Agilent Technologies 8935 Series, Manual

Page: 310 / 343

Chapter 10 309
Block Diagrams
RF Generator Section
Level Control
The A2A44 Output Section assembly ( Figure 10-19 on page 312 ) has an
automatic-level-control (ALC) loop that acts as a vernier control of RF
level between
−
2 and +9 dBm. A step attenuator in the A2A130 RF
Input/Output assembly takes the level down to
−
127 dBm (
−
137 dBm at
the RF IN/OUT connector) in 5 dB steps.
Assemblies that affect output level calibration have factory-generated
calibration data stored in the Test Set’s EEPROM. Calibration data is
fed to digital-to-analog-converters which control level-adjustable
devices in the RF path. These assemblies are:
• A2A200 100 W-Attenuator
• A2A130 RF Input/Output
• A2A24 Output Section
• A241 DC Block
Modulation
Amplitude modulation (AM) is done on the A2A24 Output Section
assembly. The modulating signal from the A2A44 Modulation
Distribution assembly is applied to the ALC loop’s control voltage.
IQ modulation is done on the A2A120 LO IF/IQ Modulator assembly.
The IQ signal from the A2A34 Data Buffer is modulated onto the RF
signal from the A2A25 Signal Generator Synthesizer assembly.