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Due to the influence of mutual coupling between the antenna elements, the scanning performance of planar phased array antenna deteriorates significantly with the increase of scanning angle, which limits the ability of an antenna to detect targets at low elevation angles. A scan gain enhancing surface (SGES) consisting of a holographic metasurface (HM) and a surface-wave guiding structure (SWGS) is proposed in this letter. HM is loaded at both ends of the phased array, which can convert surface waves into leaky waves and radiate in the specified direction, thereby enhancing the beam gain of the phased array. The SWGS can promote the surface-wave propagation to the HM, thus improving the surface-wave conversion efficiency. An eight-element patch linear array was designed and fabricated to verify the effectiveness of the SGES. The measurement results show that the antenna array loaded with SGES can scan up to ± 57° with only 0.4 dB reduction in realized gain. The realized gain can be increased by up to 3.6 dB. Good agreement is obtained between the measurements and the simulations.

This letter introduces a transmission frequency selective surface (FSS) with excellent roll-off feature, ultrathin thickness, low insertion loss, and wide rejection bands. Three novel basic component structures are developed based on the polarization rotator structure leading to multitransmission zeros and poles that can be independently controlled. Theoretical analyses and simulations are carried out, and a prototype is fabricated and measured. The proposed FSS exhibits double sharp roll-off sidebands, ultrathin thickness and low insertion loss, as well as two wide stopbands. In addition, the proposed FSS shows stable responses with oblique incidence up to 45$^\circ$. As a result, the tight agreement between measurement and simulation validates the design principle.