Radar Cross Section Reduction For Antennas Based On Periodical Electromagnetic Structures

With the development of electronic warfare,more and more attemtions have been paid to the stealthy technology,which requires a better performance of antennas.Since the stealthy characteristic of radar is mainly determined by the antenna performance,the radar cross section(RCS)reductions for antennas have get extensive attentions.However,the low RCS design for antenna is restricted by its radiation performance.Accordingly,how to reduce the RCS,as well as maintain the radiation performance of the antenna become an important research interest.Periodical electromagnetic structure(PES)can control the propogation of ecletromagnetic wave,which has already been applied in the RCS reduction(RCSR).Unfortunately,the recent design of PES is not easy conformal with antennas.Therefore,in this paper,the features of two kinds of PES,namely,radar absorbing material(RAM)and electromagnetic band gap(EBG)structure,are discussed.Furthermore,wideband and multiband RAMs are obtained based on the PES.In addition,in order to fulfill the recent stealthy requirement of antennas,we introduce the PES into the antenna design,to achieve the gain enhancement as well as RCSR of antennas.The research contents of our work are as follows:(1)The characteristic of EBG structure,as well as the impact of EBG pattern and dimension on the RCS performance of the checkerboard surface are studied.Our research shows that,compared with the central surrounded pattern,the adjacent pattern has a better RCSR performance.In addition,with the increase of the number of the unit cell in one period,a better RCSR performance is also observed.(2)The implementations for multiband and wideband RAMs are discussed.A polarization insensitive triple-band perfect metamaterial absorber is proposed based on the2^nd order circular fractal structure.In addition,two kinds of wideband wide angle RAMs are obtained by taking use of chip resistors and printed Tantalum Nitride material.(3)Based on the multiple reflection between the partially reflecting surface(PRS)and ground,as well as the absorption performance of the RAM,we present a high-gain PRS antenna with both in-band and out-of-band RCSR.The peak gain of the proposed antenna is18.4 d Bi.Compared with the reference antenna,the average out-of-band RCSR is about 13d B,and the maximum in-band RCSR is about 17d B.(4)The PIN diode is introduced into the ground plane unit cell for the PRS antenna with RAM,8.1d B-co-and 17.2 d B-cross-polarized RCSRs are achieved by means of the different reflection phase of the ground plane unit cell.(5)The operating bandwidth of the PRS antenna is broaden with the dual-layer complementary reflecting surface.Moreover,both monostatic RCSR and bistatic RCSR are obtained with the RAM and band stop FSS ground plane.(6)Since the EBG structure can reduce RCS and suppress the surface wave by its phase and frequency band gaps,a checkerboard surface(CS)is placed on the top surface of an antenna array,to enhance the aperture efficiency and reduce the RCS.In order to verify our thought,a 2×2 slot array is fabricated as an example.Measured and simulated results reveal that,compared with the slot antenna array without the CS,the gain enhancement is about 2.1d B.Besides,the average out-of-band RCSR is more than 10 d B,and the maximum in-band RCSR is about 11d B.With the researches on the antenna scattering theory and the characteristics of PES,in this paper,we propose a method which can both enhance the gain and reduce the RCS for antenna and antenna arrays.Moreover,by taking use of the PESs,such as RAM,PRS,EBG and FSS,we make contribution to solving the the contradiction between stealthy characteristic and radiation performance of antennas.