How does a Wilkinson power divider work?

From RF Design Wiki · By the RF Design Wiki editorial team · Published October 21, 2026 · Last reviewed October 21, 2026 · How we research

The Wilkinson power divider, described by Ernest Wilkinson in 1960, splits an input equally between two in-phase outputs while matching all ports and isolating the outputs from each other. The equal-split version uses two quarter-wave lines of impedance √2·Z₀ (70.7 Ω in a 50 Ω system) and a resistor of 2Z₀ (100 Ω) between the outputs.^[1]^[2]

Why is the resistor needed?

When the outputs are driven in phase (even mode), no current flows in the resistor and the lines transform each 50 Ω load to 100 Ω, which in parallel give 50 Ω. When one output reflects (odd mode), the resistor absorbs the signal, isolating the other output. A T-junction without the resistor is lossless but cannot match all ports.^[2]

What bandwidth does it have?

A single-section divider gives roughly 20 dB isolation and return loss over about ±20% bandwidth around f₀, depending on criterion. Multisection designs extend this to octaves or more.^[2]

Can it split unequally?

Yes, with different line impedances and resistor value; Pozar gives design equations for a power ratio K² = P₃/P₂. N-way versions exist but are awkward to lay out beyond two ways in planar form.^[2]^[1]

What are other power dividers?

Resistive dividers: broadband to DC, 6 dB loss per path, no isolation.
Reactive T-junctions: lossless, unmatched outputs.
Hybrids: 90° or 180° outputs.

Frequently asked questions

What is the insertion loss of an ideal Wilkinson?

3.01 dB to each output (the power split), plus real line and resistor losses.

Does it combine signals too?

Yes; in-phase equal signals combine losslessly, while differences are dissipated in the resistor.

Why 70.7 Ω lines?

They transform 50 Ω to 100 Ω at each arm so two arms in parallel make 50 Ω.

References

Online sources accessed October 21, 2026; printed works cited by edition. See all sources.

“An N-Way Hybrid Power Divider”. E. J. Wilkinson, IRE Transactions on Microwave Theory and Techniques, vol. 8, no. 1, pp. 116-118. January 1960.
“Microwave Engineering, 4th ed.”. D. M. Pozar, Wiley. 2012.

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