What's The Best Way To Achieve An Unequal Power Split?

By Doug Jorgesen

For RF and Microwave engineers, designing an unequal power split is a common yet challenging task with several solutions. Each method suits different frequency ranges, split ratios, and design setups, from surface mount and chip and wire to waveguide configurations. Pick-Off Tees, for example, offer simple implementation and are suitable for low-frequency splits (40 to 20 dB), though they lack directivity and have poor return loss for higher values. Resistive Power Splitters, which can achieve even higher splits (up to 40 dB), are better matched at low frequencies but incur additional loss on the main line.

Directional Couplers provide high performance with minimal insertion loss and high power handling, making them ideal for uneven splits between 30 and 8 dB, though they require precision in design and fabrication. Rat Race and Branchline Couplers and Wilkinson Power Dividers offer good isolation and match quality for near-equal splits but are limited in uneven division by achievable impedance values. Wilkinson dividers, in particular, are a preferred choice for broadband applications but become challenging to implement for higher uneven split ratios.

Explore how Quadrature Hybrid Couplers combine high isolation with DC isolation and are robust, though they come with higher loss than Wilkinson dividers. Choosing the appropriate method depends on the specific split requirement, desired bandwidth, and available design resources.