Harris Atlas DVL400, Technical Manual

Page: 119 / 180

2/25/03 888-2473-001 4-19
WARNING: Disconnect primary power prior to servicing.
Section 4 Theory of Operation
ATLAS Series™
Figure 4-4 Phase and Gain Board Block Diagram
4.4.4.2 Automatic Level Control (ALC)
Each PA module uses an Automatic Level Control or ALC circuit to keep the
module power output constant. The Module Controller receives an ALC control
signal from the Main Controller via the CAN bus. This signal is driven by the raise
and lower buttons on the control panel. A backup analogue ALC voltage is also sent
to each module via one of the parallel control lines. This analogue voltage will only
be used if CAN communications are lost. The forward power output of the module
is based on the factory calibration of the forward power sample from the pallet
combiner inside the module. The ALC circuit on the Phase and Gain board will
increase or decrease the drive level to the predriver to keep the module output
constant. However, if a pallet were to fail, the PA Module Controller will modify
the ALC algorithm so that the pallets are not over-driven and pre-correction
requirements do not change significantly.
RF
IN
Splitter
RF Mute
I
Attenuator
Q
Attenuator
I
Q
Control
Signal
Control
Signal
Hybrid
0
o
-90
o
In-Phase
Combiner
Driver
RF
RF Out
to
Pre-Driver
Envelope
RF Detector
Input Over-Drive
Comparator
Input Power
Sample Adjust
To
Module
Controller
I
Q
Output