Designs Of Reconfigurable Devices And Bandpass Filters Based On Spoof Surface Plasmon Polaritons

In recent years,scientists have gained a deeper understanding of spoof surface plasmon polaritons,and their research and applications have become increasingly widespread.Spoof surface plasmon polaritons are artificially constructed through periodic structures to achieve electromagnetic waves with properties similar to those previously achieved by surface plasmons in the optical band.They have high surface localization and binding properties,low loss,dispersion characteristics,and low crosstalk to adjacent transmission lines.They have very broad application prospects in both microwave and millimeter wave and terahertz frequency bands.In this article,based on the topic of spoof surface plasmon polaritons,a reconfigurable transmission line,a reconfigurable leaky wave antenna and two types of bandpass filters are designed and tested.The main content of this article is as follows:1)A reconfigurable transmission line based on SSPPs was designed.Varactor diodes are loaded on SSPPs units to achieve reconfigurable cutoff frequency.The transmission line uses a gradient transition structure to achieve mode conversion between microstrip lines and SSPPs units.The transmission line has been processed,tested,and validated,and subsequent simulation optimization has been carried out.2)A reconfigurable leaky wave antenna based on spoof surface plasmon polariton is proposed.The antenna is fed by a coplanar waveguide,and the quasi TEM mode is converted to SSPPs mode by a gradual transition structure.Subsequently,variable capacitors are loaded onto the SSPPs unit to regulate its dispersion curve,and circular patch units are introduced near the SSPPs transmission line to achieve-1st order fast wave harmonics to realize effective radiation.The simulation results show that by adjusting the loading capacity value,a maximum fixed frequency beam scanning angle of 28 ° on the xoz plane and a fixed beam leaky wave radiation from 7.6GHz to 8.6GHz can be achieved.3)Two bandpass filters based on SSPPs first-order higher-order modes are proposed.First,a miniaturized SSPPs unit loaded with meandering lines is proposed.Then,in order to suppress the passband of second high-order mode,the unit structure is adjusted and optimized,and the surface current is analyzed.Then,the Filter design is designed with microstrip lines and trapezoidal transition structures.The filter is fabricated and tested.The test results proved that the passband from 5.08 GHz to 6.28 GHz is realized.The minimum insertion loss in the band is about 0.4d B,and the return loss is less than-10 d B.The group delay within the passband ranges from 0.6ns to 0.74 ns.Subsequently,in order to achieve single mode transmission within a wider frequency band,interdigital structures are loadet to suppress the fundamental mode passband.Microstrip lines and trapezoidal transition structures are also used to implement the filter.The test results showed that the passband from 6GHz to 6.3GHz is achieved,and the out of band suppression is greater than15 d B from 0 to 11 GHz.The return loss is less than-12 d B.Both filters have the advantage of compact structure.4)A millimeter wave controllable narrowband bandpass filter based on SSPPs that can be applied in the n258 frequency band is proposed.The dispersion curve of the double conductor SSPPs unit is analyzed,and two pairs of coupling branches are loaded on its structure.The equivalent circuit and dispersion curve of the double conductor SSPPs unit loaded with coupling branches are analyzed,and the influence of parameter changes on the ideal passband of the dispersion curve is explained.Then,in order to combine the actual test conditions,we used the grounded coplanar waveguide to feed and trapezoidal transition structures to realize mode conversion to make the performance of the filter better.We also analyzed the influence of parameters on the passband.Finally,processing testing is conducted,and the measured return loss is less than-13 d B.The insertion loss is 1.7d B,and the out of band suppression is greater than 20 d B.The passband bandwidth is 10.8%,and the group delay ranges from 0.43 ns to 0.56 ns.Measured results maintain good consistency with the simulation results.This design has the characteristics of narrowband and easy regulation.