Option 32 was covered somewhat in IMDView™ (Option 44) of this guide on IMD and elsewhere but it has uses for other measurements and definitely affects RF power distribution so the salient points will be revisited here.
As discussed previously, Option 32 is only available with dual source systems (Option 31) and provides a means for coupling second source power onto the primary source signal coming out Port 1. This is done with a switch and coupler arrangement shown schematically in Figure: Schematic of Option 32 Switch and Coupling Components (in reality, there are separate switches and couplers for above and below 2.5 GHz which is not shown here).
The switch/combiner are placed after their respective source loops when those options are installed (Option 51/61/62) so per-tone amplifiers/pads can be inserted in the source loops and they will not be exposed to the combined signal in IMD applications. For the multiple source case, this switch activation is done from the Other Setup | Power Setup submenu under the Power menu as shown in Figure: Power and Power Setup Menus: Option 32 Source 2 Out Redirection Control
Note
The Source Out Redirection button will not be available if in IMD mode. The source selection in that case must be made from the IMD configuration dialog.
Schematic of Option 32 Switch and Coupling Components
Power and Power Setup Menus: Option 32 Source 2 Out Redirection Control
The obvious signal combining application is two-tone Intermodulation Distortion which was covered in IMDView™ (Option 44). There are times when a manual IMD measurement must be orchestrated using multiple source control (e.g., a complex frequency conversion path with multiple multiplications/divisions and multiple frequency offsets) but the approach would be the same. There may be other complex test setups where Source 1 is used through its access loop and it is desired to drive Port 1 with Source 2 as suggested by Figure: Application Example for Option 32 and the Option 32 switching can be used to accommodate this configuration.
Because of the coupling and switch loss, the available power from Source 2 out Port 1 is reduced relative to that out Port 2 (by ~15 dB above 2.5 GHz and ~20–23 dB below 2.5 GHz with the difference being due to different combining structures). The isolation of the combining structures exceeds 20 dB which helps reduce source-to-source intermodulation residuals.
Application Example for Option 32
An application example for Option 32 is shown here where src 2 out Port 1 is used more for redirection than for signal combining and may be suitable for certain complex switched test setups.
Because of the power difference in Src2->P1 (as it is labeled in parts of the user interface), user power calibrations are commonly desired although there is a factory ALC calibration to account for those path differences in this mode to first order. When the redirection switch is activated, whether within IMD or not, a third choice appears on the power calibration selection as shown in Figure: Source 2 out Port 1 Selection Dialog. The power calibrations work the same as with the regular configurations but keep in mind the loss levels when selecting the Target Power. If too high a target is set, the power calibration will likely fail or will pass with a rather high error (should normally be << 1 dB).
Source 2 out Port 1 Selection Dialog
Access to the user power calibrations for the Src2->P1 path is provided by the power calibration selection button which opens the Select Port dialog. The redirection switch must be ‘ON’ for this extra choice to be available.
The Source 2–>P1 path is not useful in broadband mmWave modes as the routing to the multipliers is different and one would not normally want to combine signals prior to multiplication anyway (as the residual intermodulation products will be, by definition, extremely high). For mmWave applications, an external combiner instead of Option 32 is recommended (contact the factory for details).
