| Graphene is a two-dimensional material composed of a single layer of carbon atoms arranged in the same plane as a honeycomb.Once discovered,it has attracted the attention of many domestic and foreign scholars due to its unique microstructure and excellent dielectric properties.In this paper,combined with graphene material,a microstrip antenna that can generate orbital angular momentum vortex waves and a terahertz absorber with dynamically adjustable bandwidth were designed.The main research contents of this paper are as follows:（1）The structure and characteristics of graphene materials and the simulation software used in this paper were expounded,and it is pointed out that we can make graphene show various and unique physical properties by chemical doping,changing the number of layers,applying voltage and twisting,etc;The electrical conductivity,dielectric constant and refractive index of graphene were derived;The extinction cross section of trilayer graphene with Zn O substrate was simulated,which verified the correctness of the derived graphene electromagnetic parameters.（2）The modal number of orbital angular momentum can be used as a degree of freedom to modulate information,which provides a solution for improving spectrum utilization and system capacity.In view of the shortcomings of the existing orbital angular momentum antennas at home and abroad,such as:complex structure,high processing accuracy requirements,and complicated operations to change the modal number,etc.this paper combined graphene materials,and designed a microstrip antenna generating orbital angular momentum vortex waves.The simulation results show that when the chemical potential of graphene is 0.9e V,the S11 of the microstrip antenna can reach-47d B and the gain can reach 9.25d B at 14.9GHz.The antenna is light in weight,simple in structure,easy to process,and can generate stable orbital angular momentum vortex waves with modal numbers l=-2,0 and+2 only by adjusting the feed phase difference,which is expected to be used to improve spectrum utilization.and system capacity.（3）At present,the absorbers at home and abroad still have some shortcomings such as too narrow bandwidth,inability to dynamically control,and sensitivity to polarization angle,etc.To overcome the above shortcomings,this paper used graphene double rings to designed a terahertz absorber with dynamically adjustable bandwidth.Simulation results show that the absorber can achieve dynamic switching between broadband absorption mode and dual-frequency absorption mode.When the chemical potential of graphene is 0.5e V,the absorber works as a broadband absorption mode,which can achieve more than 90%absorption rate in the frequency range of 0.98-1.51THz,after adjusting the chemical potential to 0.7e V,the absorber switches to the dual-frequency absorption mode.At this time,the absorption rate of the absorber at 1.35THz is 98.65%,and the absorption rate at 1.75THz reaches 99.60%,which is almost perfect absorption.In addition,the absorber is simple in structure,still has broadband absorption characteristics within a certain incident angle range（0-45°）,and is also insensitive to polarization angle,and is expected to be used in electromagnetic protection,aircraft stealth and photoelectric detection.and many other fields. |
