Fabrication of circulator with coplanar wave guide structure

A circulator with a coplanar wave-guide structure, whose external form is rectangular, was designed and analyzed by using a three-dimensional finite-element method. In this analysis, the nonreciprocal transmission characteristics with an insertion loss of 1.0 dB and an isolation of 33 dB appeared at around 7 GHz. The bandwidth defined as the band with isolation of over 20 dB was 50 MHz. A circulator was fabricated based on the design, and the transmission characteristic of the circulator was measured. The fabricated circulator showed an insertion loss of 4.9 dB and an isolation of 28 dB at around 8 GHz. The bandwidth at isolation over 20 dB was 70 MHz.