Antenna Analysis And Stealth Technology Research Based On Electromagnetic Metasurface

In the field of military operations,the development trend of broadband and ultra wideband radar has put forward increasing requirements for broadband RCS reduction performance of the stealth antenna.In the field of wireless communication,in order to increase the channel capacity,the needs of the communication system for broadband antennas are becoming stronger.In this background,metamaterial and metasurface have attracted attention due to the extraordinary electromagnetic characteristics and broadband application potential.Based on the important role of metasurface on antenna broadband stealth and high-efficiency radiation,different types of high-performance electromagnetic metasurface are analyzed and studied in this dissertation.At the same time,the radiation and RCS performances of the integrated structure of antenna and metasurface have been analyzed,and the broadband RCS reduction and broadband radiation effects of various antennas and arrays have been realized.In terms of broadband stealth of the antenna and array,two types of radar cross section（RCS）reduction methods of passive cancellation and electromagnetic absorbing are mainly used in this dissertation.Firstly,with the help of passive cancellation principle,two types of array antennas with high-efficiency radiation and wide in-band and out-of-band RCS reduction performances are designed.For microstrip arrays based on shape technology,the RCS reduction at the normal incidence of plane wave is achieved by introducing grooves with special structures on the patch and ground of the antenna element to change the current path and obtain the effective reflection phase difference.By parametrically designing the shape of the radiation patch,RCS reduction at the grazing incidence of large angle is realized.Finally,the array achieves broadband and significant reduction of RCS in both incident cases while the gain almost maintains unchanged.For antenna arrays based on metasurface,by using double-layer miniaturized bandpass FSS and single-layer broadband AMC structure,a novel AMC-FSS radome with broadband and efficient transmission characteristics and ultra wideband RCS reduction potential is designed.When the radome is loaded,the array has a wide 1d B gain loss bandwidth and it achieves ultra wideband RCS reduction including three bands of C,X and Ku.Secondly,with the help of electromagnetic absorption principle,a multi-resonant metamaterial absorber unit cell with ultra wideband absorption ability is designed and an equivalent circuit model is established to analyze its working mechanism from the perspective of circuit.Combined with the broadband FSS structure,a radome which can realize low-frequency ultra wideband absorption and high-frequency efficient transmission is proposed.In addition,the radome is integrated with the designed high-performance satellite communication antenna array and the ultra wideband reduction of monostatic and bistatic station RCS of the integrated array is achieved.In terms of the design of broadband metasurface antennas,this dissertation focuses on the bandwidth expansion method of metasurface antennas.By the broadband design of radiation structure and the introduction of broadband matching structure at the key position of the feeding slot,two broadband metasurface antennas based on microstrip line aperture coupled feeding and coplanar waveguide aperture coupled feeding are designed.For the first antenna,a novel metasurface unit cell with multi-resonance characteristics（different resonant frequencie at different polarization incidence）is firstly proposed,the unit cell and its 90-degree rotation unit cell are specifically arranged to form an aperiodic radiation patch array.Secondly,a sector-matched structure and a non-equal-width strip slot are introduced at the ends of the microstrip feeding line and coupling aperture respectively.Under the dual action of broadband radiation structure and feeding structure,the impedance bandwidth of the metasurface antenna reaches 35.6%.For the second antenna,the high-order mode radiation is excited by the size control and reasonable array arrangement of the metasurface multi-patch at first,which effectively expands the bandwidth of the antenna at the low frequency.Secondly,by introducing rectangular step-like matching groove and step-like matching branch at the end and start of the feeding slot respectively,the impedance bandwidth at the high frequency is significantly increased,and finally the-10d B impedance bandwidth of 67.7%is obtained.In addition,a metasurface unit cell with broadband polarization rotation function is proposed,and a high-performance circularly polarized metasurface antenna is obtained by the finite periodical arrangement of the unit cell and the combination with an effective feeding structure.Also,the unit cell can be alternately arranged with its mirror unit cell to form a polarization-rotation metasurface,which can achieve a wideband reduction of monostatic RCS by the principle of passive cancellation.In terms of grating lobe suppression of large-spacing antenna arrays,considering the large size of the metasurface antenna proposed in this dissertation（greater than 1λ₀,even reaching 1.5λ₀）,when the antennas are uniformly arranged to form a linear array or planar array for beam scanning,the grating lobe appears in the visible area.Therefore,an improved iterative fast Fourier transform method based on the idea of large-spacing sparseness is utilized in this dissertation to achieve the array synthesization of large spacing and no grating lobes.Firstly,the simulation results of large-spacing metasurface linear array are given,and then the basic principle of IFFT method and the process of large-spacing sparse synthesis are introduced.Finally,several specific comprehensive examples are used to show the scanning characteristics of large-angle and no grating lobe of the linear array and planar array,and the sparse array meets the comprehensive requirement of minimum array spacing of ultra-large spacing.