Design Of Compact Microwave Filter Based On Resonant Cavity

With the advent of the 5G era,the available communication frequency-band resources have been very limited,and the working frequency has been increasing.To be able to transmit signals between narrow passbands,there are strict on filter's power capacity and loss.The cavity filter's insertion is so low and the power capacity is so large that can be suitable for the technical requirements greatly.Moreover,the installation space is so limited that the requirements for the size of the filter is strict.Therefore,the study of a compact microwave filter based on a resonant cavity is of great application value.The topic of this artical is mainly carried out the project of compact microwave filter based on resonant cavity,which is derived from the fundamental microwave cavity,the knowledge of electromagnetic disturbance and tuning principle.The size of the filter is reduced by using dielectric and capacitor loading.And we designed a band-pass dielectric cavity filter.This article mainly includes the following tasks:1.There is a brief presentation of the evolutive researchful history of cavity filters.Then we studied the relevant theories of filters.The alumina dielectric coaxial cavity filter designed in this article is proposed on these foundations.2.According to the theory of resonant cavity structure,there is a analysis that the relationship between cavity's various parameters and its local quality factor.According to the principle of low-pass prototype circuit and coupling,we can caculate the order of the filter and the coupling system between the cavities of the filter.In the line with the transformation from low-pass to the band-pass prototype circuit,the coupling structure of the resonator filter is gradually designed and simulated by the method of inductive diaphragm.We also analyzed the influence of various parameters on the center frequency and coupling coefficient to determine the size of the filter structure.3.Based on the theory of dielectric resonators combined with the advantages of dielectric ceramic materials,we have explored the ceramic firing process.It is to use a sintering furnace to prepare ceramics at room temperature and pressure.We have conducted many experiments and compared the fired samples with engineering fired ceramics to further optimize the process.4.Based on the analyzation of the influence of the medium on the size,we designed and simulated a filter based on ceramic medium,which further reduce the size of the filter.Based on the poor adjustability of ceramic materials,we designed an adjustment structure Then,we simulated and optimized the overall structure of the dielectric filter in CST.Finally,a 10-order bandpass filter with a passband of 2515MHz-2675 MHz,an out-of-band suppression greater than 36 d B,and a size of only 48.75mm*18.3mm*5.87 mm was created.The coaxial cavity compact dielectric microwave filter is based on practical applications,which can be miniaturized when its permittivity is small.Meanwhile,its power volume is big enough.It can be used in base stations and other scenarios which is strict with the cavity's power and size.Moreover,the cavity is simple in structure and has a lower cost in manufacturing.