Study On The Filter And Sensor Based On Spoof Surface Plasmon Polaritons

Spoof surface plasmon polaritons（SSPPs）are special surface waves that can propagate along special sub wavelength periodic structures in low frequency electromagnetic bands such as terahertz and microwave.Spoof surface plasmon polaritons have received great attention in recent years due to their high sub wavelength binding,strong dispersion,and local field enhancement properties.As the research in this field continues to deepen,more and more SSPPs functional devices have been proposed and have broad application prospects.Surface plasmons are divided into two types:transmissive surface plasmons（SPPs）and non-transmissive localized surface plasmons（LSPs）.In this thesis,according to their different characteristics,an ultra-wideband terahertz bandpass filter based on SSPPs and a sensor with high sensitivity and high quality-factor（Q-factor）based on spoof LSPs are designed,respectively.The main research contents are as follows:1.A terahertz ultra-wideband bandpass filter based on SSPPs is studied and designed.The low-pass characteristics of the bandpass filter are achieved through the high-frequency cutoff characteristics of SSPPs,while the high-pass characteristics are achieved through an interdigital structure added to the middle of a spoof surface plasmon polariton element.The designed filter has a compact structure and small size with 1.56λ₀×0.6λ₀ and has the following advantages:（1）High transmission efficiency:|S₁₁|is lower than-10d B in the operating frequency range of 0.65THz-2.1THz.（2）Strong out of band suppression performance:|S₂₁|is lower than-15d B in the range of2.18 THz to 2.5 THz.（3）It has ultra-wideband performance with a relative bandwidth greater than 102%.A microwave frequency band filter sample was processed and measured to further verify the correctness of the filter structure design.The measured results are consistent well with the simulation ones,indicating that the filter has practical application value.2.A microwave sensor with high sensitivity and high Q-factor based on spoof LSPs was studied and designed.The designed sensor is composed of three independent spoof LSPs structures and are regarded as the outer,the middle and inner ring.Through the coupling of three spoof LSPs resonators,the higher-order modes of the sensor are excited and the quality factor of the sensor is improved through the hybrid spoof LSPs.The simulated and calculated results show that in the operating frequency band of 1-7GHz,the maximum sensitivity of the sensor is up to 1.47 GHz·RIU^-1,and the maximum Q-factor is 414.Compared with the single and dual-layer spoof LSPs resonators,the sensitivity is increased by 4.9 times and 2.1 times,respectively,and the Q-factor is increased by 5.2 times and 2.5 times,respectively.A microwave sensor sample was processed and measured,the measured results are basically consistent well with the simulation ones,further verifying the correctness of the sensor structure design.