Research And Design Of Slot Line-spoof Surface Plasmon Polariton Filter

Spoof surface plasmon polariton(SSPP)are surface waves that propagate near the metal-dielectric partition interface along a periodically inscribed slot.The microstripslot line conversion structure is a broadband filter structure.The slot line-SSPP filter consists of a microstrip-slotline conversion section and SSPP together,featuring high steepness and high out-of-band rejection,which also allows for convenient design of time-delay characteristics.The main work of this paper is as follows.1.For the microstrip-slotline structure used in the filter,an equivalent circuit model is established,and its bandpass characteristics are analyzed and calculated theoretically.For the cutoff and delay characteristics of SSPP used in the filter,the effect of SSPP cell size on its cutoff frequency is compared,and the factors affecting the SSPP delay are studied.2.The slot line-SSPP filter is designed.Compared with the conventional SSPP filter,the introduction of microstrip-slotline filter structure improves the steepness and out-of-band rejection of SSPP filter,the rectangular coefficient is improved from 1.63 to 1.37,and the out-of-band rejection is increased from 25 dB to 40 dB.3.The Post-Wall Slotline(PWS)-type slot line-SSPP filter is designed.Compared with the slot line-SSPP filter,the PWS is used to reduce the traditional slot line impedance,which subsequently reduces the requirement for the plate dielectric constant.This improves the application breadth of the filter without sacrificing performance.4.The study of slot line-SSPP filter time delay regulation.Two methods are proposed to change the time delay of the filter: changing the length of the SSPP transmission line and changing the cell structure of the SSPP.The advantages and disadvantages of the two methods are analyzed.In the time domain,the transmission characteristics of the filter designed in this paper are investigated,and its fidelity for broadband pulses is above 0.9 with excellent results.The slot line-SSPP filter designed in this paper is novel,featuring high steepness and high out-of-band rejection,and also allows for convenient implementation of the time-delay characteristics.