Directional coupler composed of CoFeB metallic magnetic film/polyimide dielectric film hybrid transmission line

This paper describes a novel thin film type directional coupler using magnetic/dielectric hybrid transmission line device. The hybrid transmission line with a dielectric/magnetic/dielectric sandwich structure has a large effect of wavelength shortening. As a result of signal characteristics evaluation, the directivity of the signal in the device was higher than 18 dB, and insertion loss was less than 0.6 dB at the operating frequency of 0.8/spl sim/2 GHz of the cellular phones.