Design and analysis of low temperature co-fired ceramics ferrite circulator

The S-band low temperature co-fired ceramics (LTCC) ferrite circulator was designed and analyzed based on multilayer chip structure, and the effect of some key problems in the preparing process on the frequency characteristic of the LTCC ferrite circulator was investigated by simulation method. The results show that the LTCC ferrite circulator with hybrid structure, which consists of microwave ferrite layer, ceramic dielectric layer and three-dimensional matching circuit, can provide excellent in-band performance. The cylindrical conductor connects two impedance lines in the three-dimensional wiring circuit of the LTCC ferrite circulator. It is found that the transmission and isolation characteristics of the LTCC ferrite circulator deteriorate rapidly, when the height of port air gap under cylindrical conductor reaches 20 m. In order to resist the significant reduction of the transmission and isolation characteristics, the air gap between microwave ferrite layer and ceramic dielectric layer should not be more than 20 m. Consequently, the matching co-firing between cylindrical conductor and ceramic dielectric layer, and between microwave ferrite layer and ceramic dielectric layer is extremely important to ensure excellent performance of the prepared LTCC ferrite circulator.