Design of Wilkinson RF Power Divider, splitter, combiner, Hybrid
For any beginner in RF circuit design, 2way hybrid design is the first step to get familiar with the concepts of rf circuit design right from simulation, tuning, optimization and layout using RF design softwares. The most popular softwares are microwave office and ADS. In this page we will go through wilkinson 2-way RF splitter design at 800MHz using dielectric substrate having εr of 4.6. The same design can be extended for N-Way power divider or splitter such as 8-WAY and 16-WAY. This higher number of ports rf combiner and splitter is widely used in VSAT Hub stations or central stations for multiple signal combining and splitting process.
Wilkinson power divider is the robust among all designs. It will have all the output ports matched. It will have only reflected power which will be dissipated. It provides better isolation between output ports in comparison to T-junction power divider. Figure above mentions both geometry layout as well as transmission line equivalent circuit of the power splitter.
RF Simulation Circuit
The figure depicts wilkinson 2way power splitter circuit used for simulation using Microwave Office software. Simulate the rf circuit from frequency 500 to 1100 MHz and check the results as shown. Set the microstrip substrate parameters as shown in the table below in the simulation circuit.
|Relative Dielectric Constant(εr)||4.6|
|Substrate thickness(H)||1.6 mm|
|Conductor thickness(T)||0.05 mm|
|Rho(Metal Bulk resistivity normalized to gold)||1|
|Tand(Loss tangent of dielectric)||0.025|
The figure depicts results of our design. As mentioned S11, S22, S33 are better than -15dB. S21 and S31 are better than about -3dB.
The figure depicts final layout of 2way rf power splitter as per wilkinson design concepts mentioned. After the basic layout is generated, the same is modified as per PCB requirement and placement of RF connectors. The mounting of chip resistors of value 50 Ohm and 100 Ohm is also made manually. Refer microstrip line basics and types which will help rf designer to understand concepts before RF circuit design as mentioned in this example.
The design steps mentioned in this article can be applied to design of any rf circuit/subsystems using rf design softwares. This include design of rf directional coupler, rf circulator, rf isolator, mixer, rf frequency converter, rf filter, power amplifier, LNA etc.