Research On Characteristics Of Frequency Selective Surface And Its Applications In Antenna

In recent years,the rapid development of wireless communication technology has brought us many conveniences,and modem life is increasingly relying on wireless communication.Faced with limited spectrum resources,single frequency communication devices are hard to meet the severe communication requirements.Dual-frequency and multi-frequency communication has become a research hotspot.As a kind of spatial filter,frequency selective surface(FSS)can realize full reflection or full transmission of some electromagnetic waves at certain frequency and change the transmission characteristics of electromagnetic wave,so it has become an important part of multi-frequency communication system.It is widely used in both military and civil fields.In this thesis,the design of multi-band FSS and its application to radar cross section(RCS)reduction of microstrip antenna are studied emphatically.The main works and innovations are as follows.(1)The background,significance,research history and current situation of FSS are briefly introduced.The filtering principle of the patch type and the aperture type FSSs is analyzed.The basic idea of mode matching and spectral domain method for solving FSS is derived based on the Floquet theorem.The main parameters that affect the transmission characteristics of FSS and the generation and suppression of gate lobes are analyzed.(2)A novel X/Ku band FSS is proposed based on the analysis of traditional complementary structure.The proposed FSS consists of two-layer dielectric board loaded with three-layer metal patch instead of loading the complementary metal patch on both sides of the single layer dielectric board.The transmission characteristics,polarization stability and angle stability of the designed FSS are analyzed by HFSS software.The influence of relative permittivity and dielectric thickness on the transmission coefficient of FSS is studied.Simulation results show that the designed FSS has the broadband characteristics,its passband is quiet flat and smooth,in which the insertion loss is low,and it is not sensitive to electromagnetic waves with different angle of incidence and polarization.(3)A quad-band FSS is designed based on different size resonant units.A stopband and three passbands are obtained through the combination of the square ring patch and the regular octagon ring with different sizes and the regular octagon patches.The stopband is located at the X band,and the three passbands are located at Ku-,K-and Ka-bands respectively.The simulation results show that the designed FSS has good angle stability and polarization stability.(4)The designed dual-band FSS is loaded on the microstrip antenna as the radome,the gain and the RCS of the microstrip antenna with and without loading FSS are analyzed.After loading FSS,the directivity of the antenna is improved,the maximum gain is increased by 4.9dB,and the RCS in the range of 7?11 GHz is reduced to a maximum of 13.67dB.Thus,it is proved that the designed dual-band FSS can raise the antenna gain without affecting the reflectivity of the antenna and reduce the RCS of antenna.