Research On The Bi-functional Holographic Antennas Based On Meta-surfaces

In recent years,artificial electromagnetic metamaterials have the characteristics of flexible adjustment of reflection phase through resonance with incident electromagnetic waves,and have the advantages of low loss,low cost,and easy processing,possessing wide application prospects in the field of electromagnetic communication.The holographic impedance modulation surface is a surface that uses the surface impedance of the meta-surface to perform impedance modulation.Applying the holographic theory in optics to the electromagnetic field,the surface current is controlled by adjusting the surface impedance of the meta-surface to perform the leakage wave radiation,which demonstrates the advantage of a low profile and easy beam control.This paper focuses on the regulation of the abnormal reflection phase and surface impedance of electromagnetic waves by meta-surfaces,and conducts beam analysis of electromagnetic waves with different radiation dimensions.The details are as follows: 1.The generalized Snell's law is introduced,and the corresponding artificial meta-surface structures are constructed accordingly.The Floquet model is utilized to simulate the artificial electromagnetic meta-surface element,and the phase response affected by the azimuth angle and the size parameters of the element structure is obtained.A highly directive reflecting antenna with the center frequency of 20 GHz is constructed.2.The holographic theory in optics is applied into the design of planar antennas electromagnetic field.The eigenmode simulation on artificial electromagnetic meta-surface elements is performed,and an impedance fitting curve that affects the size of the element structure is obtained.By sinusoidal modulation of the surface impedance of the meta-surface elements,a highly directive holographic impedance surface antenna with the center frequency of 15 GHz is constructed.3.The integrated design of frequency-selective surface and holographic impedance surface is proposed.Through the phase control and surface impedance information of the meta-surface unit of the same unit size,the relationship between the surface impedance of the meta-surface unit and the abnormal phase is analyzed and the feasibility of integrated design is proved.A bi-functional antenna that adapts to impedance modulation and anomalous reflection phase regulation respectively is proposed.After comparison,it is determined that the bi-functional antenna adapted to the adjustment of the abnormal reflection phase has a greater radiation performance.The unit of the surface is designed based on the holographic principle and the principle of periodic impedance modulation,and the abnormal reflection phase of the meta-surface is carried out based on the generalized Snell's law.The high-gain reflection at 20 GHz is achieved with the source feeding at the focal point of the antenna,and the function of directive radiation is satisfied at 15 GHz with the feeding source locating at the center of the antenna arrays.4.The methods of direct separation and field superposition for designing the dual-beam holographic impedance surface antenna and the flat reflector antenna are compared and analyzed,and the dual-beam integrated design of frequency selective surface and holographic impedance surface is established by the method of field superposition.The method of adapting to the regulation of abnormal reflection phase to design the dual-beam bi-functional antenna is utilized to achieve the performance of the high-gain dual-beam reflection at 20 GHz with the source feeding at the focal point of the antenna,and the functions of dual-beam and directive radiation are satisfied at 15 GHz with the feeding source locating at the center of the antenna arrays.