Wilkinson Power Divider
Understanding Wilkinson Power Dividers
The Wilkinson divider is arguably the single most important building block in RF power distribution. Its unique combination of matched ports, isolation, and theoretically lossless equal-phase splitting makes it ideal for feed networks, test setups, and combining amplifiers.
Wilkinson Design
- Branch impedance: Z0 x sqrt(2) = 70.7 ohms (for 50-ohm system).
- Branch length: Quarter-wave (lambda/4) at center frequency.
- Bridge resistor: 2 x Z0 = 100 ohms between output ports.
Wilkinson Properties
- Insertion loss: 3 dB (ideal). Power splits equally.
- Port match: All three ports matched to Z0.
- Isolation: Infinite between outputs (ideal). 20-30 dB practical.
- Phase: Equal phase at both outputs.
Multi-Stage Wilkinson
The basic single-section Wilkinson has ~20% bandwidth. Multi-section Wilkinsons (2-3 quarter-wave sections with different impedances and resistors) extend bandwidth to octave or wider.
Frequently Asked Questions
What is a Wilkinson power divider?
A Wilkinson divider splits a signal into two equal outputs with high isolation between them. It uses quarter-wave lines and a bridge resistor. It is the most widely used power divider because it is matched at all ports and provides output isolation.
What makes the Wilkinson unique?
The Wilkinson is the only three-port network that is simultaneously matched, lossless (for the equal split), and provides isolation between output ports. A simple tee junction cannot achieve all three properties simultaneously.
What is the bandwidth of a Wilkinson?
A single-section Wilkinson has about 20-30% bandwidth. Multi-section Wilkinsons extend bandwidth to 50-100% or more. The bandwidth is limited by the quarter-wave transformer response. N-way Wilkinsons use multiple stages for broader bandwidth.