The Planar Design And Research Of Helical Structure Metamaterials

Metamaterial is a new type of artificial material.By embedding artificially geometric structure into the dielectric substrate,it can achieve effective regulation of electromagnetic waves.In the research of metamaterial,chiral metamaterial occupy an important position.As the most common chiral structure in nature,spiral structures have been widely used in circular polarizer and polarization converters.In 2009,JKGansel first used a metal single-arm spiral as a metamaterial unit,and found that the metal spiral structure has good wide-band circular dichroism in the optical band.Based on this,a circular polarizer was developed,which has attracted widespread attention..However,whether it is a circularly polarized antenna or a polarized converter,the spiral structure has the problems of large axial size,poor structural consistency,and difficulty in integration,and the preparation process of the multi-arms spiral is complicated,which is not conducive to processing.Therefore,it is of great significance to use a planar structure such as a PCB to carry out the planarization design of the spiral structure and realize the similar electromagnetic characteristics of the metal spiral.The main work studied in this paper is as follows:First,the metamaterial properties of spiral and planar spiral rings are studied.The metal spiral and Archimedes spiral structures working in the microwave region were designed,and the single-arm and multi-arms situations were simulated.The effects of axial dimensions and spiral turns on performance were discussed.The simulation results show that the single-arm and dual-arm metal spirals can achieve wide-band differential absorption of circularly polarized waves.The three-arm spiral structure does not have this characteristic,and the larger the axial size,the better the differential absorption characteristics.The use of a spiral antenna 's theory provides a theoretical explanation of this property.Unlike the properties of metal spirals,Archimedes spirals can achieve polarization-insensitive narrow-band absorption,and the more the number of spiral turns,the better the absorption effect.In addition,an S-parameter inversion method is derived to approximate the equivalent electromagnetic parameters of metamaterial.Then,in view of the large axial size of the traditional spiral,the design of a planar multi-layer spiral structure using metal strips and through holes on the PCB is proposed.The designed structure and metal spiral have similar symmetry.The planar multi-layer spiral structure is simulated,and the effects of parameters are discussed.Simulation results show that the planar dual-arm spiral structure can achieve differential absorption of circularly polarized waves,and the planar quad-arm spiral structure can achieve two-way polarization-insensitive absorption,but the operating frequency bands are narrow.From the perspective of the RLC resonance circuit,the electromagnetic characteristics of the designed structure are analyzed,and the equivalent electromagnetic parameters of the designed metamaterial are calculated using the S-parameter inversion method.Finally,the design of the helical antenna is performed using this multi-layer structure design.With reference to the theory of normal mode helical antennas,a planar dual-arm helical antenna working around 5GHz is designed,and the influence of parameters such as the radius of the arc is discussed.Simulation results show that the design can achieve good axial circularly polarized radiation.Compared with the traditional helical antenna,the size of the entire antenna structure is smaller,which facilitates integration and provides new ideas for the design of the helical antenna.