RF Power Splitter Design: A Wilkinson Circuit Approach

A Wilkinson power splitter is a common type of passive RF (Radio Frequency) component used to divide power among multiple ports in a circuit.

The design of a Wilkinson power splitter is based on the Wilkinson divider topology. It provides equal power division between output ports while maintaining good impedance matching. This design can also function as a 2-way RF power combiner. Wilkinson power splitters are widely used in RF and microwave systems, finding applications in communication systems, test and measurement equipment, and radar systems. They’re especially useful where equal power distribution is critical and minimal signal reflections are desired.

Let’s explore the design of a 2-way Wilkinson RF power splitter at 800MHz, using a dielectric substrate with an εr of 4.6. This design can be extended for N-Way power dividers or splitters, such as 8-WAY and 16-WAY configurations.

As shown above, the basic Wilkinson power splitter consists of a three-port network with a resistor at each port and two transmission lines.

The Wilkinson power divider is a robust design among all. It ensures that all output ports are matched. Any reflected power is dissipated internally. Compared to a T-junction power divider, it offers better isolation between output ports. The figure shows both the geometry layout and the transmission line equivalent circuit of the power splitter.

The figure above depicts a Wilkinson 2-way power splitter circuit used for simulation using Microwave Office software. Simulate the RF circuit from 500 to 1100 MHz and check the results. Set the microstrip substrate parameters as shown in the table below in the simulation circuit.

Simulation Results

Result 1: Return Loss at Ports

Result 2: Splitter Power Loss Chart

The figures show the results of our design. S11, S22, and S33 (return loss at each port) are better than -15dB. S21 and S31 (insertion loss) are around -3dB.

RF Power Divider Layout

The figure depicts the final layout of the 2-way RF power splitter based on the Wilkinson design concepts. After generating the basic layout, it is modified to meet PCB requirements and accommodate RF connectors. Chip resistors of 50 Ohm and 100 Ohm values are manually placed.

Consider reviewing microstrip line basics and types to gain a better understanding of RF circuit design concepts, as demonstrated in this example.

Conclusion

In summary, during the 2-way Wilkinson power splitter design, engineers often use RF simulation tools (like Microwave Office or ADS) and adhere to best practices to optimize the circuit’s performance. Proper impedance matching, attention to component values, and adherence to the design principles contribute to the success of Wilkinson power splitters in various RF applications.