RF Passives › Power Dividers
Designing Wilkinson Power Dividers
Step-by-step design for equal-split, unequal-split and wideband Wilkinson dividers. Enter your substrate and the tool computes exact PCB trace widths and lengths — no manual calculation needed.
Introduction
What is a Wilkinson Power Divider?
A Wilkinson divider splits one RF signal into two outputs while keeping all three ports matched to Z₀ and the outputs isolated from each other — something a simple T-junction cannot do.
✦ All ports matched to Z₀ — no reflections ✦ Output-to-output isolation — Port 2 and Port 3 cannot see each other ✦ Lossless when balanced — the resistor dissipates zero power during normal operation
Used in: antenna feed networks, PA combiners, phased arrays, test equipment signal splitters.
✦ All ports matched to Z₀ — no reflections ✦ Output-to-output isolation — Port 2 and Port 3 cannot see each other ✦ Lossless when balanced — the resistor dissipates zero power during normal operation
Used in: antenna feed networks, PA combiners, phased arrays, test equipment signal splitters.
Beginner tip: Put 10 mW in — each output gets 5 mW (−3 dB). The two quarter-wave arms and one resistor give perfect matching and isolation simultaneously, which a simple wire T-junction cannot do.
PCB Substrate — enter your board parameters to get exact trace widths & lengths
Substrate presets: FR4 (εr=4.4, h=1.6mm, tan δ=0.020) · Rogers 4350B (εr=3.66, h=0.762mm, tan δ=0.0037) · Rogers 5880 (εr=2.2, h=0.787mm, tan δ=0.0009) · RO4003C (εr=3.55, h=0.813mm, tan δ=0.0027)
The Hammerstad-Jensen closed-form model is used — same as our Microstrip Calculator. Accuracy within 1–2% of full-wave EM simulation.
The Hammerstad-Jensen closed-form model is used — same as our Microstrip Calculator. Accuracy within 1–2% of full-wave EM simulation.
Select divider type to design
Equal-Split Wilkinson — Circuit Schematic
Port 1 = Input | Port 2 & Port 3 = Outputs (equal −3 dB each)
Step 01 — Electrical Design
Frequency, Impedance and Component Values
Electrical Inputs
MHz
Ω
Electrical Results
70.71 Ω
100 Ω
31.25 mm
Z₁ = Z₀ × √2 — Each arm acts as a quarter-wave impedance transformer converting the 25 Ω junction (two 50 Ω in parallel) back to 50 Ω at the input.
R = 2 × Z₀ — The isolation resistor absorbs any imbalance between the two outputs and creates port-to-port isolation.
R = 2 × Z₀ — The isolation resistor absorbs any imbalance between the two outputs and creates port-to-port isolation.
PCB Trace Dimensions — on your substrate
| Trace / Element | Width | Length (λ/4) | Notes |
|---|---|---|---|
| 50 Ω port traces | — | — | Feed lines to all 3 ports |
| 70.7 Ω arms (×2) | — | — | Both arms identical |
| Isolation resistor R | — | 0402 chip, between Port 2 & 3 junction | |
Enter substrate parameters above to see PCB dimensions.
Step 02 — PCB Layout
Five Layout Rules
① Both arms must be identical in length and shape. Any asymmetry degrades isolation and output balance.
② Place the isolation resistor directly at the output junction. No extra routing between the resistor pads and the trace — use 0402 or 0201.
③ Keep copper pour ≥ 3× trace width away from the arms. Ground fill changes the effective εr and shifts the resonant frequency.
④ Solid continuous ground plane below. No splits or gaps under the divider.
⑤ Add via stitching alongside the arms on multi-layer boards.
② Place the isolation resistor directly at the output junction. No extra routing between the resistor pads and the trace — use 0402 or 0201.
③ Keep copper pour ≥ 3× trace width away from the arms. Ground fill changes the effective εr and shifts the resonant frequency.
④ Solid continuous ground plane below. No splits or gaps under the divider.
⑤ Add via stitching alongside the arms on multi-layer boards.
Most common mistake: Asymmetric routing of the output traces after the junction. Keep symmetry all the way to the loads or connectors.
Design Complete
Equal-Split Wilkinson Summary
Unequal-Split Wilkinson — Circuit Schematic
Port 2 = more power (K²× Port 3). Both outputs remain matched to Z₀.
Step 01 — Electrical Design
Specifications, Arm Impedances and Resistor
Electrical Inputs
MHz
Ω
×
Electrical Results (Pozar formulas)
— Ω
— Ω
— Ω
— dB
— dB
PCB Trace Dimensions — on your substrate
| Trace / Element | Width | Length (λ/4) | Notes |
|---|---|---|---|
| 50 Ω port traces | — | — | Feed lines |
| Z_A arm (to Port 2) | — | — | More power arm |
| Z_B arm (to Port 3) | — | — | Less power arm — width & length differ from Z_A |
| Isolation resistor R | — | 0402 chip, nearest E24 | |
Enter substrate parameters above to see PCB dimensions.
Design Complete
Unequal-Split Wilkinson Summary
Wideband Two-Section Wilkinson — Circuit Schematic
Two λ/4 sections per arm with two isolation resistors — ≈doubles bandwidth vs single-section
Step 01 — Electrical Design
Band Edges, Section Impedances and Resistors
Electrical Inputs
MHz
MHz
Ω
Electrical Results
—
—
—
—
—
—
Z_s1, Z_s2 use the standard 2-section binomial (geometric-progression) impedance step from Z₀ to 2Z₀ — the same textbook approach used for any 2-section quarter-wave matching transformer.
R₁, R₂ are a practical approximation for isolation at f₀, not a full-band Chebyshev optimisation. They'll give good, buildable starting values; for a production design push the final component values through an EM simulator across your full band.
R₁, R₂ are a practical approximation for isolation at f₀, not a full-band Chebyshev optimisation. They'll give good, buildable starting values; for a production design push the final component values through an EM simulator across your full band.
PCB Trace Dimensions — on your substrate
| Section / Element | Width | Length (λ/4) | Notes |
|---|---|---|---|
| 50 Ω port traces | — | — | Feed lines |
| Z_s1 sections (×2 arms) | — | — | Input section, 4 traces total |
| Z_s2 sections (×2 arms) | — | — | Output section, 4 traces total |
| R₁ inner resistors (×2) | — | 0402, at mid-section junction | |
| R₂ outer resistors (×2) | — | 0402, at output junction | |
Enter substrate parameters above to see PCB dimensions.
Design Complete
Wideband Wilkinson Summary