Design Of Microstrip Filter Based On Folded-step Impedance Resonato

The research of modern wireless communication technology is developing towards diversification and high standard,which makes communication equipment move forward to miniaturization,high performance and easy integration.Filter,as a device to complete frequency selection,mainly determines the selectivity and out of band anti-interference ability of communication system.Because of its more compact structure,Stepped impedance resonator(SIR)is often used in the design of various filters.However,the traditional step impedance resonators still have the defects of insufficient integration and poor performance,so this paper designs three kinds of highly integrated filters by using the folding deformation of step impedance resonators to apply to the current communication technology environment.Based on the traditional SIR,three new resonator structures are proposed.The dual-mode resonator structure of step impedance branched-loaded folded SIR makes the filter more miniaturized and has excellent high-frequency stopband suppression ability.The three-section SIR is bent and folded inward to form an embedded open ring,and the resonator structure loaded with open branches makes the overall structure highly integrated and the tuning parameters more abundant;In order to make the design of the filter compact,a fan-shaped step impedance branch loading multi-mode resonator is proposed in this paper.The low impedance branch in SIR is changed into a fan-shaped structure,and multiple fan-shaped branches are loaded.It is not only small in size,but also has good upper stopband characteristics.The three kinds of resonators are symmetrical in structure,and their resonance characteristics can be analyzed by using odd-even mode theory to simplify the design process.Three kinds of filters are designed.The structure of the dual-mode resonator enables the filter to be applied in the EHF band of 43-47 ghz.Two folded three-section SIR electrical coupling cascades form a four-way band filter with independent center frequency and controllable bandwidth.Eight transmission zeros are introduced,and each pass band has high isolation and selectivity.Different from the traditional uwb implementation structure,the fan-shaped SIR multi-mode resonator structure adopted in this paper can flexibly adjust the broadband of the filter to 3-10.6GHz,and the stopband can reach 16 GHz.