Powerwave Technologies G3L-929-135, Инструкция по установке и обслуживанию

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4-2 044-05xxx Rev A
Figure 4-1. Functional Block Diagram
4-4.1 Preamplifier
The RF carriers are applied to the input port of the MCPA, where they are fed to the preamplifier
stage. The preamplifier provides two stages of class-A mode-amplification. The output of the
preamplifier is then split into two paths, one to the main amplifier and one to the error amplifier.
4-4.2 Main and Error Amplifiers
The main amplifier provides a balance of gain and power and employs class AB amplification for
maximum efficiency. The error amplifier and feed forward loops correct signal distortion
introduced by non-linearity in the class AB main amplifier. The error amplifier operates in class A
mode. The RF signal from the preamp is coupled to an attenuator and phase shifter in the first
feed-forward loop where it is phase shifted by 180 degrees and amplified in the pre-main
amplifier. The output from the pre-main amplifier is fed to the class AB main amplifier. The signal
output from the main amplifier is sampled using a coupler, and the sample signal is combined
with the main input signal and input to the second feed-forward loop.
The error signal is attenuated, phase shifted 180 degrees, then fed to the error amplifier where it
is amplified to a level identical to the sample output from the main amplifier. The output from the
error amplifier is then coupled back and added to the output from the main amplifier. The control
loops continuously make adjustments to cancel out any distortion in the final output signals.
4-4.3 Alarm Monitoring and Control
The alarm logic controls the +5 Vdc bias voltage that shuts down the amplifier. During routine
operation, all normal variations are automatically compensated for by the feed-forward loop
control. However, when large variations occur beyond the adjustment range of the loop control, a
loop fault occurs. When this happens, an alarm indicator is illuminated on the front panel of the
sub-rack. The fault is transmitted back to an external summary module via the external alarm
interface connection on the front panel of the sub-rack.