Research And Design Of High Performance Microstrip Bandpass Filter

With the innovation and development of wireless communication technology,people have higher and higher requirements for wireless communication systems.As the key signal filter in wireless communication system,the filter is making progress toward higher performance with lower insertion loss and higher return loss.Based on the background above,this paper carries out the research and design of highperformance microstrip band-pass filters in c-band and x-band.The main research contents are as follows:(1)First,this article introduces the microstrip line theory,analyzes the basic characteristics of the stepped impedance resonator(SIR),and uses a pseudo-interdigital SIR structure to design a single-band microstrip bandpass filter,and then uses simulation software HFSS models the filter to obtain the frequency response.The center frequency of the filter is 5 GHz,the 3 d B fractional bandwidth is 14%,the passband insertion loss is 0.27 d B,and the return loss is 37 d B.In addition,a narrow-band band-pass filter is designed by using cascade SIR structure.The central frequency of the filter is 5.2GHz,the 3 d B fractional bandwidth is 6.7%,the insertion loss of the band-pass is 0.18 d B,and the return loss is 23.3d B.Both of the above single-band bandpass filters have the advantages of high selectivity and low insertion loss.(2)In light of the requirements of the high performance and multiband,and the status quo of more meticulous frequency dividing,This article analyzes the basic characteristics of the stub-loaded resonator(SLR)structure,and uses a cascaded SLR structure to design a dual-band band-pass filter.The center frequencies of the two pass bands of the filter are 7GHz and 9GHz respectively,corresponding insertion losses are 0.53 d B and 0.36 d B,return losses are 25.2d B and 19.3d B,and the 3 d B fractional bandwidth are 6.7% and 3.8%.In the mean time,a dualfrequency band band-pass filter was designed by SIR,which was loaded with short-circuit branch lines of cascade structure.Its central frequency are 5.64 GHz and 8.5 GHz,and the corresponding insertion loss are 0.94 d B and 0.31 d B,return losses are 21.9 d B and 21 d B,and the 3 d B fractional bandwidth are 4.6% and 5.8%.Both of the above dual-band bandpass filters have the advantages of high selectivity and low insertion loss.