Flexible four-port MIMO antenna loaded with frequency selective surface for on-body applications

This work reports a dual-band four-port MIMO antenna loaded with a 5 x 5 frequency-selective-surface (FSS) of size 72.5 mm×75.0 mm for gain enhancement. The antenna uses a novel radiating-patch and a modified rectangular-ground printed on a 0.254 mm thickness Rogers substrate, generating bandwidths of 4.04-6.64 GHz and 7.44-16.60 GHz with overall dimensions of 30.0 mm×30.0 mm. The FSS, which is printed on FR4 1.60 mm substrate, is placed below the antenna at a distance of 15.0 mm, which records a maximum peak-gain of 10.77 dBi. The characteristics-mode-analysis _DWA (CMA_DWA) is simulated by subjecting the antenna to 10 modes, with Mode-2, Mode-4, Mode-5, Mode-6, Mode-7, and Mode-9 being the significant modes with modal significance values more than 0.707 and generating six resonance values at 6.67 GHz, 7.20 GHz, 7.958 GHz, 8.76 GHz, 9.20 GHz, and 11.80 GHz. The four identical radiating patches are arranged in orthogonal sequence, achieving spatial-diversity performance with ECC_DWA ≤ 0.07 (Band-A), 0.03 (Band-B), DG_DWA≥ 9.70dB (Band-A), 9.85dB (Band-B), TARC_DWA≤ -5.0dB (Band-A), -2.50dB (Band-B), CCL_DWA≤ 0.38 b/s/Hz (Band-A), 0.30 b/s/Hz (Band-B), and the difference between the MEG_DWA of two-ports to be ≅0.0dB. The SAR_DWA value corresponds to 0.158 W/Kg at 5.50 GHz, 0.076 W/Kg at 5.90 GHz, 0.0503 W/kg at 7.50 GHz, and 0.24 W/Kg at 10.0 GHz with conformal angles of 15^o, 30^o, and 45⁰, retaining the operational bandwidth.