Click here to go to our general discussion of Wilkinson power power dividers
Click here to go to our unequal-split power divider calculator, it handles Wilkinsons, rat-races and branchline couplers!
Our material on unequal-split Wilkinsons is spread onto the following pages:
Unequal-split Wilkinsons simplified (new for July 2023!)
Split Tee Power Divider - the original unequal Wilkinson splitter from 1965
Unequal split Wilkinsons, the rest of the story (Microwaves101 exclusive, from 2009!)
Maximally-flat transformers used in unequal split Wilkinsons
Kouzoujian's N-way splitter - uses unequal splitters in a planar layout (Microwaves101 exclusive!)
Traveling wave combiner (mostly used to create equal outputs but unequal math is required)
N-way, unequal split Wilkinsons - by Paul Hubbard and Greg Ordy of Seed Solutions (Microwaves101 exclusive!)
Our page on the rest of the story on unequal-split Wilkinsons derives the math behind the impedance calculations. We'll show you an extra degree of freedom that the classic unequal-split Wilkinson equations don't provide.
We are talking about two-way Wilkinson splitters here, but of course you can make unequal split N-way dividers. The way to make power split unequally requires two things: the quarterwave sections must be of different impedance, to encourage more of the signal to travel in/out the lower-impedance arm, and a second set of quarter-wave sections are needed, to transform the arm impedances back to 50 ohms. The structure looks similar to a two-stage Wilkinson without the second isolation resistor (here "RW" is the Wilkinson isolation resistor). The math for computing the line impedances in the figure below is provided on this page.
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Topology for unequal-split Wilkinson
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The above image and many more are available in a Word document you can get in our download area (for free).
What constitutes a valid solution to the unequal splitter network? There are really just three criteria that must be met:
- All ports are perfectly matched at center frequency
- Infinite isolation is achieve at center frequency
- In the even mode (exciting Port 1) the splitter is lossless.
When you look at any of the unequal-Wilkinson solutions, keep an eye on these three properties!
What about N-way unequal splits? We offer two ways to do that. The direct way is located here. You can probably figure out a way to make unequal splits of any N-value (3,4,5,6,7...) by cascading two-way and three-way Wilkinsons; this is often done in antenna feed networks for tapered apertures. Maybe we will cover that later...