Design of Wide-Band Branch-Line Coupler in the G-Frequency Band

This paper deals with the design of broadband hybrid coupler in thin film microstrip (TFMS) technology for millimeter-wave applications in the G-band frequency range. The couplers to be designed are realized in BCB-based technology. The technological process as well as transmission lines characterization and optimization in term of attenuation are described. Classical 3-dB branch-line coupler is developed with 180-GHz central frequency. Then, based on this topology, a broadband coupler using series matching networks is developed. Such a topology allows to reach bandwidth over 50 %, with very flat coupling. Measurements performed in a wide frequency range up to 220 GHz attest from the design accuracy as well as the technological process quality