RF & microwave systems may require power to be divided between two or more applications. In these cases, a device to facilitate the division of an input power is needed.
The earliest power dividers, which were T-junctions, had no isolation between output ports. In the figure above, which depicts a T-junction, power is input through P1 and supposed to be divided evenly between P2 and P3 without reflection. However, due to the poor isolation, power directed toward P2 could be reflected to P3 if the ports are not matched, making the power output through P2 and P3 uneven and providing the possibility of damaging a part of the system.
Wilkinson power dividers were invented circa 1960 by engineer Ernest J. Wilkinson. They divide power from an input port to two or more output ports. Unless otherwise noted, the power is divided equally and with zero phase shift between the outputs. As an example, the figure below displays a 2 way power divider with three ports. Power enters through Port 1 and is divided between Port 2 and Port 3. Each of the outputs (ports 2 and 3) have half the energy of the input (port 1).
Isolation is the most important parameter for a power divider. If there is an impedance mismatch or other issue at an output port, high isolation prevents the other port(s) from being affected. A high isolation is also effective in limiting power leakage from one output port to another. In the figure above, there is a resistor with impedance 2Z0 between ports 2 and 3 to ensure that they are isolated. If Port 2 was damaged or could not otherwise function properly, it would not affect the power that is directed through Port 3.
Power dividers are passive RF components, so they can also combine power. Using the figure above, power can be input through Port 2 and Port 3 to be combined at Port 1. In this case, Ports 2 and 3 would be the inputs and Port 1 the output.
Power dividers are often employed in multi-channel radio frequency systems and other telecommunications and defense systems that may require combining or dividing power.
When browsing for power dividers, make sure to check that they are compliant with US specifications and international standards. In particular, attention should be given to frequency range, VSWR, Insertion Loss, and especially isolation as mentioned earlier.