| 5G communication is the most advanced communication technology at present.Sub-6GHz belong to the 5G band adopts multi-antenna MIMO technology,which is a key technology that will bring about a surge in the number of channels.Therefore,a great deal of filters need to be integrated into the antenna,which requires filters with low insertion loss,low cost,light weight,high suppression and other characteristics.Compared with metal waveguide filters,some new type of dielectric filters made of high dielectric constant ceramic materials without external cavities have great application prospects in5 G base station RF modules due to their small size,superior temperature stability,high Q value and low production cost.This paper mainly studied the transmission performance of band-pass ceramic dielectric filters with a frequency of 3.5GHz and a passband range of 3.4GHz?3.6GHz.In this paper,four types of dielectric filters with different structures were designed based on the coupling matrix and two of them were processed and tested.This paper mainly carried out the following work:1.Based on the cross-coupling theory,single-layer six-cavity and single-layer eightcavity ceramic dielectric filters were designed and tested respectively.The CQ topological structure was adopted to generate a couple of transmission zeros at both ends of the passband.The coupling matrix was obtained by the filter synthesis software,the coupling coefficient and external Q value were calculated by using the dual-mode extraction method and the group delay method.The inductive coupling structure was achieved by diaphragm and diaphragm + blind hole,the capacitive coupling structure was achieved by deep blind hole,the input and output coupling was achieved by 50 ? coaxial connector.2.In this paper,two ceramic dielectric filters were designed particularly.So as to improve the ability of remote harmonic suppression,the strip line low-pass filter circuit was integrated on the external PCB board.Through the establishment of the co-simulation model,the simulation optimization can reduce the interpolation loss deterioration to0.4d B,and the harmonic suppression at the far end of the band can reach more than 30 d Bc,which can meet the target requirements of the 2-10 GHz frequency band.Based on different excitation types,a surface-type double-layer six-cavity dielectric filter was designed in this paper,which uses U-shaped input and output electrodes to feed in and out electromagnetic waves.Coupling Windows are used between upper and lower resonators: perceptual coupling Windows distributed at the edge and capacitive coupling Windows distributed at the center.The surface-type dielectric filter is beneficial to system miniaturization and system integration.3.Based on the existing metallization process,the influence of the metallization film on the performance of the dielectric resonant single cavity was simulated and analyzed by setting different layered impedance boundary conditions using the soldering mode,the multilayer metal film system of transition layer,conductive layer and welding layer was put forward,which was of great significance to practical engineering.4.With the help of filter synthesis software,parameters were extracted and modified information was provided to achieve the purpose of auxiliary optimization.The tuning test was carried out by polishing the silver layer strategy,and finally the measured filter can meet the requirements of various performance indicators,and all had a certain amount of allowance. |
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