Compact Dual-Band Dual-Polarized Monopole Antennas Using Via-Free Metasurfaces for Off-Body Communications

This letter presents a novel approach to design metasurface-based dual-band dual-polarized monopole antennas at 2.4 GHz ISM and 3.5 GHz WiMAX-band for off-body communications. The behavior is modeled with an array of unit-cells excited by a truncated monopole structure. A rectangular via-free unit-cell (RVU) is theoretically developed using a transmission-line model to exhibit an AMC-like characteristic. Following that, by controlling the RVU dispersion curve, two distinct unit-cells, UC $_{1}$ and UC $_{2}$ , are optimized to construct the metasurfaces of size 3 × 3 (MS $_{1}$ ) and 2 × 2 (MS $_{2}$ ), respectively, which generate TM $_{10}$ mode in the lower band (LB) and TM $_{20}$ mode in the higher band (HB). Then, these metasurfaces are excited by four variant truncated monopole structures to design four dual-band dual-polarized antennas (A $_{1}$ , A $_{2}$ , A $_{3}$ , and A $_{4}$ ). A $_{1}$ and A $_{3}$ are MS $_{1}$ -based, whereas A $_{2}$ and A $_{4}$ are MS $_{2}$ -based. A $_{1}$ and A $_{2}$ are designed to produce circular-polarization (CP) in the LB, whereas A $_{3}$ and A $_{4}$ are designed to produce CP in the HB. In A $_{1}$ and A $_{2}$ , additional 0.25 ${\lambda _{g}}$ diagonal slots are used to enhance impedance-bandwidth in the LB. All the antennas produce a wide impedance-bandwidth and high gain with low SAR. A $_{1}$ is fabricated using a felt substrate and measured, which shows good agreement with simulations.