Miniaturized Wideband ±45° Dual-Polarized Metasurface Antenna by Loading Quasi-Fractal Slot

A miniaturized wideband metasurface antenna with ±45° dual-polarization is proposed. The metasurface (MTS) is comprised of an array of 3 × 3 square patches. A pair of coaxial probes feeds the corner-truncated patch underneath the MTS while keeping the floor intact; ensuring that less energy is radiated in the backward direction. To realize miniaturization of the MTS radiation element and maintain dual-polarized radiation performance, each square metal patch is loaded with a symmetrical quasi-fractal slot. By changing the current path of each patch, the resonant frequency of the MTS is decreased, and the electrical size is reduced. Characteristic mode analysis (CMA) is utilized to explain and analyze the miniaturization mechanism of the MTS. In order to prove the theoretical results, a prototype with the radiation element size of 0.39λ ₀ × 0.39λ ₀ (λ ₀ is the wavelength in free space at the center operating frequency) is fabricated. The measured bandwidth is 18.6% (4.98–6.00 GHz) with | S ₁₁ | < −10 dB, | S ₁₂ | < −16 dB, boresight gain of 6.12–7.45 dBi and front-to-back ratio better than 20 dB.