Dual-band Reflectarray Antenna With Low Radar Cross Section Based On Three-dimensional Frequency Selective Surface

Reflectarray antennas are commonly employed in long-distance communication.Decreasing the radar cross-section of antennas can bolster the military strike resilience of communication equipment.A three-dimensional frequency selective surface(3D-FSS)is an array structure that consists of multiple units arranged periodically or quasi-periodically.It is capable of selectively and efficiently controlling the incidence of electromagnetic waves with different polarizations and frequencies.Compared to the traditional two-dimensional FSS,the 3D-FSS has lower sensitivity to oblique incidence and can provide stable phase and amplitude responses even when exposed to large-angle incidence,making it advantageous for reflectarray antenna applications.Additionally,the design of3D-FSS can be guided by its corresponding equivalent circuit model,allowing for the integration of more functionalities.This article presents the design process of a general dual-frequency reflect array using 3D-FSS as the array unit and guided by the equivalent circuit model.Two dual-frequency reflect array antennas with low radar cross section(RCS)have been designed as follows:(1)A dual-band reflectarray antenna with low RCS,which is designed as an absorptive and reflective separation structure,is composed of an FSS and an absorptive layer.The upper layer adopts a two stop-bands FSS based on stacked microstrip lines,while the lower layer is made of a paperbased honeycomb absorber,which can control the amplitude and phase of the incident electromagnetic wave.The upper stop-band FSS provides a 360° phase shift range at 5.2 GHz and9.5 GHz and generates two stop-bands and three pass-bands in the frequency range of 0 GHz to 13 GHz.The upper stopband has a loss of less than 3 d B in the frequency range from 4.69 GHz to 5.74 GHz,with a relative bandwidth of 20.13%,and a range of 8.74 GHz to 10.97 GHz with a relative bandwidth of 22.62%.When the electromagnetic wave frequency is within the range of 2.5 GHz to25 GHz,the absorber in the lower layer can absorb 90% of the energy.With the coordinated operation of the upper and lower layer structures,the designed reflect array antenna can work simultaneously at 5.2 GHz and 9.5 GHz,achieving gains of 27.44 d Bi and 28.45 d Bi,respectively.The RCS reduction can reach-10 d B in the frequency range of 1 GHz to 13 GHz.(2)A dual-band low RCS reflectarray antenna with integrated absorption and reflection was designed.The reflectarray unit cell is composed of a lossy resonant cavity loaded with phase-shifting slots,which provides a phase shift range of 320° within the operating frequency band while exhibiting absorption characteristics outside the band.During the array formation,the radiation pattern of the feeding antenna was modeled,and the aperture efficiency of the reflectarray antenna was analyzed to determine the position of the horn feed.The designed reflectarray antenna operates simultaneously at5 GHz and 9 GHz,achieving gains of 24.8 d Bi and 29.8 d Bi,respectively.When the incident wave is horizontally polarized electromagnetic wave,the radar cross-section of the reflectarray antenna can be reduced by-10 d B compared to the radar cross-section of an equally-sized PEC at 1.3 GHz-5.7GHz and 6 GHz-8.7 GHz,with relative bandwidths of 125.7% and 36.7%,respectively.When the incident wave is vertically polarized electromagnetic wave,the reflectarray antenna can achieve a-10 d B reduction in radar cross-section at 1.65 GHz-7.5 GHz and 10.5 GHz-13.3 GHz,with relative bandwidths of 127.9% and 23.5%,respectively.