User's Manual

12 68P80801E35-A 9/1/2001
Power Amplifier (PA) EBTS System Manual - Vol 2
PA Theory of Operation
In the 40W PA, the amplified signals are then combined on the LFM and sent
directly to the RF Interconnect Board. In the 70W PA, the amplified signals are
then combined on the LFM and sent directly to the Combiner Board.
See Table 2 for the approximate total summed output powers of the various
LFMs, before output losses.
900 MHz PA
The RF signals from the outputs of the RF Splitter are applied directly into the
Linear Final Module (LFM) for final amplification. Each LFM contains a
branchline coupler that splits the LFM’s input signal and feeds the dual Class AB
push-pull amplifiers that amplify the RF signals. The amplified signals are then
combined on the LFM and sent directly to the RF Combiner circuit for final
distribution. See Table 2 for the approximate total summed output power of the
900 MHz LFMs, before output losses.
1500 MHz PA
The two RF signals from the outputs of the RF Splitter are input directly into the
Linear Final Module (LFM) for final amplification. Each LFM contains a
branchline coupler that splits the LFM’s input signal and feeds the dual Class AB
push-pull amplifiers that amplify the RF signals. The amplified signals are then
combined on the LFM , via a branchline coupler, and sent directly to the RF
Combiner circuit for final distribution. See Table 2 for the approximate total
summed output power of the 1500 MHz LFMs, before output losses.
The current drains of the 1500 MHz LFMs are monitored by the A/D converter on
the DC/Metering board. A voltage signal representative of the LFM current drain
is sent to the BRC. A Power Amplifier alarm is generated if the signal is outside of
either the upper or lower limits.
RF Interconnect Board (40W- 800 MHz PA Only)
The RF Interconnect Board consists of transmission line paths which route the
three output signals from the LFMs to the three inputs of the RF Combiner/
Peripheral Module.
Combiner Board (40W- 800 MHz, 70W- 800 MHz, 800 MHz QUAD and
900 MHz QUAD PAs)
The Combiner Board combines pairs of signals into single signals, thereby
combining the six signals from the LDMs into three signals. The resulting three
signals are applied to the RF Combiner/Peripheral Module.
RF Combiner/Peripheral Module (40- 800 MHz, 70W- 800 MHz PAs)
This module consists of two portions: an RF combiner and a peripheral module.
The RF Combiner portion of the module combines the three RF signals from the
RF Interconnect Board (40W- 800 MHz PA) or the Combiner Board (70W- 800
MHz PA) into a single signal using a Wilkinson coupler arrangement.