Research On The Radiation Of Spoof Surface Plasmon Polaritons

With the development of science and technology,electronic countermeasures capabilities have become more and more important in the game of great powers,and become an important manifestation of a country's comprehensive national defense capabilities.With the increasingly complex electromagnetic environment,microwave devices must be able to effectively resist electromagnetic interference and information interception.Spoof surface plasmon polaritons(SSPPs)are supported on artificially designed periodic structures in the microwave frequency band so as to achieve surface plasmon polariton(SPP)like properties that originally existed only in the optical band.They can thereby achieve a high degree of field enhancement and field confinement characteristics,which can effectively resist external electromagnetic interference.Electronic countermeasures have important application potential.At the same time,the SSPPs also have the characteristics of conformal transmission and low profile,which further expands their application range.In recent years,novel transmission lines and devices such as filters and power dividers based on SSPPs have been proposed,and their great potential in antenna design has also been developed.This thesis mainly focuses on the radiation of SSPPs.Based on the radiation regulation,we combine the periodic modulation theory with SSPPs,and design periodic radiation units to excite high-order harmonics on the transmission line of SSPPs so as to effectively transform highly constrained surface waves into free space waves.The radiation frequency and scanning angle are dynamically reconfigurable by loading varactor diodes,which provides effective solutions to the problems of dynamic radiation control,interference avoidance and signal interception.The main research contents and contributions are summarized as follows:1.First,the related theories of SSPPs is discussed.Focusing on the influence factors of the dispersion characteristics of SSPPs,the radiation mechanism of different types of SSPP antennas are researched.The Floquet theorem and the high-order harmonic excitation method are also studied,founding the foundation for subsequent design.2.A passive SSPP leaky wave antenna is proposed and realized.Firstly,the propagation properties and field distribution characteristics of SSPPs are studies.Secondly,combined with Floquet's theorem and the higher harmonic radiation theory,the SSPP transmission line is designed as the feeding structure of the antenna array.At the same time,radation units with small size are presented and high-efficiency feeding method is investigated so as to realize frequency-dependent beam scanning.3.An active SSPP transmission line is designed.Based on the property that the dispersion curve of SSPP structures changes with the capacitance of embedded varactors,an effective scheme is proposed to realize reconfiguration passband of the SSPP transmission line.By loading a varactor diode between the feed and the slot of the groove unit structure,the dispersion curve can be reconstructed,and the electromagnetic wave can be controlled to propagate in different frequency bands,which lays the foundation for the subsequent reconfigurable antenna design.4.A reconfigurable leaky wave antenna is designed and realized.A reconfigurable SSPP structure that can effectively excite the radiating units is proposed.The transmission pass band is adjusted by loading varactor diode on one side of the structure,and the radiating units are loaded on the other side.The efficient conversion from surface waves to free space waves provides a new solution for broadband and reconfigurable leaky wave antennas.