Design of Broad-Angle Low-RCS Microstrip Antenna for Dual-Polarization Using Characteristic Mode Analysis

In this paper, a broad-angle low-scattering microstrip antenna for dual-polarization is designed based on characteristic mode analysis (CMA). The modal analysis of the reference antenna under dual-polarization incident plane waves is first carried out to guide radar cross section (RCS) reduction (RCSR) design in broad-angle range. Then, through the modifications on the radiation patch and ground, the modal currents of the important scattering modes in broad-angle range are cut off. Hence, a broad-angle low-RCS aperture-coupled microstrip antenna for dual-polarization is obtained. However, the radiation performance decreases due to the ground modification. A frequency selective surface (FSS) structure is designed and fills in the ground modification areas. With the FSS structure, the proposed antenna shows a good radiation and scattering performance. A low-RCS antenna prototype is fabricated and tested. The antenna works from 2.79 GHz to 2.87 GHz (2.82%), and the gain is 6 dBi at 2.84 GHz. For the co-polarization, it can realize RCSR from 0° to 90°, and the average and peak RCSRs are 9.0 dB and 17 dB, respectively. For the cross-polarization, it can realize RCSR from 0° to 18° and 22° to 90°, and the average and peak RCSRs are 5.0 dB and 20 dB, respectively. In the meantime, its transmission and radiation performance keeps well. The measured and simulated results are in good agreement, which validates the design.