Research And Design Of Miniaturized Narrowband Filter

Since entering the new century,due to the fast development of relevant technologies in the aspect of wireless communication,higher requirements have been placed on the property of electronic equipment in communication systems.As an important part of the entire RF front-end,the main function of the bandpass filter(BPF)is to achieve signal selection and interference suppression,Therefore,the communication quality of the whole system is closely related to the filter property.For improving the performance and reliability of the entire communication system to achieve high-level communication,contemporary high-performance filters are developing towards wide stopband,compact size,and low radiation.In addition,out-of-band interference is also an important problem in modern microwave communication system.Wide stop-band filters can effectively suppress out-of-band interference and improve signal quality in communication system.At the same time,the design of wide stopband filter is also a research hotspot in recent years.In recent years,scholars have proposed a large number of high-performance filters with new structures to meet the requirements of RF front-end for miniaturized,wide stopband filters.This paper first introduces some professional theory related to filter design and the recently development situation of filters in the domestic and overseas,and then combines the practical application scenarios to discuss the necessity of designing filters with compact size and low radiation loss.Subsequently,it was found that filters based on defective ground structure(DGS)have the advantages of compact size and wide stopband,and combined with the actual demand,a new structure is proposed—fully-packaged substrate integrated defect ground structure(FP-SIDGS).In this paper,based on the T-type FP-SIDGS resonant unit and the E-type FP-SIDGS resonant unit,two high-performance filters are designed,and the two filters are simulated and optimized by combining traditional analysis methods with modern electromagnetic simulation software,which greatly improves the efficiency of filter design.The first filter is based on a T-type FP-SIDGS resonant unit.Its center frequency is located at 2.5 GHz,the minimum insertion loss in the passband is only 1.3 d B,and the bandwidth is 8%.In addition,its core size is only 13.8 mm×8.6 mm(0.217?g×0.135?g),the stopband is extended to 21.8 GHz(8.72 f₀),and the rejection level is higher than 26.4 d B.The second filter is designed and manufactured based on the E-type FP-SIDGS resonant unit.The final test results show that its center resonant frequency is 5.1 GHz,the 3d B bandwidth is 8.6%,the radiation loss is less than 1%from 0-18 GHz,and the stopband rejection range reaches 16.7 GHz,the rejection level is higher than 34.7 d B,and the core size 9.8mm×4.6 mm.