ALC/
Modulation
This circuit subsystem consists of the A6 Square
Wave Generator PCB, the A9 PIN Control PCB, the
A10 ALC PCB, and part of the A14 YIG, SDM, SQM
Driver PCB. It provides the following:
q
Level control of the RF output power.
q
In the 691XXB, AM modulation and square
wave modulation.
q
Current drive signals to the PIN switches
located in the Switched Filter assembly and
Switched Doubler Module (SDM).
q
Drive signals for the Step Attenuator (Option
2) and the Diplexers (used with Option 22).
The A17 CPU controls the A9 Pin Control PCB, the
A10 ALC PCB, and the A14 YIG, SDM, SQM Driver
PCB via the dedicated data and address bus. It
sends control data to the A6 Square Wave 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-frequency RF signals. These ele-
ments include; the YIG-tuned oscillator, the 0.01 to
2 GHz Down Converter assembly, the optional 0.01
to 2.2 GHz Digital Down Converter assembly, the
Switched Filter assembly, the Switched Doubler
Module (SDM), the Source Quadrupler Module
(SQM), the Diplexer, the Directional Coupler/Level
Detector, and the optional 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
supplies all the regulated DC voltages used by the
690XXB/691XXB circuits. The voltages are routed
throughout the instrument via the A20 Mother-
board PCB.
Inputs/
Outputs
The A21-1/A21-2 BNC/AUX I/O Connector PCB and
the A16 CPU Interface PCB contain the interface
circuits for the majority of the rear panel input and
output connectors, including the
AUX I/O
connector.
2-8
690XXB/691XXB MM
FUNCTIONAL
690XXB/691XXB
DESCRIPTION
MAJOR SUBSYSTEMS
Summary of Contents for 680 C Series
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