Compact Profile Filter Based On Spoof Surface Plasmon Polariton And Substrate Integrated Waveguide And Its Dynamic Regulation

Spoof Surface Plasmon Polariton(SSPP)is a type of electromagnetic surface wave propagating on sub-wavelength periodic metal groove structures in microwave and terahertz frequency ranges.It exhibits similar dispersion characteristics to the optical surface plasmon polaritons and shows promising advantages of local field enhancement and non-diffraction limit.Substrate Integrated Waveguide(SIW)is a planar waveguide structure similar to the classic rectangular waveguides.It retains the advantages of rectangular waveguides,such as low transmission loss and high transmission efficiency,and overcomes the disadvantages of rectangular waveguides,such as large volume and high integration cost.SSPP and SIW have high cut-off and low cut-off responses,respectively,whose cut-off frequency can be tailored to the structural dimensions.In this case,flexible band-pass filters can be designed accordingly to meet different demands by combining the high-pass characteristics of SIW with the low-pass characteristics of SSPP,which have found important applications in microwave and millimeterwave circuits.However,the reported SIW-SSPP hybrid filters have broadband width as the upper and lower cut-off frequencies of SIW and SSPP are far apart in the hybrid filters.On the other hand,as a passive structure,the bandwidth and filtering performance of the hybrid filter is fixed after design.In other words,its transmission characteristics are static,and changing its filtering performance requires redesigning the device,which to some extent limits the applications of hybrid filters in modern communication environments with limited spectrum resources.Based on these two considerations,this paper designs a novel SSPP structure to increase its equivalent length so that the upper and lower cutoff frequencies of the SIW-SSPP hybrid filter are close to each other to achieve narrow bandwidth.Furthermore,this paper introduces graphene as a dynamic excitation on the SSPP structure to dynamically control the SIW-SSPP hybrid filter by sweeping the graphene conductivity.The main research content is as follows:1.Proposed a miniaturized narrowband filter based on the SIW-SPP hybrid structure.Novel I-shaped SSPP grooves are designed to increase the effective length of the SSPP groove and reduce the upper cutoff frequency of the hybrid filter,which makes the cut-off frequencies of SIW and SSPP close and minimizes the bandwidth.Unlike the traditional wideband hybrid filters,the main mode of SIW in the passband close to the cut-off frequency is a class of quasievanescent wave,eliminating additional transitional SSPP grooves.This greatly reduces the lateral dimensions of the device,achieving miniaturization.Test results show that the designed filter has an insertion loss of 1.5 dB at 29.3 GHz,a narrow 3-dB bandwidth of 3%,and a miniaturized device size of 0.7λ × 0.38λ.2.Proposed a graphene-based dynamic control method for SIW-SSPP hybrid filters.By covering graphene on the surface of SSPP and sweeping the graphene conductivity,the structure of the hybrid filter can be re-configured,which correspondingly changes the SSPP upper cutoff frequency for bandwidth control.In DC tests,the switching on/off ratio of graphene is aslarge as 9.In the dynamic control test of the filter,the filter bandwidth changes from 8%to 46%,and the amplitude modulation at 30 GHz is as large as 20 dB.Under a bias voltage from-0.5 V to 1 V.