User Manual

System Components
Power Amplifier – RF Section
General Description
The Power Amplifier circuitry is primarily located in the rear R.F. compartment
that provides R.F. shielding for all of the higher power R.F. circuitry. The
basic configuration of the Power Amplifier RF Section is shown in Figure 6.
This configuration consists of a pre-amp module that drives an intermediate
stage amplifier (the driver stage) followed by the high power amplifier stage.
The high power stage consists of four separate transistors. The particular
transistor configuration is chosen to maximize the performance and reliability
of the products. All power transistors are mounted on special high thermal
performance board material and employ copper heat spreaders. The output
of the power transistor is fed into a low pass harmonic filter to eliminate
unwanted harmonics. The output of this harmonic filter also serves as the RF
output connector mount and support. The individual boards and preamp in
the power amplifier are all fused on an independent basis. This fuse board is
also located in the RF cavity in its own shielded compartment. Each fuse is
also instrumented with a LED indicator to provide easy visibility as to the
health and status of the fuse for that circuit. The back of the RF cavity
enclosure also serves as the mount for an auxiliary cooling fan.
FUSE BOARD
RF OUTPUT
HARMONIC
FILTER
HIGH POWER
AMPLIFIER SECTION
PRE-AMP &
DRIVER SECTION
RF INPUT
Figure 6 – Back View of the Power Amplifier
Version 3 3-10 07/18/01