The key concepts to setting up multiple source control are:

For MS464A Series VNAs, up to four (4) external sources can be configured.

The frequency plan is separated into “bands”. There may be as many as 50 or as few as one. One needs multiple bands ONLY if the relationship between sources and the receiver change in an unusual way at some point in the sweep. Examples:

All source frequencies (internal or external) and the receiver frequency must be linearly related. All are expressed as linear equations as a function of a runner variable “f”. This variable f is always the one displayed on the X-Axis although it need not represent an actual frequency (although for convenience it usually does).

These linear relationships can change in different “bands” that the user defines. The band edges are always in terms of the runner variable f.

The band start and stop frequencies are in terms of the runner variable f. Thus they may or may not be physical. To reiterate, the choice is usually based on what one wants the X-Axis of the plots to be labeled in terms of (e.g., in terms of the RF frequency or in terms of the IF frequency for a mixer measurement).

 

The main multiple source setup menu is shown below in Figure: Main MULTIPLE SOURCE Setup Menu. The top half of the menu, pertaining to equation editing, will be dealt with first. The special functions of the lower half of the menu will be discussed later.

The top button on the menu toggles Multiple Source mode on or off, similar to the mode selection buttons on the APPLICATION menu (turning Multiple Source mode off here will change the mode on the APPLICATION menu to Standard). When this menu is entered, the MULTIPLE SOURCE tableau will appear in the lower part of the screen (Figure: MULTIPLE SOURCE Tableau below).

When the MULTIPLE SOURCE tableau first appears, the first band is in the table. The Add Band, Delete Band, and Clear Band buttons will have the obvious effects.

 

A red exclamation point (!) in the first column of the table indicates that an error is detected.

For each band, the following must be defined:

Each equation is of the following form:

Using the multiplier (M) and divisor (D), a rational relationship can be created between the desired frequencies. The offset (OS) completes the remainder of the linear relationship and is the CW frequency when the source is set to CW ON. Any of these parameters may be negative as long as the result of the equation is a valid frequency for that source (or receiver). This can be used for a reverse sweep (in certain mixer measurements for example).

When a cell is highlighted in the table (with the mouse or touch screen), the text entry box becomes active. Text can be directly entered into the table by double-clicking on the cell. The entry must be typed with a space between the number and the frequency units.

When a second band is added, the table adds another block as shown in Figure: MULTIPLE SOURCE Tableau – Two Band Multiple Source Tableau. Note that the bands must be contiguous although the sweep range need not be (by using segmented sweep for example).

 

As soon as values are changed in the table, the Done Editing button shown in Figure: Main MULTIPLE SOURCE Setup Menu becomes active. Selecting the Done Editing button will start an error check of all entered parameters. An error dialog may appear if an error is found. During the error checking, the system applies the band limit frequencies to each equation and checks that the results are valid for a given source or the receiver. If an external source is inactive, the error checking will not be performed for that line.

The EXTERNAL MODULE dialog box is accessed off the primary MULTIPLE SOURCE menu.

This dialog box allows the use of a 3738x or 3739x Test Set and external broadband or millimeter-wave modules. The activation is by band and when turned on, the test set will be informed to activate its modules and use current knowledge of the driving port. This would commonly be used for broadband or mm-Wave measurements when the broadband/mm-Wave mode is too restrictive for the desired measurements. This may happen if different IFs are desired, additional frequency converters are involved in the measurement, or other unusual scenarios. The external IF ports are automatically activated in any of the non-Off modes as are leveling and power control schemes associated with the given test set (see Broadband / mm-Wave Measurements (Option 007) for more test set information). Only one global mode can be selected per channel but that external module selection can be activated or de-activated on a band-by-band basis.

External mm-wave or broadband test sets are not being used. The dialog in this state is shown in Figure: The external module control dialog box with off selected is shown here.. The 3739x test set does not require external synthesizers, so these non-OFF choices will always be available assuming option 08x is present. The 3738 test set does not require additional options, but does require the presence of external synthesizers 1 and 2 on the GPIB bus.

