Dispersion Control Of A Novel Surface Plasmon Waveguide And Its Engineering Application

Spoof surface plasmon polaritons(SSPPs)is a special electromagnetic wave mode excited on the surface of a specific periodic structure in the lower frequency band such as microwave or terahertz wave.This mode has the characteristics of high binding capacity,short working wavelength,low loss,wide bandwidth and convenient conformal transmission,so it has attracted extensive attention of scholars.With the gradual deepening of the research on the spoof surface plasmon,a series of new transmission lines and functional devices based on the spoof surface plasmon design have been designed and invented.This paper studies the functional devices of spoof surface plasmon transmission lines and their combination with traditional circuits,analyzes their propagation characteristics and phenomena,and designs SSPPs transmission devices.The main contents and contributions are summarized as follows:(1)A new dual passband filter structure with composite groove structure is designed.Firstly,the dispersion characteristics of the unit structure are calculated,and its microwave network parameters and equivalent circuit structure are deeply studied.It is shown that the structure can support a surface wave mode similar to surface plasmon polaritons(SPPs).Based on this,a composite groove waveguide structure is proposed.The upper layer is a curved metal strip loaded with curved corrugated lines and connected to the bottom metal layer through metal perforations.In the middle is a Rogers RT5880 dielectric plate,and the bottom is covered with a metal copper layer.Through detailed structural design and principle analysis,the mechanism of the dual passband filter of the composite groove structure is deeply studied,and the physical samples of the structure are manufactured.The results show that,the measured and simulated results are in good agreement.The S-parameters show that the SSPPs waveguide structure has high-efficiency transmission and low reflection loss in the designed 2.7 ～ 6.7 GHz and 7.7 ～ 9.1 GHz dual band passbands.The passband insertion loss is not less than-3 d B,the passband reflection is less than-10 d B,and the isolation band rejection is less than-15 d B.Most importantly,the band of waveguide structure can be controlled independently by the passband bandwidth of one band without affecting the other,which will provide great flexibility for the performance of the filter.In addition,the waveguide adopts a composite groove structure,which greatly reduces the size of the waveguide and realizes the miniaturization of the device.(2)Based on the theory of spoof surface plasmon polaritons,a dynamic controllable power divider based on a loaded varactor diode and an artificial surface plasma structure is designed.The structure is mainly composed of three parts: the first part is coplanar waveguide(CPW),which is mainly used to feed and receive electromagnetic fields.The second part is the transition from coplanar waveguide to spoof surface plasmon polaritons wave,which is mainly composed of metal flared ground and gradient groove to realize impedance and momentum matching.The third part is the waveguide part supporting SSPPs wave propagation,which is composed of a double-sided metal strip coupled with two curved single-sided metal strips,and a varactor is loaded in the coupling gap.By changing the capacitance value of the varactor,the frequency of the passband can be flexibly adjusted.The simulation and test results show that the new SSPPs unequal power divider can adjust and control the power distribution ratio in real time in the 5.5 ～ 6 GHz frequency band,and it has good frequency selectivity,especially the real-time response to varactor voltage,which can realize dynamic control and multi-function.(3)A sensor based on spoof surface plasmon polaritons structure,which can be applied in engineering and real-time monitoring of structural deformation,is studied and designed.The sensor adopts spoof surface plasmon polaritons structure,which is composed of periodic rectangular grooves and bent rectangular metal strips on the dielectric substrate.When the sensor is in use,it can transmit and receive wireless signals through a small unmanned aerial vehicle equipped with a microwave antenna.By detecting the drift of the frequency point of the reflected signal of the sensor,the looseness or deformation of the structure can be inferred.The sensor has the advantages of small size,real-time performance,strong anti-interference ability,highly integrated and high detection sensitivity.It has a good effect of detecting the structural deformation of glass curtain wall.When the structure is deformed or loose 1μm,and the detection distance between the antenna and the sensor is 25 mm,the sensor sensitivity is 177.33 kHz/μm,and the figure-of-merit(FOM)of the sensor is 126.