User's Manual

044-05077 Rev. A
4-2
Preamplifiers
Main amplifier
Error amplifier
Two feed-forward loops with phase-shift and gain controls
DC/DC power regulator
Alarm monitoring, control, and display panel
Figure 4-1. G3S-1900-80 Two-Module Amplifier System
The main amplifier employs class AB amplification for maximum efficiency. The error amplifier and
feed forward loops are employed to correct signal nonlinearities introduced by the class AB main
amplifier. The error amplifier operates in class AB mode. The RF input signals are amplified by a
preamp and coupled to an attenuator and phase shifter in the first feed-forward loop. The main
signal is phase shifted by 180 degrees and amplified in the premain amplifier. The output from the
premain amplifier is fed to the class AB main amplifier. The output from the main amplifier is
typically 100 watts. The signal is output to several couplers and a delay line.
The signal output from the main amplifier is sampled using a coupler, and the sample signal is
combined with the main input signal and input to the second feed-forward loop. The error signal is
attenuated, phase shifted 180 degrees, then fed to the error amplifier where it is amplified to a
level identical to the sampled output from the main amplifier. The output from the error amplifier is
then coupled back and added to the output from the main amplifier. The control loops continuously
make adjustments to cancel out any distortion in the final output signals.
RF IN J9 VVA COUPLER BPF
ALC_LED
MOD PORT
BDM PORT
RF OUT J2
J8
RS485/ADD.
RS485/RS232
RMS DET.
500-01451
J5/J6
J3/J4
INTERFACE
ASSY.
500-01468
POWER SPLITTER
FORM C ALARMS
J7
SIGNAL DISTRIBUTION
500-01467
17
17
ACTIVE POWER COMBINER
MCA 1
MCA 2
IN-RUSH
IN-RUSH
DC_CH1
DC_CH2
SPLITTER &
SIGNAL DIST.
ASSY.
500-01435
80A MAX
80A MAX
DB9
DB9
J1
DB9
2X3
2X3
2
12
4
COMBINER
ASSY
500-01434
5 5
CONTROL
ASSEMBLY
500-01105
100 30