channel functions at the top of the menu (red circle).

The Manual Trigger menu is shown below to illustrate per-channel behavior (second button), per-portion-of-channel behavior (third and fourth buttons), and per-system behavior (first button). Other trigger modes have analogous behaviors.