The 3738x test set is being used with conventional OEM mm-wave modules (the ME7828 family of systems). In this case, a check box will be available per-defined band to allow activation of the test set in that band. This option is only available if External Sources 1 and 2 are connected and active. There are no other parameters to select other than to activate or de-activate on a band-by-band basis.

As an example to show how this selection might be used, consider a DUT that is a downconverter taking 250 to 300 GHz down to a fixed IF of 1 GHz. The LO is sub-harmonically driven with an effective multiplier of 18 and will be driven from External Source 3 (EXT. SRC 3). The RF is supplied by an external mm-wave module (WR-03 waveguide in this case), which also has an effective source multiplier of 18, and this will be driven from External Source 1 (EXT. SRC. 1). This external module also has an LO input (x20 effective multiplier) that will be driven from External Source 2 (EXT SRC 2). It is desired to measure both return loss (at the RF) of the DUT as well as its conversion loss. This will require two different multiple source setups since the conversion paths in the VNA are different.

Connect all external synthesizers and make sure the GPIB addresses match, and that 10 MHz clocks are synchronized (or higher frequency references if those are being used). It is desired that the DUT LO port be driven since that can affect return loss. Since the mm-wave module IF outputs will be used (and routed to the VNA rear panel), the Ext Module Ctrl for BB/mm-Wave must be enabled.

In this case, Ext Module Ctrl must be OFF since we will not be using the rear panel IFs. Note that this also disables the test set so some care is required with RF signal cabling.

The mm-wave (3739) selection also assumes the use of OEM mm-wave modules, but with the 3739x test set. Details on some applicable modules, from a hardware perspective, are discussed in Broadband / mm-Wave Measurements (Option 007). Any multiplied transceivers can be used here as long as the frequency and power plans are consistent with the VectorStar system with the 3739x test set. The test set offers additional power control options and assumes the use of the internal VNA sources so there are some additional selection options as suggested by Figure: The external module control dialog is shown as configured for a single active band of mm-wave (3739)..

The selection choices per band are described below:

For use with 374x and MA25300A modular components. This right side of the radio button array is for the broadband operation and for banded operation. The selection for BB/mmWave is straightforward. When checked in a given band, the test set will be activated, the VNA’s internal transfer switch will be shut down, and the rear panel IF ports on the VNA will be activated. There are at least three choices: broadband, E-band, or W-band. The distinction between these selections is based on the imposed frequency range limits when activated. Broadband allows from the lower instrument limit up to the upper limit of the system (125 GHz or 145 GHz (150 GHz operational) for ME7838A, and ME7838D systems respectively), E band allows 56-95 GHz (under range to 54.000000001 GHz allowed), and W band allows 65 GHz to 110 GHz. For systems loaded with option 080/081, two broadband buttons will be available for 125 GHz or 145 GHz (operational to 150 GHz) situations. The former should be used if 3743x modules are employed and either can be used if MA25300A modules are in use. The dialog in the case of broadband set for two bands is shown in Figure: The external module control set for broadband (3739x-based) mode is shown here with two bands configured for that mode..

These MA25300A, 3743x, and 3744x modules have independent source and receiver paths that can be selected from the above dialog. The selections can be interpreted as follows:

Figure: EXTERNAL MODULE CTRL Dialog Box Variants – OFF, mm-Wave 3738, and mm-Wave 3739 shows the EXTERNAL MODULE CTRL dialog box variants for OFF, mm-Wave 3738, and mm-Wave 3739. In Figure: EXTERNAL MODULE CTRL Dialog Box – Broadband, E-Band, and W-Band, the variants are shown for Broadband, E-Band 56 GHz to 95 GHz, and W-Band 65 GHz to 110 GHz.

 

The module block diagram below in Figure: 3743X Millimeter-Wave Module – Block Diagram of Leveling Options below illustrates where different leveling detection points are located.

 

Some of these choices can be made clearer with the following measurement examples.