Research On Defected Ground And Transmission Line Based On Spoof Surface Plasmon Polariton

Spoof Surface Plasmon Polariton(SSPP)is a special type of electromagnetic wave different from conventional electromagnetic waves mode.SSPP can constrain electromagnetic energy at the interface of a medium,while decay rapidly in the vertical direction.In recent years,SSPPs have drawn extensive attention in microwave and Thz circuit design.And it is possible to effectively adjust the frequency characteristics of SSPP by changing the parameters and configuration of periodic SSPP unit.Based on SSPPs’various characteristics such as filtering,transmission,and radiation,filters,antennas and other devices can be constructed to realize high performance.Based on the summary of previous research results,this article continues to conduct in-depth research on the application of SSPP in microwave passive circuits.The main work is as follows:(1)A symmetrical dumbbell shaped defected ground structure loaded with SSPP is proposed,and an equivalent lumped circuit model is constructed based on its dual zero transmission characteristics.The intrinsic relationship between model parameters and the structure of SSPP was studied,and a 7-order low-pass filter was implemented based on this new structure.Simulation and test results show that the first zero of the dual transmission zeros can be used to sharpen the transition band of the low-pass filter with a steep transition band with a slope of 129.4 d B/GHz,and the second zero can be used to increase the out-of-band suppression of the low-pass filter with a suppression frequency of 0.97 GHz to 20.0 GHz.Moreover,due to the slow wave characteristics of SSPP,it can reduce the size of the filter to only 0.071λ_g~2.(2)An asymmetric dumbbell shaped defected structure ground loaded with SSPP is proposed.Based on its three zero transmission characteristics,an equivalent lumped circuit model is constructed.The intrinsic relationship between model parameters and the structure of SSPP is studied.Based on this new structure,Wilkinson and Gysel power splitters that can suppress multiple harmonics are implemented.Simulation and test results show that:The new structure can effectively suppress the three frequency points of the power divider.The degree of suppression for the three frequency points of the Wilkinson power divider is about-25d B for the 1.4 GHz,2.1 GHz,and 2.8 GHz frequency points,while the degree of suppression for the Gysel power divider is about-40d B for the first two frequency points,and about-25d B for the third frequency point.(3)The integration of microstrip SSPP transmission lines on flexible dielectric substrates was proposed.Two wearable SSPP transmission lines using fabric as substrate were realized using conductive fiber embroidery and liquid metal ink screen printing processes,respectively.The test results show that both transmission lines can effectively guide the transmission of surface plasmons.