The Wilkinson design RF combiner is one of the most classic and widely used passive power splitting/combining components in the microwave and radio frequency industry, first proposed by Wilkinson in the 1960s. With its unique balanced circuit structure, it perfectly solves the contradiction between low insertion loss, high port isolation and good impedance matching, and has become the mainstream design scheme for medium and high-performance RF combiners. Different from simple resistive power dividers and branch-line combiners, the Wilkinson structure integrates transmission line impedance transformation and isolation resistance network, realizing efficient signal transmission and channel interference suppression at the same time, and is widely used in various civil communication, industrial testing and military RF systems.

The core structural feature of the Wilkinson combiner is the symmetrical two-stage transmission line and terminal isolation resistance design. Its internal circuit consists of two sections of 1/4 wavelength impedance transformation transmission lines and a high-precision isolation resistor connected between the two branch ports. In the signal splitting mode, the input signal is evenly divided into two paths of equal-amplitude and equal-phase signals through the symmetrical transmission lines, with extremely low power loss; in the signal combining mode, the two input signals are superimposed and output, and the isolation resistor can absorb the unbalanced signal component generated by the inconsistency of the two input signals, effectively suppressing signal reflection and crosstalk between ports. The whole structure realizes perfect impedance matching of all ports, and the VSWR of input and output ports is close to 1:1 in the operating frequency band.

The Wilkinson design combiner has outstanding comprehensive performance advantages. First, it has ultra-low insertion loss, far lower than resistive combiners, ensuring high-efficiency signal transmission; second, it has high port isolation, which can reach more than 20dB in conventional models and 25-30dB in high-precision models, effectively avoiding mutual interference between channels; third, it has flat frequency response and stable phase performance, suitable for wide-band signal processing. In addition, the structure has strong expansibility, which can be expanded from 2-way to 4-way, 8-way and multi-channel combiners through cascading design to meet different power distribution and synthesis needs. It is widely used in base station signal distribution, antenna feeding systems, RF signal testing equipment, wireless LAN systems and microwave communication equipment. Its simple structure, stable performance and low manufacturing cost make it the most cost-effective RF combiner solution, occupying a dominant position in the civilian RF device market, and also serving as the basic structural prototype for most high-performance customized combiners.