Chang, Je YaoJe YaoChangLo, Tsu YuTsu YuLoChen, Pin YenPin YenChenWei, Tan ZhiTan ZhiWeiHuang, Shih PingShih PingHuangTsai, Wei TingWei TingTsaiLiou, Chong YiChong YiLiouSHAU-GANG MAO2024-02-222024-02-222024-01-012079-9292https://scholars.lib.ntu.edu.tw/handle/123456789/639891The traditional rat-race coupler comprises a quarter-wavelength transmission line and a three-quarter-wavelength transmission line. In this design, the slow-wave structure transmission line is employed to replace the conventional quarter-wavelength transmission line, and the three-quarter-wavelength transmission line is substituted with the left-handed transmission line. By using the TSMC CMOS 90 nm fabrication process, a circuit is created with a chip size of 300 μm × 200 μm, corresponding to the electrical size at 39 GHz of 0.039 (Formula presented.) × 0.026 (Formula presented.). The measured results demonstrate that the operating bandwidth is 35 to 43 GHz, with an amplitude imbalance of around 0 dB, a phase error within 1°, a return loss of less than 26 dB, and an isolation better than 40 dB.composite right/left-handed transmission line | metamaterial | rat-race coupler | slow wave[SDGs]SDG7journal article10.3390/electronics130204172-s2.0-85183423412https://api.elsevier.com/content/abstract/scopus_id/85183423412