Comtech-ef-data PCB-4000 Manual do Utilizador descarregar pdf (Página 18)

PCB-4000 1+1 Phase Combiner Revision 2

Introduction MN/PCB4000.IOM

1–4

• TheRFsignalsfromthePCCBarefedtotheRFinputoftherespectiveSSPAviaasetof

phase‐matched cables. Again, the phase length (and matching) of these cables is

essentialtosystemoperationandnosubstitutesshouldbeused.Theroutingshouldnot

besuchtoca

useextremebends.



• Theoutput waveguide combining system consists of balanced waveguide lengths, two

waveguide transfer switches, a “Magic‐Tee”  combiner  with termination, and couplers

fortestandalignment.

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 the Figure 1‐2  system block diagrams,

when two si gnals  of equal phase and amplitude are fed into the “Magic‐Tee” combiner, the

individual power of each SSPA is summed at the ou

tput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 practi

ce,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eff

ects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

Naturally,twoseparateamplifiersarelikelytohavedifferentphaseandgaincharacteristics.The

PCB‐4000 1+1 system is designed such that the phase difference between the two amplifier

pathsiscompensatedbyadjustingthephaseshifterinthePhaseCombinerControlBox.Thisis

done at the factory for the full ampli

fier bandwid th, and should not normally require further 

adjustmentinthefieldunlessanamplifierhasbeenreplaced.(Seealignmentpr ocedure).

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