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Functional Description
2-5 ALC Loop Operation
MG362x1A MM
PN: 10370-10386 Rev. B
2-9
2-5
ALC Loop Operation
In the MG362x1A, a portion of the RF output is detected and coupled out of the directional coupler/level
detector as the feedback input to the ALC loop. The feedback signal from the detector is routed to the B5 ALC
Module where it is compared with a reference voltage that represents the desired RF power output level. If the
two voltages do not match, an error correction signal is fed to the modulator shaper amplifier circuits located
on the B5 Module. The resulting ALC control voltage output causes the level control circuits, located on the
A10 switched filter assembly, to adjust the RF output level. Thus, the feedback signal voltage from the level
detector will be set equal to the reference voltage.
The level reference DAC, under the control of the CPU, provides the RF level reference voltage. By setting
the output of this DAC to the appropriate voltage, the CPU adjusts the RF output power to the level selected
by the user.
External Leveling
In the external leveling mode, an external detector or power meter monitors the RF output level of the
MG362x1A instead of the internal level detector. The signal from the external detector or power meter goes to
the B5 ALC Module assembly from the rear panel input. The ALC controls the RF power output level as
previously described.
ALC Slope
During analog sweeps, a slope-vs-frequency signal, from the B4 Analog Instruction Module, is summed with
the level reference and detector inputs into the ALC loop. The Slope DAC, under the control of the CPU,
adjusts this ALC slope signal to compensate for an increasing or decreasing output power-vs-frequency
characteristic caused by the level detectors and (optional) step attenuator. In addition, the Slope DAC lets the
user adjust for the slope-vs-frequency characteristics of external components.
Power Sweep
In this mode, the CPU has the ALC step the RF output through a range of levels specified by the user. This
feature can be used in conjunction with the sweep mode to produce a set of identical frequency sweeps, each
with a different RF power output level.
Note
The instrument uses two internal level detection circuits. For frequencies < 2 GHz, the level detector
is part of the down converter. The signal from this detector is routed to the B5 ALC Module as the
Detector 0 input. For frequencies
2 GHz, the level detector is part of the main directional coupler.
The signal from this detector is routed to the B5 ALC Module as the Detector 1 input.
Содержание Rubidium MG362 1A Series
Страница 12: ...Contents 10 PN 10370 10386 Rev B MG362x1A MM ...
Страница 16: ...1 9 ESD Requirements General Information 1 4 PN 10370 10386 Rev B MG362x1A MM ...
Страница 30: ...2 6 RF Deck Assemblies Functional Description 2 14 PN 10370 10386 Rev B MG362x1A MM ...
Страница 66: ...3 11 FM and Phase Modulation Calibration Calibration 3 36 PN 10370 10386 Rev B MG362x1A MM ...
Страница 164: ...4 26 Pulse Modulation Tests with the 86100C Oscilloscope Performance Verification 4 98 PN 10370 10386 Rev B MG362x1A MM ...
Страница 292: ...B 5 Self Test Messages Instrument Messages B 8 PN 10370 10386 Rev B MG362x1A MM ...
Страница 293: ......