| New artificial electromagnetic materials are attracting more and more scholars' attention due to their unique electromagnetic properties.In accordance with the direction of propagation of electromagnetic waves to points,it can be divided into reflection-and transmission-type materials.In practical applications,reflective electromagnetic materials often have interference between reflected waves and incident waves,so in this thesis,we will mainly study the transmission of artificial electromagnetic materials and their applications in the field of microwaves.The main research contents are as follows: a broadband frequency selective rasorber(FSR),a Frequency Selective Surface(FSS)coating to improve antenna's gain and a broadband lens based on the phase gradient metasurface.In the first part of this thesis,we mainly study a low wind resistance FSR based on the "pinwheel" shaped coupling pole array.First of all,the design principle of FSR is studied,and an equivalent circuit model of FSR is constructed in ADS simulation software.The FSR structure is mainly composed of lossless layer,medium matching layer and lossy layer.Among them,the lossless layer is frequency selective surface,the medium matching layer is an air layer and the lossy layer is a lossless layer loaded with lumped components.In order to reduce the insertion loss of the transmission window and wind resistance of the FSR,the FSR is hollowed out.Simulation and experimental results show that the FSR insertion loss at the frequency of 7.71 GHz is1.016 dB,and the strong reflection on both sides of the passband is reduced to less than-10 dB.The advantages are: this structure has a low insertion loss within passband and meanwhile the strong reflection on both sides of the passband are reduced.Besides,hollow processing can effectively reduce the wind resistance and the insertion loss of the structure.The second part of this thesis focuses on a FSS cladding,and it is used to improve antenna gain.Firstly,the principle of using FSS to increase antenna gain is analyzed.Secondly,a FSS cladding is designed consisting of a square ring of metal and an FR-4 dielectric substrate.The FSS cladding is placed above the microstrip slotted source antenna,transmitted electric field constructively interferes with the electric field reflected by the FSS cladding,which changes the entire antenna from the original omnidirectional radiation to directional radiation and meanwhile increases the average gain by 98.7% in the band of 7.2 ~ 8 GHz.The third part of this thesis mainly studies a transmission wideband lens used in X-band.FSS cladding design in the second part has a limitation,the source antenna requires a full ground,so a lens based on the phase gradient metasurface(PGMS)in designed in the chapter,which can effectively increase the antenna gain and meanwhile the antenna types are unrestricted.The lens consists of a metal square patch and a thin square ring around the metal square patch.By adjusting the side length of the square patch to achieve the transmission curve phase 0 ° ~ 360 ° phase compensation.The simulation results show that the lens can realize a focusing propertie for electromagnetic wave in the frequency band of 8.2 ~ 10 GHz.Finally,the physical processing and testing were performed.The lens was loaded onto three patch antennas operating at 8.2GHz,9.1GHz and 10 GHz respectively.The test results show that the gain of the three antennas are significantly increased after the broadband lens is loaded. |
PDF Full Text Request