ALC/AM/Pulse
Modulation This circuit subsystem consists of the A6 Pulse Gen-
erator PCB, the A9 PIN Control PCB, the A10 ALC
PCB, and the A14 SDM, SQM Driver PCB. It pro-
vides the following:
Level control of the RF output power.
AM and pulse modulation of the RF output.
Current drive signals to the PIN switches lo-
cated in the Switched Filter assembly and
Switched Doubler Module (SDM).
Bias voltages for the SDM and Source Quadru-
pler Module (SQM).
Drive signals for the optional Step Attenuator.
The CPU controls the A9 Pin Control PCB and the
A10 ALC PCB via the dedicated data and address
bus. It sends control data to the A6 Pulse Generator
PCB via the A16 PCB as serial data words. Refer to
paragraph 2-4 for a functional overview of the ALC
and modulation subsystem.
RF Deck This subsystem contains those elements related to
the generation, modulation, and control of the
sweep- and CW-frequencyRF signals. These ele-
ments include; the 2 to 20 GHz YIG-tuned oscillator,
the 0.01 to 2 GHz (0.5 to 2.2 GHz) Down Converter
assembly,the Switched Filter assembly, the
Switched Doubler Module (SDM), the Source Quad-
rupler Module (SQM), the Directional Coupler/Level
Detector,and the optional 110 dB (90 dB) Step
Attenuator.Refer to paragraph 2-5 for a functional
overview of the RF deck subsystem.
Power Supply The power supply subsystem consists of the A15
Regulator PCB, the A18 Power Supply PCB, the
A19 Line Conditioner PCB, and part of the A21
Rear Panel PCB and Rear Casting Assembly.It sup-
plies all the regulated DC voltages used by the sig-
nal generator circuits. The voltages are routed
throughout the instrument via the A20 Mother-
board PCB.
Inputs/
Outputs The A21-1 BNC/AUX I/O Connector PCB and the
A16 CPU Interface PCB contain the interface cir-
cuitry for the majority of the rear panel input and
output connectors, including the AUX I/O connector.
The front panel AM and External ALC inputs are
routed via the A20 Motherboard PCB to the A10
ALC PCB. The front panel FM and Pulse Trigger
2-8 682XXB/683XXB MM
FUNCTIONAL 682XXB/683XXB
DESCRIPTION MAJOR SUBSYSTEMS