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1.3.2
System Gain
The gains of the amplifiers are calibrated at the factory to provide optimum system performance.
The amplifier gain difference is automatically compensated for by the PCCB M&C System. Upon
power up, the M&C reads the gain of each individual amplifier as calibrated at the factory, and
automatically attenuates the amplifier with the most gain so as to be equal with the lower gain
unit.
For example, if SSPA #1 had a factory-calibrated gain setting of 76 dB, and SSPA #2 had a
factory-calibrated gain setting of 73 dB, the M&C system would automatically set the attenuation
setting of SSPA#1 to 3 dB to equalize the system gain. Although not generally needed or
recommended, a user input gain offset setting is also provided for system fine-tuning.
See Chapter 3. OPERATION and ADJUSTMENT PROCEDURES for
operational and alignment information.
Due to the power divider and cable losses, the overall gain of the system will be less than the
individual gain of each amplifier. Please refer to the system test data sheet for actual system
gain.
1.3.3
System Attenuation
The PCB-4000A makes it easy to adjust the overall system gain. Upon input of the requested
attenuation setting, the PCB-4000A automatically adjusts the gain of each SSPA accordingly,
resulting in the desired attenuation value while maintaining optimum power combining conditions.
The SSPAs included in the system are calibrated over a range 10 dB beyond specification (30 dB
vs. 20 dB). As explained above, a portion of the 30 dB range is required for gain equalization.
Therefore, the maximum allowable attenuation in a 1+1 system is software limited to 24 dB, but
still exceeds system specifications.
1.3.4
Soft Fail Protection
In the event of a failure of one of the SSPAs, the PCB-4000A controls the waveguide switches
such that the good unit's power is routed around the "Magic-Tee" combiner directly to the output
port. This results in only a 3 dB power loss, or "soft failure". Without the waveguide switches, a
failure in one unit would result in a 6 dB power loss.
Introduction
PCB-4000A 1+1 Phase Combiner
1–5
Revision 2
MN-PCB-4000A
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