Branch-line coupler using planar circuits composed of triangular-patch and strip conductors.

A new configuration of inner conductor is presented in this paper for a planar branch-line coupler at high-frequency range where the linewidth is not negligible with respect to the guide wavelength. The high characteristic admittance lines with a wide linewidth deteriorating higher-frequency performances of the branch-line coupler are replaced with an equivalent planar circuit consisting of triangular patches and strip conductors. In this way, it is shown theoretically and experimentally that a 3-dB 90° hybrid is obtained in the high-frequency region in which the ratio of the width of the transmission line with a characteristic impedance of 50Ω to the guide wavelength at the center frequency is about 1.35 times that of the conventional case. © 2006 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 89(5): 1–8, 2006; Published online in Wiley InterScience (<URL>www.interscience.wiley.com</URL>). DOI 10.1002/ecjb.20240 [ABSTRACT FROM AUTHOR]