Agilent Technologies 8360B, User Manual, Page: 157 / 496

4
ALC
5
Figure A-2. Typical External Lev eling Hookup
ALC Disabled -
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
Leveling Mode ALCoff ,
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
Leveling Mode Search
ALC O. In this conguration, the ALC is disabled, p o w er is
not sensed at an y p oint, and therefore the absolute p o w er lev el is
uncalibrated (see Figure A-1). Direct and separate con trol of the
RF mo dulator (p/o RF Comp onents ) and the attenuator is p ossible.
The sw ept signal generator's fron t panel indicates the attenuator
setting and a reference lev el. The reference lev el is an appro ximate
indication of the attenuation pro vided b y the RF mo dulator.
T ypically the RF amplier that follows the mo dulator is saturated
for mo dulation lev els near 0 dB. Therefore the actual c hange in the
RF output p o w er will not track the indicated reference lev el un til the
amplier is out of saturation.
The ALC o mo de is useful for applications that in v olv e pulse
mo dulation with extremely narrow pulses. If the pulse is narrow
enough, the ALC may b e unable to pro vide accurate lev eling due to
bandwidth limitations.
Searc h. Searc h mo de is similar to the ALC o mo de in that the
ALC is disabled in order to remov e bandwidth limitations. The
essen tial dierence is that, when searc h mo de is enabled, the sw ept
signal generator searc hes out the appropriate mo dulator lev el suc h
that the RF output p o w er after the ALC is disabled closely matches
the p o w er prior to searc h mo de b eing enabled. Sp ecically , when
searc h mo de is selected the sw ept signal generator follo ws this
sequence of steps:
1. All mo dulation is disabled and the ALC system is closed to
pro vide a calibrated reference p o w er.
2. The output p o w er is measured using the in ternal coupler/detector.
3. The ALC system is disabled (op ened).
A-8 Operating and Programming Reference