Research On Transmission Control Based On Spoof Surface Plasmon Polaritons

Spoof Surface Plasmon Polariton(SSPP)is an electromagnetic wave that transmits along the surface of a periodic metal structure.It is similar to Surface Plasmon Polariton(SPP),it decays exponentially in the direction perpendicular to the metal surface,and its transmission mode is surface wave and has slow-wave characteristics.Since the plasmon resonance frequency in metal is much higher than the microwave terahertz frequency band,the metal behaves as a perfect electronic conductor instead of plasma in this frequency band.The current SSPP transmission structure is a periodic metal slit and slot structure in subwavelength so-called spoof surface plasmons.The transmission characteristics are also affected by the transmissive structural parameters,so it has significant research value and application prospects.This paper studies the transmission control devices based on artificial surface plasmons.The main contents and achievements of the dissertation are as follows:First and foremost,the dispersion characteristics of an asymmetrical SSPP transmission structure are studied,and it comes to the fact that the depth of the grooves etched on the metal layer is the main factor affecting the transmission characteristics.According to the designed working frequency band,the size of the transmission structure is determined.Through simulation calculation,it is obtained that the insertion loss from the S21 parameter is always greater than-2dB,and the return loss S11 parameter is less than-15 dB in the range of 5GHz to 13.3GHz,which indicates that the transmission line possessed good transmission capacity for surface waves.Secondly,the dynamic control characteristics of stopband filtering on SSPP transmission lines are studied.By adding resonant units to the grooves of the SSPP transmission structure,the dispersion characteristics and guided wave field distribution of the SSPP transmission line are changed to realize the stopband filtering function.Furthermore,by adding vanadium dioxide material with phase change characteristics to the resonant unit,the simulation reveals that the center frequency of the stopband filter dynamically changes within a 1.5 GHz bandwidth.The SSPP transmission line and the SSPP transmission line with stopband filtering and modulation capabilities are processed.The experimental results show that the upper cut-off frequency of the SSPP transmission line is 13.24 GHz,which is fairly consistent with the simulation results.Specifically,when the resonant unit is open,the filtering stopband is centered at 8.5 GHz within a 0.42 GHz bandwidth;when the resonant structure is short-circuited,the filtering stopband characteristics disappear.Finally,the leakage characteristics of surface waves in the SSPP transmission line are studied.According to the theory of surface impedance sinusoidal periodic modulation,a simplified design process of SSPP modulation structure for surface wave radiation is proposed.A leakage-wave periodic structure with a radiation frequency of 8 GHz,a radiation angle of 26.5 degrees,and a gain of 11 dB is designed.The deviation of the radiation angle between theoretical and simulated results is less than 0.1 degree.Under the condition of ensuring radiation efficiency and radiation directivity,the sweeping frequency angle in the 1.2 GHz range from 7 GHz to 8.2 GHz is 13.5 degrees.It indicates that the surface impedance sinusoidal periodic modulation leaky-wave antenna based on SSPP transmission line has good directivity and frequency scanning characteristics.