In this paper, a novel shared-aperture method of electromagnetic metasurface and antenna is proposed to obtain low radar-cross-section (RCS) performance. This method first designs low-RCS metasurface and conventional antenna independently, and then obtains novel low-RCS antenna by combining this metasurface with conventional antenna based on shared-aperture technique. Besides, current analysis and consequent local structure modification are also conducted to guarantee the antenna’s good radiation performance and broadband RCS reduction in the meantime. Using this method, a dual-layer polarization rotation unit cell is first proposed and its broadband working principle is investigated by both theoretical analysis and numerical comparison. Based on this unit cell, a broadband low-RCS metasurface is constructed. Then an initial shared-aperture metasurface antenna is obtained by substituting the middle cells in the metasurface with conventional patch antenna directly. Through careful analysis of surface current in radiation mode, the gain decrease of this metasurface antenna is revealed. On this basis, a limited removing strategy is put forward and some metasurface cells in the antenna is removed with the aid of current analysis. Consequently, an improved shared-aperture metasurface antenna is proposed. (The design flow of this metasurface antenna is displayed in the following Fig. 1) This improved antenna works from 6.3 GHz to 7.48 GHz, which is a bit wider than conventional patch antenna. Its gain is also higher than conventional antenna with the maximum improvement of 1 dB. Meanwhile, apparent RCS reduction is obtained from 6 GHz to 16 GHz for any polarized incident wave, and the reduction peak is larger than 20 dB. Fabrications and measurements are finally conducted. The good agreements of measured results and numerical calculations are achieved. The well-behaved radiation performance and broadband low-RCS property of this metasurface antenna verify the effectiveness of the proposed method. Different from most reported design method of low-RCS antenna directly from conventional antenna, the proposed method adopts a reverse thinking and converts the scattering optimization to radiation optimization, realizing the integration of metasurface and antenna, and making the design of low-RCS antenna easier and faster.
