Power Divider
Understanding Power Dividers
Power dividers are among the simplest and most widely used passive components in RF systems. Every phased array antenna requires a power divider network (or corporate feed) to distribute transmit power and combine received signals from the array elements.
Wilkinson Power Divider
The Wilkinson divider uses quarter-wave impedance transformers and a resistor between output ports to achieve three critical properties simultaneously: impedance match at all ports, equal power division, and isolation between output ports. The isolation resistor absorbs reflected power from mismatched loads.
Design Variations
- Equal split (3 dB): Two outputs at -3 dB each (minus insertion loss).
- Unequal split: Specified power ratio between outputs (e.g., 6 dB and 1.25 dB).
- N-way: Radial or corporate-feed dividers splitting power to N outputs.
- Wideband: Multi-section Wilkinson designs covering 10:1 bandwidth.
Insertion loss: -3 dB per output (power halved)
Isolation: infinite between outputs (ideal)
Match: perfect at all ports
Wilkinson quarter-wave impedance:
Z_arm = Z0 x sqrt(2) = 70.7 ohms (for 50-ohm system)
Isolation resistor: R = 2 x Z0 = 100 ohms
N-way divider loss:
Theoretical: -10 log10(N) dB per output
Frequently Asked Questions
What is a power divider?
A power divider splits an input signal into two or more outputs of equal or specified power levels. The Wilkinson design provides matched ports and isolation between outputs, making it the standard for antenna feeds, LO distribution, and signal splitting.
What is the difference between a power divider and a coupler?
A power divider splits power equally (or at a specified ratio) between all outputs. A directional coupler samples a small fraction of power from the main line while passing most power through. Power dividers have symmetric ports; couplers have a main line and coupled port.
How much loss does a power divider have?
The inherent splitting loss is -3 dB for a 2-way divider, -6 dB for a 4-way, and -10 dB for a 10-way. Additional loss from conductor and dielectric losses adds 0.2-1 dB depending on frequency and construction. The splitting loss is not dissipated; the power is delivered to the output ports.