Studies On Ceramic Microwave Absorber For Isolator Load In Ku-band

For the purpose of solving the current problem of microwave absorbing materials with poor integrated performance of the absorption loss and power-handling, which is not satisfied with the need of development on future microwave system, and the view of absorbing material’s design for load was put forward. This study introduced the traditional ceramic preparation technology into the preparation of the Isolator absorption load. The great thermostability and high breakdown voltage of ceramic were used to overcome the weaknesses such as low microwave absorption. Different ceramic absorbers for Isolator were fabricated by ceramic sintering process. The test results are as follows:Different ratio Co-Ti substituted BaM hexaferrites of Ba(CoTi)xFe12-2xO19were prepared by traditional ceramic method. The crystal structure and the morphology were characterized by XRD and SEM, respectively for all samples. The microwave absorbing abilities of samples were measured by the vector net-analyzer, The results showed that, no significant variations were observed in the microstructure characteristics with Co-Ti substitution, while the grain size and the absorption loss increased. The maximum loss value of-22.8dB at11.6GHz was observed for the x=1.0sample.For turning the magnetic resonance frequency and bandwidth of the reflection loss, different amounts of manganese (Mn) were incorporated into the BaCoTiFe10O19for the substitution of cobalt (Co), and then the BaMnxCo1-xTiFe10O19was obtained via the solid-state reaction method. Subsequently, the crystal volume expanded with increasing Mn2+substitution as confirmed by X-ray diffraction results. No significant morphology change could be found in the scanning electron microscope images when Co2+was partially substituted by Mn2+, but the coercivity and remanent magnetization raised as Mn2+increased. The complex permittivity and permeability were collected by the vector net-analyzer. The absorption peak shifted to higher frequencies with the substitution. The maximum loss value of-30.5dB at13.4GHz was observed for the x=0.6sample.The ferrite ceramics which were obtained via the solid state reaction and sol-gel powder preparation method and then adopt different sintering schedules were investigated, respectively. The results showed that the BaMnxCo1-xTi1.0Fe10O19ferrite ceramics with the solid state powder preparation method had the best sintering schedule for1200℃-8h, the microwave absorbing performance improved significantly. When x=0.6, the absorption loss of2.5to9.2dB/mm in frequency range of12to18GHz. The sample with x=0.8shows a maximum reflection loss of6.9to12.1dB/mm in frequency range of12to18GHz. In addition, the voltage breakdown strength of BaMnxCo1-xTi1.0FeioO19was measured. The results showed that, the voltage breakdown strength was decreased at first and then increased with increasing x. The voltage breakdown strength of undoped Ba ferrite is the largest. Based on the breakdown strength and absorption performance, BaMno.6Co0.4TiFe10O19may be a good candidate for isolator load absorbing material.