Design And Research Of Microwave Bandpass Filter Based On Ceramic Dielectric Waveguide Resonator

As the core component of the RF module of base station,filters assume the role of screening the specific frequency signal effectively.In the era of 5G,the demand for filters is increasing dramatically due to the widespread use of Massive MIMO(Massive Multiple Input Multiple Output)technology.Based on this background,the traditional filter based on metal cavity structure will increase the windward area and load capacity of base station towers,which is not conducive to industrial applications.Therefore,it is of great research significance and engineering application value to effectively carry out the research of miniaturization and lightness of base station filters.Compared with the traditional metal cavity filters of base station,the ceramic dielectric waveguide filters are smaller and lighter while maintaining their operational performance.Thus,ceramic dielectric waveguide filters are expected to become the mainstream design solution for base station filter circuits in the 5G era,considering the design requirements of miniaturization,lightness and high selectivity.However,the current design system of ceramic dielectric waveguide filters is not yet perfect and the problem of difficult suppression of high-order harmonics still needs to be solved.Given that,based on the ceramic dielectric waveguide resonator,the design of the ceramic dielectric bandpass filter is carried out in this paper.At the same time,how to improve the out-band suppression performance of the filter is also studied.Four bandpass filters based on ceramic dielectric waveguide resonators are proposed.The following are the details of the study:1.The research background of ceramic dielectric waveguide filters is described and the research status at home and abroad is analyzed and the research goal of this paper is defined,further clarify the research objectives of this article.Based on the filter design index,the design of the ceramic dielectric waveguide filters is carried out combined with the microwave network theory and the coupling matrix synthesis theory,and the design procedure and scheme of the ceramic dielectric waveguide filter are determined.Moreover,the performance of out-band suppression is also studied.2.A design scheme of a sixth-order generalized Chebyshev bandpass filter based on ceramic dielectric waveguide resonators is proposed and validated.The design of a sixth-order bandpass filter based on ceramic dielectric waveguide resonators is proposed.The coupling topology and the coupling matrix of the filter are obtained according to the design indexes.The size of single cavity of the sixth-order filter is calculated and then the model is built and simulated.The simulation and measurement results show that the designed sixth-order bandpass filter feature good in-band selectivity and out-band suppression.To further improve the out-band suppression performance of the designed filter,without affecting the transmission of the dominant mode TE₁₀₁ mode,the suppression of the high-order modes TE₁₀₂ and TE₂₀₁ is realized by optimizing the position of the resonant cavity coupling window through in-depth analysis of the electromagnetic field distribution characteristics.The simulation results show that the out-band suppression covers 1.81 times the center frequency referring to the-15 d B suppression standard.3.A design scheme of a eighth-order generalized Chebyshev bandpass filter based on ceramic dielectric waveguide resonators is proposed and validated,and the design cycle is similar to that of a sixth-order filter.Simulation results show that the designed filter in this paper has high selectivity.At the same time,the out-band suppression of the designed eighth-order bandpass filter covers 1.6 times the center frequency referring to the-15 d B suppression standard,which is improved compared to the previous sixth-order bandpass filter.In order to further improve its out-band suppression performance,an improved stepped impedance lowpass filter has been designed in this paper.The out-band suppression performance of the band-pass filter is improved by cascading the lowpass filter and bandpass filter.Simulation results show that the out-band suppression covers 3 times the center frequency referring to the-15 d B suppression standard.