HP 8360 User’s, A-6Operating and Programming Reference

Note	Two terms are used in the following discussions: power output and
	ALC level. Power output means actual output power including the
	effects of the attenuator. ALC level means power levels before the
	attenuator. In synthesizers without attenuators, these two terms are
	equivalent.
	Internal Leveling - Leveling Mode Noxrnal,
	L e v e l i n g P o i n t Intrnl
	In this configuration (Figure A-l), power is sensed by a detector
	internal to the synthesizer and a dc output from this detector is fed
	back to the Level Control Circuits.
	The ALC level is limited at the low end by the Level Control Circuits
	and at the high end by maximum available power. Noise and
	drift limit the range at the low end to -20 dBm or greater. The
	combination of RF frequency and RF components (different models
	of synthesizer have different RF components) limit the ALC range
	available at the high end. The internal instructions (firmware) of
	the synthesizer limit the ALC level range available for request from
	-20 to +25 dBm. If the power level requested is higher than the
	synthesizer is capable of producing, the maximum available power is
	produced, and the message line displays UNLVLED (unleveled). When
	the synthesizer performs frequency sweeps at certain ALC levels,
	maximum available power can be exceeded during small portions of
	the sweep; in this case, a flashing UNLVLED message appears.
	ALC leveling accuracy depends on power level. Although the ALC
	level is useable from -20 to +25 dBm, it is most accurate from
	-10 to +lO dBm. This fact is reflected in the performance
	specifications of the synthesizer.
	Coupled Operation. Since many applications require power output
	less than -20 dBm, an optional step attenuator has a range of
	0 to 90 dB, in 10 dB steps. With this option, power output down
	to -110 dBm is achieved when the Step Attenuator and Level
	Control Circuits work in conjunction (see Figure A-l). With the
	attenuator, the ALC level is normally used over the smaller, more
	accurate portion of its range. Since ALC level accuracy suffers below
	-10 dBm, and at some frequencies only $1 dBm of RF output is
	available, the ALC level is set between -10 and 0 dBm. For power
	less than -100 dBm, the attenuator is set to 90 dB, and the ALC
	level is used from -10 to -20 dBm. At frequencies where power
	output above 0 dBm is desired, the attenuator is set to 0 dB, and the
	ALC level is used from 0 to +25 dBm (or whatever power is available
	at the RF frequency in use).
	Coupled operation is assumed by the synthesizer unless
	Uncoupl Atten or Leveling Mode ALCoff is selected. The proper
	combination of ALC level’and attenuator setting is decided by the
	firmware. In coupled operation, when desired power output is set via

A-6 Operating and Programming Reference	HP 8360
User’s	Handbook