Research On Microwave Filters Based On Spoof Surface Plasmon Polaritions

Surface plasmon polaritons(SPPs)are essentially two-dimensional surface waves,which propagate on the interface between metal and dielectric in the optical frequency.Spoof Surface Plasmon Polaritions(Spoof SPPs)are a kind of surface electromagnetic wave which is confined by grooves or holes in the metal surface and propagating along the surface.The characteristic of Spoof SPPs is controlled by the geometrical parameters of the metal surface,which can be designed to control the microwave frequency of Spoof SPPs in microwave frequency.Based on the theoretical analysis and research of the dispersion characteristics of Spoof SPPs in the groove structure of metal surface periodic array,4 microwave filters have been designed based on spoof surface SPPs,and the main results are as follows:1.Based on Spoof SPPs low-pass filter is designed.The design of the device is engraved in the thin groove structure of periodic array on the surface of the metal,and combined with Mach-Zehnder interferometer(MZI)structure,analyzing its filtering characteristics.The angle of the two interference arms of MZI is 60°,when the electromagnetic wave from the input port through the splitter,the signal are divided two as 1:1,and propagating along the upper and lower interferometer arms respectively.When the two signal propagate through anther splitter at output port,they couple into one signal and out.Through the analysis of the S curve,the design of the low-pass filter of 3dB bandwidth from 2.1GHz to 10.7GHz,bandwidth with8.6GHz,the cut-off frequency of 15 GH,and the metal groove structure of the gradual frequency of the dispersion curve.2.The structure of MZI is improved,the length of one of the interference arms is changed,and the path is different when the signal is divided into two channels.Electromagnetic wave phase is different due to the different electromagnetic wave propagation path makes at the output of the combiner coupled when,after a phase of the MZI difference formula,theoretical calculation destructive interference of frequency,and it is proved by the simulation to the S curve,verified,in the pass band range two interference cancellation frequency: 8.65 GHz and 10.5 GHz.A novel low-pass filter is designed with two notch filters.3.Based on Spoof SPPs,band-pass filter is designed.Device is designed in the ultra-thin metal surface engraved with two opposite metal groove structure,so that the electromagnetic wave after the coupling part is divided into two up and down through the transmission of signals.Coupling part,using the method of microwave network analysis,which can be analysed as the four port network,according to the symmetry,simplified to two port network.Analysis of the coupling part of the pitch coupling and coupling unit number for band-pass filter pass band range of influence,through the simulation analysis of coupled to the spacing is 1mm and coupling unit number are 4,having widest bandwidth,from 4.8Ghz to 8.5Ghz,bandwidth with3.7GHz.Changing one of in the length of a transmission arm,bandpass filter based on the changes in the length of a transmission arm,the two signals in the output coupling part have phase difference,based on the phase difference formula,the frequency cancellation.After the simulation,further validation,the obtained filter can filter the 5.8GHz and 8.26 GHz,two frequencies.A band-pass filter was designed.