Design of Diplexer Using Chip Components Considering Parasitic Elements

In this paper, we propose a design method for a diplexer composed of chip filters and components. This method is based on matching conditions that include parasitic elements of the chip components. It also introduces complex input admittances of the chip filters in the theoretical design for improving the matching conditions of the filters themselves. Therefore, the method is suitable to design a compact diplexer with low insertion losses in high‐frequency bands. A diplexer for 2.4 and 5 GHz is designed to verify the proposed method. The prototype achieves both low insertion losses and steep cut‐off characteristics. © 2026 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.