Glenayre Document Number: 9110.01002
GL-T8541 PA
09/10/99
THEORY OF OPERATION
t8541
p6.
fdk
Copyright © 1997 Glenayre
Page: 6-1
6
THEORY OF OPERATION
6.1 General
This section contains a description of the individual pc assemblies, which comprise the RF
power amplifier chain. These boards are not designed to be repaired; instead, they are
replaced.
Refer to Figure 6-1, for a visual representation of RF flow through the GL-T8541 PA. Each
of the blocks of the block diagram represents a circuit board in the power amplifier module.
The PA module temperature, amplifier currents, forward output power level, and reflected
power levels are monitored by the metering board. The metering board is mounted on the
outside of the rear panel of the PA module, and is not shown in this diagram.
The 250 mW (25 +/-2 dBm) RF input is amplified to approximately 19 watts by the driver
board. The 19 watt driver board signal is applied to the 1 to 3 splitter board, which yields 6
watts from each of its three outputs. Each of the three power amplifier boards supplies 100
watts to the 3 to 1 combiner. The combiner board includes the 3 to 1 combiner, the low pass
filter, and the directional coupler; with losses of 0.35, 0.15, and 0.2 dB respectively. The
output of the combiner board (and therefore the power amplifier module) is shown at 250
watts. The amplifier module has enough headroom capacity in its output to allow for small
power calibration errors due to the typical variation of the RF wattmeters used in the field.
Figure 6-1 GL-T8541 PA Module RF Flow Block Diagram
250 W RF Output
to the Isolator
3-Way Power Combiner/
Low Pass Filter/l
Directional Coupler
3 Way
Power
Splitter
120 Watt
Push Pull
Amplifier
12 dB gain
Driver
250 mW (25 +/-2 dBm)
RF Input From
DSP Exciter
120 Watt
Push Pull
Amplifier
12 dB gain
120 Watt
Push Pull
Amplifier
12 dB gain
19 dB gain
0.2 dB loss
0.7 dB total loss
19 W
6 W
100 W
6 W
100 W
6 W
100 W
