Research On Microwave Filters Based On Spoof Surface Plasmon Polaritons

Surface Plasmon Polaritons are electromagnetic waves propagating along the interface of metal and dielectric at optical frequencies,which have the characteristics of subwavelength confinement,near field enhancement and slow wave.In 2004,J.B.Pendry et al.proposed the concept of Spoof SPPs,and then Hibbins et al.verified the existence of Spoof SPPs in microwave regimes,attracting wide attention and research of scientists all over the world.This paper studies several microwave filters based on Spoof SPPs,the main research content is as follows:1.A low-pass filter based on Spoof SPPs is proposed.The inner conductor of coaxial waveguide is etched with periodic grooves to support Spoof SPPs and the outer conductor,a hollow cylinder,is utilized to ensure the efficient signal transmission.The filter realizes momentum matching by using a gradient structure,and high restraint outside the band and low insertion loss inside the band are realized.2.A bent structure has been investigated to realize the miniaturization of the filter.The ground of CPW is etched with periodical grooves to realize a low-pass filter.There is a negative correlation between the depth of the groove and cut-off frequency.To miniaturize the device,a T-shaped equivalent groove is introduced to control the frequency.3.A wideband band-stop filter based on Spoof SPPs is proposed.A T-shaped periodical strip is placed at the back of CPW,and the T-shaped design is used to reduce the physical dimension.By introducing a defect on the strip a very narrow stop-band in the working band is achieved.The frequency and suppression intensity of the narrow stop-band have a good controllability.By using the cascade of nine defects a wideband band-stop filter with high restraint and low insertion loss is realized.4.A band-pass filter based on Spoof SPPs is proposed.A microwave line with grids and matching structure on one side is designed as a low-pass filter.On the other side,periodical split-ring resonators are placed to filter out a certain low frequency band forming a band-pass filter.