Design And Implementation Of The Miniaturized Cavity Filter

Cavity filter is a frequency selection device widely used in the front end of base station communication,which has high Q value,high power,low loss characteristics,compared with other types of filter are still having the effect that cannot replace.With the rapid development of communication system and the continuous improvement of people's demand for high-quality,high-speed,and large-capacity communication,the front end of the base station communication devices are more towards the miniaturization,integration,high performance,especially in the advent of the era of 5G,to further promote the development of miniaturization of the cavity filter process.Although in recent years has emerged more about the document of cavity filter miniaturization design,but on average,the biggest difficulty mainly embodied in the miniaturization of filter is the reliability of the mass production.Therefore,it is valuable to discuss the miniaturization design of cavity filter from the aspects of reducing sensitivity,increasing its tunability,reducing its processing difficulty and improving its simulation efficiency.This article is from these points to study the design and implementation of miniaturized cavity filter.Firstly,the main components of the cavity filter are analyzed from the resonant cavity and the coupling structure.After analyzing the methods of miniaturization design of different resonators,two new types of coupling structures are proposed based on the characteristics of common coupling structures,and the advantages of these two structures in the design of miniaturized cavity filters compared with traditional structures are analyzed.Secondly,a scheme to further reduce the volume of the filter by means of cover plate welding is presented,that is,the encapsulation of the filter cavity and the cover plate adopts the welding method,effectively reducing the thickness of the outer wall of the cavity body,thus further reducing The volume of the filter,The welding process of the cover plate was briefly introduced in the later stage.Thirdly,an optimization method based on Y parameter extraction and circuit co-simulation is introduced.The method combines the method of "field road" to simulate the filter and improve the simulation efficiency,the related theoretical formulas and specific simulation steps of Y parameter extraction are given.Finally,a cavity filter with an overall size of 65 mm×20 mm×15 mm was designed and implemented by making full use of the mentioned structural schemes,simulation method,and packaging process.The simulation and measurement results show that the filter in the pass-band of 3.4 ~ 3.6 GHz is less than 1.6 dB insertion loss and return loss is greater than 18 dB,and introduces two outside pass-band transmission zeros,has good features outside the band.At the same time,the filter also has the characteristics of small size,good tunability,easy processing,which satisfies the design requirements of the base station miniaturization filter.