User`s guide

Agilent E6432A Microwave Synthesizer User’s Guide 3-27
Soft Front Panel Help
ALC System Diagram
External Leveling Point
External Leveling Point (Ext Lvl), available from the Soft Front Panel,
controls which detector is used in the ALC loop. Selecting External
Leveling Point specifies that the EXTERNAL_DETECTOR_1 be used
which allows the synthesizer to level power by accepting an external
feedback connection from a negative-output diode detector. The Ext
ALC BNC connector on the front panel is used for the required signal.
Factory Preset Value: INTERNAL_DETECTOR
In externally leveled operations, the output power from the synthesizer
is detected by an external sensor. The output of this detector is returned
to the leveling circuits, and the output power is automatically adjusted
to keep the power constant at the point of detection. The following
figure shows a basic external leveling arrangement. The output of the
detected arm of the splitter or coupler is held constant. If the splitter
response is flat, the output of the other arm is also constant. This
arrangement offers superior flatness over internal leveling, especially if
long cables are involved.
In some instances, the use of an external detector and long cabling
creates excessive phase shift, which in turn could result in oscillations.
Problems such as this can be eliminated in External Leveling Mode by
selecting low ALC bandwidth.