A parallel connected Marchand balun using spiral shaped equal length coupled lines

This paper presents a 6-20 GHz broadband planar monolithic balun. To get a broadband characteristic without narrow spaced coupled transmission lines, a parallel connected Marchand balun with spiral shaped equal length coupled lines are used. A developed monolithic balun achieves the maximum insertion loss of 5 dB including 3 dB power splitting loss from 6 to 20 GHz.