Par Mtr Range

Specifies the operating range of

an

 

external power meter used in an

 

 

external leveling setup. This causes

 

the

synthesizer display to

agree

with

 

the

power meter’s power

indication.

The following paragraphs explain the power control (leveling) function of the synthesizer in detail.

ALC SYSTEM - OVERVIEW

The ALC system, referred to as a system because it encompasses more than one functional area, is shown as a simplified block diagram in Figure A-l. The purpose of this system is to control the amplitude or power level of the RF energy generated by the synthesizer. It is a feedback control system, in which the output power is measured and compared to the desired power level. If the output power does not equal the desired power level the ALC system changes the output until they are equal.

Desired power level can be set by either front panel or remote operation. As shown in Figure A-l, the inputs and calibration data are processed by the synthesizer CPU, which uses this information to set the Level DAC.

In turn, the Level DAC sends a controlling voltage to the Level Control Circuits. In the presence of modulation, voltages appearing at the AM and/or PULSE inputs contribute to the control of the

Level Control Circuits.

In synthesizers with optional step attenuators, the power level at the output connector can be reduced by a maximum of 90 dB, in 10 dB steps. This is in addition to the control capabilities provided by the

Level Control Circuits.

A Feedback Signal to the Level Control Circuits can be provided by either internal or external detectors. This signal is the comparison voltage necessary for accurate, stable, power level settings and good source match at various Leveling Points. Alternatively, the power level can be set without using feedback. In this mode however, power level is uncalibrated and is subject to drift with temperature.

The following paragraphs describe the operation of the different leveling modes and leveling points.

A-4 Operating and Programming Reference

HP 8360

 

User’s Handbook