4-16
888-2523-001
7/26/05
WARNING: Disconnect primary power prior to servicing.
Section 4 Theory of Operation
ATLAS Analogue
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Precision RF power measurement #3 System Forward Power
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Precision RF power measurement #4 System Reflected Power
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Precision RF power measurement #5 Drive Chain A Power
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Precision RF power measurement #6 Drive Chain B Power
4.4.3.2
Reject Load RF Detector (Relative)
The reject load RF detectors are a diode based envelope detector. These detectors are
intended to provide relative readings only, not accurate absolute power measurements.
The inputs for these detectors come from the 40dB attenuators being used as reject
loads for the PA module combiner. Each detector has 2 dynamically adjustable gain
settings, Low and High. The chosen sample levels from the reject loads and the gain of
the detectors allow them to operate in the Low gain position for normal operation.
In other words, for a 1000W reject load (which is actually a 40dB attenuator) with
1000W applied, the RF input sample to the detector would be 100mW. In the Low gain
position, this would give approximately 3Vdc detected output (the actual output voltage
is dependent on frequency). This 3Vdc level (adjusted for frequency) is used to protect
the reject loads from over-dissipation.
The High gain setting is only used when adjusting module or cabinet phasing to
minimize combiner reject load power. When you leave the "Phase Align" screen on the
GUI all detectors default back to the Low gain setting.
The reject load RF detector samples are used for 2 purposes:
•
Overload protection of the reject loads
•
PA Module and Cabinet RF phase alignment
4.4.3.2.1 Reject Load Protection
The reject load detector outputs are sent to comparators for detection of overloads
which could potentially damage the load. If these loads were dissipating their maximum
power levels then their sample outputs to the detectors would be 40dB less or 100mW.
The detectors are calibrated (by a fixed voltage divider on the RF Controller board) to
produce a 3Vdc output at this maximum RF input level.
If the detector output reaches 3Vdc the fault comparators will trip, causing a
FAULT_OFF to be sent over the parallel control bus, shutting the transmitter off. The
micro module will communicate the cause of the fault to the Main Controller over the
CAN bus.
Summary of Contents for ATLAS ANALOGUE
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