Dual-Band Shared-Aperture Antenna Design with Circular Polarization

The schematic diagram of the proposed dual-band shared-aperture antenna is presented in Fig. 1. In this study, we aim to design a dual-band circularly polarized (CP) antenna with broadside radiation for both frequency bands. To achieve this, we adopt a co-design approach combining a reflective array (RA) and a frequency selective surface (FPC) antenna.

The designed antenna structure consists of a top feeding source, a multifunctional metasurface, a bottom feeding source, and a bottom ground. At high frequencies, the metasurface acts as a reflective surface, reflecting electromagnetic waves while introducing a 90ﾰ phase difference between the two orthogonal electric field components using an inserted polarizer. This configuration enables the antenna to generate a high-gain circularly polarized beam in the millimeter wave band.

Simultaneously, at low frequencies, the metasurface functions as a partially reflective surface (PRS), forming an FPC in conjunction with the feeding source and the bottom ground. The operating principle of the FPC is as follows: when the electromagnetic waves from the feeding source reach the metasurface, a portion of them is reflected back to the cavity, while the rest is transmitted through the surface. The reflected waves oscillate within the cavity and, upon superimposition, form an in-phase wave front distribution, resulting in a directive beam. Additionally, the polarizer on the surface induces two orthogonal electric field components with the same magnitude and a phase difference of 90ﾰ in the outgoing wave, thereby achieving circular polarization for the FPC antenna.