A Reflectarray Antenna Designed with Gain Filtering and Low-RCS Properties

This paper presents a reflectarray (RA) antenna operating at X-band with gain filtering and low radar cross section (RCS) properties. The unit cell (UC) for the proposed RA antenna design combines a band-notched absorber unit and a dielectric lens unit together, where the dielectric lens unit serving as a phase shift is seamlessly coating on the absorber unit to achieve co-design. Importantly, it is required that the UCs should still maintain the high notch-band-edge selectivity property that the band-notched absorber originally has when the profile of the dielectric lens unit is varied to cover a full phase-cycle (2π) for the proposed RA antenna design. For demonstration, an absorber is presented with a high notch-band-edge selectivity and a wide absorption bandwidth performance in vertical and horizontal polarization, respectively; a dielectric lens based on square posts is rigorously designed to be coated on the absorber seamlessly to construct the desired UC. The simulated results show that the proposed RA antenna has a bandpass-like gain filtering performance and pencil-beam radiation patterns within the notch band, which is experimentally verified by the measured results. In addition, the measured results also reveal the RCSs of the proposed RA antenna are reduced significantly compared to counterparts of the conventional RA antenna in horizontal polarization and out of the notch band in vertical polarization.