User's Manual

68P80801E35-B 5/1/2002 9
EBTS System Manual - Vol 2 Power Amplifier (PA)
PA Theory of Operation
PA Theory of Operation
Table 2 describes the basic functions of the PA circuitry. Figures 6 and 7 show the
functional block diagrams of 40W, 800 MHz and 70W, 800 MHz PA, respectively.
Figure 8 shows the functional block diagram of the 60W, 900 MHz PA. Figure 9
shows a functional block diagram of the 40W, 1500 MHz PA. Figure 10 shows a
functional block diagram of 800 MHz. Figure 10 shows a functional block
diagram of 900 MHz QUAD PA.
Table 2 Power Amplifier Circuitry
Circuit Description
DC/Metering Board • Serves as the main interface between the PA and the backplane board
• Accepts RF input from the Exciter via a blindmate RF connector
• Routes the RF input via a 50 Ω stripline to the Linear Driver Module
RF amplifier
• Routes the RF feedback from the RF Combiner/Peripheral Module
to the Exciter via a blindmate RF connector
• Provides digital alarm and metering information of the PA to the
BRC via the SPI bus
• Routes DC power to the fans and PA
• Contains the thermistor that senses the PA temperature (800 MHz
QUAD and 900 MHz QUAD)
• Contains a Linear Driver Module and Linear Final Module Bias
Enable Circuit (900 MHz QUAD)
• Contains a Voltage Variable Attenuator Circuit (900 MHz QUAD)
Linear Driver Module
(LDM)
• Contains two Class AB stages with the final stage in a parallel
configuration (70W-800 MHz, 40W-800 MHz, 800 MHz QUAD)
• Contains three cascaded Class AB stages with the first two stages
configured as distributed amplifiers and the final stage in parallel
configuration (900 MHz QUAD)
• Contains three cascaded stages (Class A + Class AB + Class AB) with
the final stage in push-pull configuration (900 MHz)
• Contains four cascaded stages (Class A + Class AB + Class AB +
Class AB) with the final stage in a push-pull configuration (1500
MHz)
• Amplifies the low-level RF signal ~25 mW average power from the
Exciter via the DC/Metering Board (900 MHz)
• Amplifies the low level RF signal ~11mW average power from the
Exciter via the DC/Metering Board (70W-800 MHz, 800 MHz
QUAD*, 900 MHz QUAD*)
• Amplifies the low-level RF signal ~8 mW average power from the
Exciter via the DC/Metering Board (40W- 800 MHz, 1500MHz)
• Provides an output of:
~8 W (70W, 800MHz) average power
~4 W (40W, 800 MHz) average power
~6 W (800 MHz QUAD* and 900 MHz QUAD*) average power
~17 W (900MHz) average power
~16 W (1500MHz) average power