User's Manual

68P80801E35-A 9/1/2001 9
EBTS System Manual - Vol 2 Power Amplifier (PA)
PA Theory of Operation
DC/Metering Board (Non-QUAD PA)
The DC/Metering Board provides the interface between the PA and the Base
Radio backplane. The preamplified/modulated RF signal is input directly from
the Exciter via the Base Radio backplane.
The RF input signal is applied to the input of the Linear Driver Module (LDM).
The RF feedback signal is fed back to the Exciter, where it is monitored for errors.
The primary function of the DC/Metering Boards is to monitor proper operation
of the PA. This information is forwarded to the Base Radio Controller (BRC) via
the SPI bus. The alarms diagnostic points monitored by the BRC on the PA
include the following:
❐ Forward power
❐ Reflected power
❐ PA temperature sense
❐ Fan Sensor
RF Combiner/Peripheral
Module
• Contains a combiner circuit that combines the three RF signals from
the RF Interconnect Board (40W- 800 MHz PA) or the Combiner
Board (70W-800 MHz PA). It then routes the combined RF signal
through a single stage circulator and a Low Pass Filter. The final
output signal is routed to the blindmate RF connector (40W-800 MHz
and 70W-800 MHz PAs).
• Contains a combiner circuit that combines the three RF signals from
the Combiner Board. It then routes the combined RF signal through a
dual stage circulator and a Low Pass Filter. The final output signal is
routed to the blindmate RF output connector. (800 MHz QUAD and
900 MHz QUAD PAs)
• Contains a Quadrature combiner circuit to combine the RF signal
from the two LFMs. It routes the combined RF signal through a
circulator and a Low Pass Filter. The output signal is routed to the
blindmate RF connector (900 MHz and 1500 MHz PAs)
• Contains an RF coupler that provides an RF feedback signal to the
Exciter via a blindmate RF connector on the DC/Metering Board.
Also contains a forward and reverse power detector for alarm and
power monitoring purposes.
• Contains the thermistor that senses PA temperature and feeds the
signal back to the DC/Metering Board for processing (40W-800
MHz, 70W-800 MHz, 900 MHz and 1500 MHz)
Fan Assembly • Consists of three fans used to keep the PA within predetermined
operating temperatures
NOTE: * The power outputs described in this section for the 800 QUAD and 900 QUAD PAs are references to the
single carrier mode operating at 52W average power out from the PA output connector.
Table 2 Power Amplifier Circuitry (Continued)
Circuit Description