Resistive Power Splitter offer a wider bandwidth than transformer types, as the resistors are more frequency independant. The drawback is the power loss in the series resistors (we use a star type here) and the poor isolation. We used two tools to design this board :

• Resistive Power Split Calculator

• Coplanar Waveguide Impedance Calculator

The board is made of FR4 by JLCPCB. The case is made of Aluminium by D-PHYS workshop 👍

The Simulations were done with the venerable RFSim99. It was mainly used to verify, that the change of te resistor values by a small amount would not be a suicide action. But the "circuit" behaved decently - and we tried to get away with that.

Even so we used 24 Ω resistors instead of the calculated values (25 Ω, 9.54 dB and a perfect match) the insertion loss did merely change. The matching was better than 10 dB for all frequencies measured up to 3 GHz. The plots below show the details. Ports are numbered from the left in ccw orientation.




It can be seen, the the insertion loss is independant of the location of the port. The measurements show almost identical values for adjacent as well as for opposite locii.

The cover of the case showed no influence. It was mounted anyway. For mechanical protection.

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