Research Of Resonant Antenna Based On Spoof Surface Plasmon Polaritons

Spoof Surface Plasmon Polaritons(SSPPs)are electromagnetic waves propagating along the interface between a metal and a dielectric.SSPPs waveguides exhibit unique characteristics,such as strong field confinement(large effective refractive index),low loss,low profile(surface wave)and so forth.Therefore,SSPPs waveguides have been widely used recently in Microwave and Terahertz devices,such as sensors,filters,and antennas,to name a few.From the antenna perspective,they are mainly employed as leaky-wave antennas,end-fire antennas or antenna feed lines,but few applications to resonant antennas have been found until now.Due to its merits of small size,the ease of achieving impedance matching and meeting the frequency band requirements,the resonant antenna is a type of widely-used antenna.This thesis highlights the study of SSPPs-based resonant antennas and consists of the main content as follows.1.The design principle of SSPPs-based resonant antennas is studied theoretically.From the Floquet theorem,the resonant condition of SSPPs resonant antennas is derived and calculated for a specific example.2.Dispersion characteristics of the SSPPs-waveguide unit structure and modal excitation properties of SSPPs resonant cavity are analyzed.Based on the SSPPs resonant-antenna design principle,a dual-band SSPPs resonant antenna utilizing the even modes of the SSPPs waveguide is proposed and designed.The antenna comprises two parts,namely an SSPPs cavity printed on the substrate top face and a monopole antenna aligned parallel to the cavity axis and fed by a coplanar waveguide(CPW)printed on the substrate bottom face.The monopole antenna excites the firstand second-order even modes of the SSPPs cavity through coupling,which leads to the dual-band operation of the antenna.The dual-band antenna measured with 14.5mm × 7 mm × 0.508 mm attains gains of 3.12 d Bi and 3.3 d Bi along with total efficiencies of 96.2% and 95.2%,respectively,at the two resonant frequencies of 6.3GHz and 13.6 GHz.The antenna has the characteristics of simple structure,small size,well-defined omnidirectional radiation pattern and high total efficiency.3.A dual-band SSPPs resonant antenna utilizing the even and odd modes of the SSPPs waveguide is proposed and designed.The antenna comprises an SSPPs resonant cavity,an L-shaped monopole antenna fed by a CPW and a reflective metal printed on the side wall of the dielectric substrate.The L-shaped monopole antenna excites the first-order even and odd modes of the SSPPs cavity through coupling,which leads to the dual-band operation of the antenna.The dual-band antenna measured with 15 mm × 14 mm × 0.508 mm was fabricated and measured.The measured results agree well with the simulation results.Measured results show two resonant frequencies at 14.7 GHz and 17.4 GHz with a frequency ratio of 1.183.The measured gains are 7.06 d Bi and 5.67 d Bi at the two resonant frequencies,respectively,while both of the total efficiencies exceed 90%.The antenna has the characteristics of small size,high gain and high efficiency.Furthermore,the operating band and frequency ratio of the dual-band antenna can be independently and flexibly adjusted in response to the practical requirements.4.A broadband SSPPs resonant antenna is proposed and designed.The antenna is built from an SSPPs waveguide with a symmetrical H-shaped unit structure,and fed by a coaxial probe.Utilizing the dispersion characteristics of the even and odd modes of the SSPPs waveguide,the antenna operating bandwidth is predominantly broadened.Its operating band is 8.8 GHz～12.4 GHz with a relative bandwidth of33.9%.Across the operating band,the radiation efficiency is greater than 92% and the maximum gain attains 6.8 d Bi.The antenna features low profile,small size,and simple structure,facilitating its integration into various wireless and sensing systems.Moreover,the variation of the operating band can be easily realized in the antenna design.