Research And Design Of 5G Ceramic Filters And Multiplexers

As our country's mobile communication technology enters the 5G era,5G base stations have entered the process of large-scale construction.With this trend,RF and microwave frequency selective devices such as filters and diplexers are key passive components in base stations,and their design requirements keep improving.Due to the substantial increase in the number of channels in 5G base stations,the number of frequency selective devices such as filters and diplexers in a single base station has also increased exponentially.In order to reduce the circuit complexity of the base station and improve the performance,people have raised more stringent requirements on the filtering characteristics,size,weight,in-band loss,and heat dissipation of the base station filter and multiplexer.This thesis studies the practical problems encountered in the application of the current filter components in 5G base stations,and explores methods to improve device performance and improve practicability.The main research contents of the full text are as follows:Firstly,this thesis analyzes the pain points encountered in the design of filters,diplexers and other RF and microwave frequency selective devices in 5G base stations and the corresponding solutions.Clarifies the practical problems faced by these solutions in the application.Extensively investigated the current research status at home and abroad.Secondly,the synthesis process of the traditional single passband filter is derived by formulas in this thesis.As a comparison,a single passband filter synthesis method based on numerical iteration is introduced.Based on this method,the synthesis procedure of a filter is carried out.The simulation design,physical processing and debugging of the filter are guided according to the synthesis result.Both results and physical test results can meet the targets.In addition,the synthesis method of multiple passband filters based on numerical iteration is derived on the basis of single passband synthesis.Subsequently,this thesis introduces the design method of dual-mode filter based on dielectric waveguide,including resonant cavity design,intracavity inter-mode coupling structure design and inter-cavity coupling structure design.Aiming at the problem of harmonic interference of dual-mode filters,this thesis proposes a method that use ceramic material with different dielectric constants to fill the waveguide resonant cavity and reasonably configure the resonant cavity size to obtain a combination of resonant cavities with the same main mode frequency but different high-order modes frequencies.A filter based on the combination of resonators can be cascaded to obtain harmonic suppression.An example of a dual-mode filter designed based on this method and a traditional dual-mode filter design example are given in this paper.The simulated broadband frequency response of the two filters is compared to verify the effectiveness of the method for harmonic suppression.Next,this article introduces the synthesis method of the diplexer.In view of the problem that the dielectric waveguide diplexer is difficult to achieve a large coupling bandwidth at source,a common cavity type combination structure based on a quarter-wave coaxial resonant is proposed.On the basis of this structure,an improved combination structure that can simultaneously realize the large coupling between cavities across layers is obtained by introducing a curved waveguide.Based on these two structures,design examples are given.One of the examples is manufactured.The measured results are in good agreement with the simulation results,which verifies the effectiveness of the design.Finally,this article introduces a synthesis method for complex filter devices connected in parallel with multiple channels.First,it introduces the synthesis method of the single-pass band filter connected with frequency-dependent complex impedance,then gives the calculation method of the port complex impedance under the condition of multi-channel parallel connection.At the same time,in order to solve the problem that the curve fitting is wrong when the channel filter is synthesized,a method to improve the fitting accuracy of the corrected solution by increasing the order and screening the zero points is proposed.Based on the method introduced in this article.A number of synthesis examples are given in this paper to verify the effectiveness of the method.