Research On Microwave Devices Based On Spoof Surface Plasmon Polaritons

Surface Plasmon Polaritons(SPP)are electromagnetic waves with unique properties in the optical band that can bind energy to the conductor surface.Spoof surface plasmon polaritons(Spoof SPP,SSPP)is concrete embodiment of applying SPP to the THz and microwave bands by constructing periodic structures.The geometric parameters of the structure which can excite SSPP affects its dispersion characteristics and therefore has far-reaching implications for building tunable devices and circuits.This paper focuses on the complementary slot periodic structure and its application in the waveguide,filter and leaky wave antennas working in microwave frequency band.Firstly,the effect of the shape and size of the complementary gap structure on the SSPP dispersion curve is discussed.The analysis of the groove depth is the most important influence factor.Then the size of the unit structure is determined.The trapezoidal structure coplanar waveguide is used for feeding,and then the trench depth gradient periodic structure is used to realize the transition and momentum matching of CPW guided wave to SSPP wave.At the same time,the fractal structure is applied to the complementary gap structure to improve the performance of SSPP waveguide.The designed waveguide has a wider bandwidth and a higher transmission efficiency.Then,based on the SSPP waveguide,the split ring resonator is loaded to acquire the band stop function.Combined with the characteristics of complementary gaps,a built-in bilateral U-shaped SRR structure is proposed.We analyzed the effect of its line width and the length of the bottom edge of the U-shaped groove on the resonant frequency.The dual-band band-stop filtering function is implemented by changing the SRR width,and then two SRR rings are loaded to optimize the transmission characteristics at the resonance frequency.The built-in SRR structure enables band-stop filtering without increasing the waveguide width.Finally,the SSPP is combined with the theory of the leaky wave antenna to open the gap between the periodic structures to realize the SSPP leaky wave antenna based on the open radiation.The dispersion curve of the cell structure after slotting is analyzed,and the gap between the SSPP mode and the radiation mode is realized by the gap of the width gradient.Considering the size of the dual-port antenna is too large,a single-port antenna is also designed to discuss the effect of miniaturization on the working frequency band and gain of the antenna.The SSPP leakage wave antenna realizes the frequency sweep function.For this,we discuss the relationship between the operating frequency of the antenna and the direction of the main lobe.