Synthesized Crystal Structure and Microwave Characteristics in Bandpass Filter of Dielectric Resonator Ba₂Ti₉O₂₀ Ceramics

Author: Hsiu-Fung Cheng(Department of Physics, National Taiwan Normal University)

Abstract：

An evanescent bandpass filter with resonance frequency f₀=5.10 GHz and band width Δf =0.0345 GHz has been designed for testing the feasibility of using Ba₂Ti₉O₂₀ materials as dielectric resonators. The width of the rectangular cavity was found to af-fect the cutoff frequency of the device most significantly, while the length of the cavity has least influence. The insertion of the dielectrics, on the other hand, lowers the cutoff frequency. The center frequency of the passing band is the same as the resonance fre-quency of the dielectric resonators. As to the synthesis of the materials for dielectric resonators, i.e., Ba₂Ti₉O₂₀, the sprayed pyrolysis of metallo-organic precursors was found superior to coprecipitation process. The formation of intermediate phases, i.e. BaTi₄O₉, BaTi₅O₁₁, found in coprecipitation process can be completely eliminated by sprayed pyrolysis technique.

Keywords：Microwave bandpass filter, Dielectric resonator, Ba2Ti9O20

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