User's Manual

16 68P80801H45-1 1/20/2002
Power Amplifier (PA) EBTS System Manual - Vol 2
PA Theory of Operation
The Peripheral module provides a power monitor circuit that monitors the
forward and reflected power of the output signal. This circuit furnishes the A/D
converter on the DC/Metering Board with input signals, representative of the
forward and reflected power levels.
For forward power, a signal representative of the measured value is sent to the
BRC via the SPI bus. The BRC determines if this level is within tolerance of the
programmed forward power level. If the level is not within tolerance, the BRC
will issue a warning to the site controller, which, in turn, will shut down the
Exciter, if required.
Reflected power is monitored in the same manner. The BRC uses the reflected
power to calculate the voltage standing wave ratio (VSWR). If the VSWR is
calculated as excessive, forward power is rolled back. If the VSWR calculation is
exceedingly out of tolerance, the BRC issues a shut-down command to the Exciter.
NOTE
The Thermistor that monitors the operating
temperature of the 800 MHZ QUAD and 900 MHz
QUAD PAs is located on the DC/Metering Board
Fan Module
The PA contains a fan assembly to maintain normal operating temperature
through the use of a cool air intake. The fan assembly consists of three individual
fans in which airflow is directed across the PA heatsink.
The current draw of the fans is monitored by the DC/Metering Board. A voltage
representative of the current draw is monitored by the BRC. The BRC flags the
iSC if an alarm is triggered. The PA LED on the front panel of the BRC also lights,
however the PA does not shut down due to a fan failure alone.