Research On Ultra-Wideband Band-Notched Filters Based On Defected Ground Structures

Ultra-wideband wireless communication technology is active on historical stage of wireless communication industry because of its abundant GHz-class scarce frequency resources.With the rapid development of wireless communication field,higher requirements for the anti-interference ability of UWB(Ultra-wideband,UWB)systems have been put forward,so the research of UWB notch filter is one of the development cores in this field.This paper will make full advantage of the metal floor structure of UWB filter and discuss how to use the DGS(defected grounding structure,DGS)to realize the frequency shift of single-notch band in the full frequency band,and characteristics of multiple notch bands,single wide notch band,dual wide notch bands and high stop-band.The main contents are as follows:Firstly,aiming at optimization time consuming problem of electromagnetic simulation,based on space mapping theory,an electromagnetic-synthesis space-mapping method is proposed.This method solves the problem from many aspects,such as effective control of key parameters'quantity,high efficiency of optimization target and dimension reduction of mapping relation,which effectively reduces the optimization time,and provides an optimization method for the follow-up research of UWB notch filter.Secondly,aiming at frequency shift problem within whole passband of UWB system,based on fractal DGS,a design method about UWB filter with single notch band is proposed.This method,on the basis of the Sierpinski fractal theory,puts forward the improved "Y" type defect structure,solves the problem from the perspective of transforming spatial characteristics into electromagnetic characteristics.Through third-order fractal iteration,the center frequency of single notch band is moved within the range of 4.08GHz?10.04GHz,the maximum attenuation in the notch band is more than 20dB,and the design of single notch UWB filter with full-band frequency-shift is realized.Three UWB filters with single notched band are optimized by the electromagnetic-comprehensive space-mapping method,whose measured results are basically consistent with its simulation results.Thirdly,aiming at broadband interference problem within passband scope of UWB system,respectively based on the open-loop DGS and the coplanar spiral DGS,single/dual wide notch-band UWB filters are proposed.This method solves the problem from two aspects:coplanar UWB filter and double-faced UWB filter,realizes wide notch band through strong coupling characteristics among several DGS units with the same size,realizes dual wide notch band through two groups of DGS resonant units with different sizes.Single/dual wide notch-band UWB filters are realized,whose bandwidth of wide notch band can reach up to 2.04GHz under 10dB attenuation.Four UWB filters with single notched band are optimized by the electromagnetic-comprehensive space-mapping method,and obtained the target filters whose measured results are basically consistent with its simulation results.Fourthly,aiming at multiple frequency interference problem within whole passband of UWB system,respectively based on the open-loop DGS and the coplanar spiral DGS,UWB filters with multiple notch bands are proposed.This method also solves the problem from two aspects:coplanar UWB filter and double-faced UWB filter,realizes the adjustment from single notch band to five notch bands through multiple sets of DGS units with different sizes.The design of UWB filters with multiple notch bands are realized,among them,in double-faced UWB filter,the high stopband characteristics are realized by introducing two groups of arc-ring DGS,whose high stopband frequency under 15dB attenuation can reach at least 20GHz.UWB filters with multiple notch bands are optimized by the electromagnetic-comprehensive space-mapping method,and obtained the target filters,whose measured results are basically consistent with its simulation results.