design power combining with wilkinson power divider,whether the isolator between the two outputs of wilinson is necessary? if so ,but why?is there some document about these,thanks!
Each arm of the Wilkinson splitter/combiner has the impedance Z = Zo*1.41, where Zo is the impedance of the ports (e.g. for Zo=50 ohms result Z = 70.7 ohms).
The isolator connected to the output ports guaranties a perfect 50 ohms, and in this way keeping the designed performances of the splitter/combiner (insertion loss and isolation).
The isolation tells you how much power is going into the the other port(If it is used as combining).
You usually not interested in having power going into the output of a power amplifier, it can mean the destruction of the device if the power is large enough.