Radiative Deep-Subwavelength Frequency-Selective Surface-Based Cross-Band Decoupling Method for Base Station Antenna

To address the bandwidth limitations encountered by existing decoupling methods during the global integration process of base station antennas, a radiative deep-subwavelength frequency-selective surface (RFSS)-based cross-band decoupling method is proposed. The RFSS is formed by a deep-subwavelength FSS whose external profile is defined by a well-optimized narrow frame. It is implemented to not only be transparent for high-band (HB) electromagnetic waves but also effectively radiates low-band (LB) ones. To validate this concept, a dual-band base station antenna, which comprises an RFSS-based LB antenna and a $2 \times 2$ HB subarray, is proposed. Furthermore, we undertake a detailed analysis of the operational mechanism underlying the proposed RFSS-based LB antenna. In addition, a prototype for proof of concept is fabricated and measured. The results demonstrate that the LB antenna operates within a relatively wideband of 1.4–2.7 GHz (63.4%), featuring a low profile of $0.25\lambda _{lc}$ (at the center frequency of LB), and the HB antenna operates at 3.3–4.2 GHz (24%).