Study On Artificial Control Of Dual Band Electromagnetic Wave Based On Frequency Selective Surface

Frequency selection surface is a planar structure composed of many same or similar elements arranged on the dielectric layer periodically.It can control the amplitude and phase of electromagnetic wave through different size parameters,so as to realize the control of electromagnetic beam.Because of its small size and light weight,it is widely used in the fields of beam convergence,electromagnetic stealth and beam shaping.Since the beginning of the new century,especially in the past ten years,the research and development of wireless communication technology has become faster and faster,the communication mode of only a single frequency band is far from meeting people's demands.Dual-frequency and multi-frequency communication has gradually become a hot research direction.Frequency selective surface structure can artificially introduce a sudden phase to electromagnetic wave,so as to realize the artificial control of electromagnetic beam as desired,but the research on them is still focused on a single frequency band.Therefore,based on the frequency selection surface working in the double pass band,this paper studies the regulation of electromagnetic waves.Firstly,three kinds of structures of dual band frequency selective surfaces working below 20 GHz are designed.Their corresponding equivalent circuit models are analyzed respectively in detail,and the transmission curves of the circuit simulation results and the actual structure are fitted.Then,based on the second order structure,the effects of different physical parameters on the transmission characteristics are analyzed.For the second structure,the electromagnetic wave can be freely regulated to a certain extent;for the third structure,the two frequency bands can be completely freely regulated.It is verified that the element structure designed can show stability for various incident angles and polarization modes of electromagnetic wave.By designing the third-order element structure,the 360° phase coverage requirement is realized.Then,the beam deflection surface is designed based on the proposed second and third structures.Based on the second and third structure design of the deflection of the surface of the beam deflection in different angles,the two frequencies corresponding to the wavelength is different,so you can through the two frequency band design to achieve the same phase gradient different deflection Angle of the beam,the structure of the second and the third kind of structure distribution of 90 ° and 30 ° of the surface of the unit to build a beam deflection,the second kind of structure to achieve the 69 ° 18 ° deflection,and the third kind of structure to achieve the 48 ° and 14 ° deflection of the beam;Based on the third structure,the beam deflection surface with two frequency bands at the same Angle is designed,and the beam deflection surface from 14° to 63° is simulated,which shows that the beam deflection surface can achieve any Angle deflection,and the correctness of the structure is verified.Then,the beam deflection lens is designed based on the proposed second and third structures.Structure design based on the second and third deflection beam deflection lens in different angles,the two frequencies corresponding to the wavelength is different,so you can through the two frequency band design to achieve the same phase gradient different deflection Angle of the beam,the structure of the second and the third kind of structure distribution of 90 ° and 30 ° deflection of the beam unit to construct the lens,the second kind of structure to achieve the 69 ° 18 ° deflection,and the third kind of structure to achieve the 48 ° and 14 ° deflection of the beam;Based on the third structure,the beam deflection lens of two frequency bands with the same Angle is designed,and the beam deflection lens from 14° to 63° is simulated,which shows that the beam deflection surface can achieve any Angle deflection,the accuracy of the structure is verified.Finally,based on the third structure,the beam focusing surface is designed.Focusing surfaces focusing on different focal points(f1 =180mm,f2 =300mm)and focusing on the same focal point(f1 =f2=180mm)are designed respectively.The simulation results are in good agreement with theoretical values to achieve sub-wavelength focusing.In addition,a focusing/deflecting surface is simulated,with the first band focusing at 150 mm and the second band beam deflecting at 30°.A longitudinal bifocal lens is designed to realize the focus of two foci,but the focus is shifted due to the mutual influence of the phases of the two foci.