With the development of the fifth and sixth-generation mobile communications, there is a growing demand for high data throughput, low latency, and high-quality service for multiple users simultaneously. This has driven operating bands towards millimeter wave (or terahertz), which offer a large bandwidth to support these requirements. To this end, our group has focused on developing low-loss millimeter-wave components and multifunctionally reconfigurable intelligent surface (RIS).

Due to the increased frequency, various loss factors, such as conductor, dielectric, and propagation losses, has become more significant, resulting in increased design challenge. Therefore, low loss is considered to be one of the most important advantages for millimeter-wave hardware designs, contributing to relaxed highgain requirement of power amplifiers or antenna arrays. Our group has developed a variety of miniaturized, low-loss, multi-band or differential mm-Wave (28/39 GHz) components based on the substrate-integrated waveguide (SIW) or integrated-passive-device technology. Besides, these components are easily integrated with active/passive circuits.

The sixth-generation mobile communications depend on deploying a smart radio environment, exploiting software-reconfigurable entities to optimize the wireless environment and ensure uninterrupted communication services for improved quality of service. Reconfigurable intelligent surface (RIS) can be regarded as one of such solutions to achieve an intelligent radio environment. Through integration of heterogeneous networks, robust communications can be supported. Therefore, our group has developed various multifunctional RIS solutions in the X/Ku bands, featuring wide-angle/multi-beam scanning, switchable polarization, multi-frequency/wideband capabilities, and filtering responses. By tuning their operating modes, they can adapt to a variety of application scenarios.

▶[1] P. -L. Chi, H. -T. Shih, and T. Yang, "5G millimeter-wave substrate-integrated waveguide quad-channel diplexer with high in-band and wideband isolation," in IEEE Microwave and Wireless Components Letters, vol. 31, no. 6, pp. 650-653, June 2021. (Link)
▶[2] P. -L. Chi, Y. -M. Chen, and T. Yang, "Single-layer dual-band balanced substrate-integrated waveguide filtering power divider for 5G millimeter-wave applications," in IEEE Microwave and Wireless Components Letters, vol. 30, no. 6, pp. 585-588, June 2020. (Link)
▶[3] J. Hu, P. -L. Chi, and T. Yang, "Novel 1-bit beam-scanning reflectarray with switchable linear, left-handed, or right-handed circular polarization," in IEEE Transactions on Antennas and Propagation, vol. 71, no. 2, pp. 1548-1556, Feb. 2023. (Link)