4 feeds is use to obtain good axial ratio, phase center stability, rad. pattern in hemisphere, because it is GNSS antenna (f1~1230 MHz, f2=1560 MHz). Below the power and efficiency vs frequency is presented.
1 port is excited:
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4 ports are excited:
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«power outgoing all ports» contains reflected and transmited to other port power.
An efficiency calculation takes «power outgoing all ports» into account
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Calculation was performed by combining 3d farfield, but when real devider was used in model, the efficiency results have been the same.