| With the fast development of detection technology,the stealth needs of antennas are getting stronger.In addition to the shape stealth design,most of current antenna stealth measures belong to static stealth or out-of-band stealth.The common camouflage screens are mainly used to meet the static stealth requirements of antennas.However,the camouflage screens must be withdrawn when the antenna is working.Frequency selection surface radomes are used for stealth in antenna working state,only able to solve out-of-band stealth problems.Applying electromagnetic bandgap structures(EBG)can partially realize in-band stealth of the antenna.However,the application of EBG is limited to flat antennas,and can only solve narrowband backscattering reduction at normal incidence.The emergence of meta-materials provides a way to achieve broad-in-band stealth of antennas.Compared to the above antenna stealth technologies,stealth technology based on meta-surface materials can achieve wide-band stealth of the antenna reflection surface by adjusting the sub-wavelength size of the meta-surface cells,from the brand new mechanism of electromagnetic phase regulation.In this thesis,based on reflective meta-surfaces,the RCS of the antenna is significantly reduced in wide band through adjusting the phase values of the reflected electromagnetic waves.Meanwhile,by using meta-surfaces,the calibration of wavefronts is achieved,and the performance of directivity and gain is also enhanced with the RCS effectively reduced simultaneously.In this thesis,the electromagnetic phase regulation mechanism based on the generalized Snell's law is studied in detail,and based on which,high directive and low scattered single-feed single-beam dihedral corner-reflector antenna,single-feed single-beam trihedral corner-reflector antenna,half-space multi-feed multi-beam trihedral corner-reflector antenna,full-space multi-feed multi-beam trihedral corner-reflector antenna,and single-feed multi-beam trihedral corner-reflector antenna are respectively designed.This thesis analyzes in detail from aspects of principle design,simulation and experimental verification.The validity of the theoretical design is verified by the results comparison,which enables the antenna to achieve high directivity and low scattering with its performance effectively enhanced.The main research contents of this thesis are as follows:(1)Starting from the generalized Snell's law,general formulas for the phase compensation of one-dimensional and two-dimensional planes covered by meta-surfaces are derived.Taking a typical reflective meta-surface cell as an example,the basic principle of phase regulation is studied,and the general method of electromagnetic parameter retrieval of meta-surface is summarized.(2)The radiation and scattering characteristics of a typical corner-reflector antenna is analyzed.Based on gradient corrugation structures,a dihedral corner-reflector antenna with high gain and low scattering is designed.Compared with a traditional dihedral corner-reflector antenna,the gain is effectively increased and the broadband backward RCS reduction is achieved.(3)Based on a typical structure of reflective meta-surface,a dihedral corner-reflector antenna with high directivity and low scattering is designed,on basis of which the deflection of the outgoing beam is achieved.Then a trihedral corner-reflector antenna with high directivity and low scattering is further designed,and design cases based on different angles of reflection panels are given.Through loading meta-surfaces,the antennas above all achieve a high directivity,and the scattering characteristics of the antenna panels are significantly reduced over a wide frequency range.(4)Based on a typical structure of reflective meta-surface,a highly directive and low scattered half-space multi-beam trihedral corner-reflector antenna under three,four,five and six feed sources are designed respectively.And on basis of this,a full-space six-beam trihedral corner-reflector antenna with high directivity and low scattering is further designed.What is more,all the antennas above are simple in structure and easy to fabricate,holding a significant characteristic of broadband RCS reduction simultaneously.(5)The generation principle of multiple beams based on a single feed is analyzed.And based on a typical structure of reflective meta-surface,a three-beam trihedral corner-reflector antenna based on a single feed with high directivity and low scattering is designed.Through loading meta-surfaces,a three-beam directional radiation under a single-feed source is realized with a significant broadband backward RCS reduction. |
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