Jeonbuk National University (JBNU) Graduate School, Division of Electronics and Information Engineering master's student Geun-hoe Lee (Advisor: Yong-chae Jung) proposed a next-generation RF coupler design technique that secures wide bandwidth and high design freedom with a reduced number of components, and won the Excellent Paper Award at the '2026 Korean Electromagnetics Society Summer Conference'.

The Korean Electromagnetics Society Summer Conference is a leading domestic academic event for sharing the latest technologies and research outcomes in the field of electromagnetics. This year's conference, under the theme 'Eyes on the Quantum, a Door to Space: Electromagnetic Technologies', broadly covered electromagnetic technologies and research trends in 5G-Advanced and 6G wireless communications as well as space, satellite, defense, medical, and industrial fields.

At the conference, Geun-hoe Lee gave an oral presentation titled 'Branch-Line Hybrid Coupler Based on Arbitrary Termination Impedances Using Cross-Resonant Circuits,' receiving recognition for the originality and technical maturity of the research.

The core of the study is a new branch-line hybrid coupler structure that employs cross-resonant circuits to allow different termination impedances. By integrating LC resonant structures inside the circuit, the design secures a wide operating bandwidth while using fewer inductors than conventional lumped-element approaches. It also increases design freedom by enabling different termination impedances to be applied at each port.

In addition, a parallel LC resonant circuit was added so that the bandwidth could be expanded while maintaining the operating characteristics of conventional couplers at the center frequency. The design can be optimized to meet required circuit specifications through design coefficients.

The branch-line hybrid coupler is a key circuit for power division and phase control in wireless communication transmit/receive systems. The research outcomes can be applied to power dividers, phase shifters, and balanced power amplifiers that must connect RF circuits with different impedances.

Especially in RF integrated circuit (IC) environments where miniaturization is important, the proposed structure can implement circuits with fewer components than conventional structures while securing wide bandwidth and high design freedom. It is expected to be applicable to various high-frequency wireless communication systems, including 5G-Advanced and 6G.

Geun-hoe Lee said, 'Through this research, I confirmed a new design possibility for branch-line hybrid couplers that allows various termination impedances within a limited area. I will advance the research by validating the applicability of the proposed structure through actual RF IC fabrication and measurements, and by developing it for application in diverse wireless communication systems.'

Meanwhile, this research was carried out with support from the National Research Foundation of Korea's Major Research Center Program and the Regional Intelligent Innovation Talent Program, funded by the Ministry of Science and ICT and the Ministry of Education.