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1.3
Theory of Operation
As mentioned previously, phase combining is a common technique to increase the available
output power of an amplifier system. Referring back to Figure 1-2, when two signals of equal
phase and amplitude are fed into the "Magic-Tee" combiner, the individual power of each SSPA is
summed at the output port and cancelled in the termination port.
In real systems, the phase and amplitude of the two signals are never exactly equal, so there is a
small amount of power that is absorbed by the load termination. This terminated port is
sometimes referred to as the "wasted" power port. In practice, however, it is possible to keep
phase and amplitude imbalances at low enough levels such that overall combining losses are
only in the 0.2 to 0.5 dB range.
Figure 1-3 shows the effects of phase imbalance on the power combining efficiency.
Figure 1-3. Combining Loss vs. Phase Imbalance Summary of Specifications
1.3.1
Phase and Gain Equalization
Phase and gain equalization are performed at the factory, and no user
intervention is required unless an amplifier or other critical system component,
such as the phase combiner box, needs to be replaced.
The following paragraphs are provided for informational purposes only.
See Chapter 3. OPERATION and ADJUSTMENT PROCEDURES for
operational and alignment information.
Naturally, two separate amplifiers are likely to have different phase and gain characteristics. The
PCB-4000A 1+1 system is designed such that the phase difference between the two amplifier
paths is compensated by adjusting the phase shifter in the PCCB. This is done at the factory for
the full amplifier bandwidth, and should not normally require further adjustment in the field unless
an amplifier has been replaced.
Introduction
PCB-4000A 1+1 Phase Combiner
1–4
Revision 2
MN-PCB-4000A
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