4-Port MIMO antenna with novel isolator conducting structure for sub-1 GHz/sub-6 GHz and RF-energy harvesting applications

A 4-port MIMO antenna with a novel isolator structure for sub-1GHz/sub-6GHz and RF-energy harvesting applications is presented in this research. The proposed antenna is investigated systematically at 2.6 GHz design frequency with four distinct stages: STEP-1, STEP-2, STEP-3 and STEP-4 and an optimal design (STEP-4: $ 0.5\lambda \times 0.7\lambda \times 0.014\lambda $ 0.5λ×0.7λ×0.014λ mm3) is chosen for further study. A unique isolation structure was developed between two identical elements separated by $ 0.077\lambda $ 0.077λ, resulting an improved isolation of greater than 14 dB at 0.9 GHz and greater than 18 dB at 2.6 GHz is obtained. The suggested antenna resonates at 900 MHz-simulated & measured and 2.6 GHz-simulated & 2.8 GHz-measured with simulated fractional bandwidth/resonating band of 24.6%/0.778–1 GHz & 20.7%/2.4–2.94 GHz and a measured fractional bandwidth/resonating band of 17.8%/0.83–0.99 GHz & 21%/2.41–3 GHz at lower and upper resonating frequencies respectively. A peak gain of 1.5 dB at 900 MHz and 4.2 dB at 2.8 GHz has been obtained. The SAR values of less than 0.5 and 1.6 W/kg and radiation efficiencies of 74.7% and 90% at 900 MHz and 2.8 GHz were obtained, respectively. The suggested antenna's MIMO performance is simulated using electromagnetic tool HFSS in terms of ECC, DG, TARC, MEG and CCL, and the obtained results are experimentally verified. Further, the proposed antenna is tested for harvesting applications wherein 9.5 mW of harvested power, 76.45% power conversion efficiency (PCE), 4V harvested voltage, current 2.4mA and 12.46 mW Friis equation output at 915 MHz and 26.98 mW of harvested power, 69.5% power conversion efficiency, 5V harvested voltage, current 5.4 mA and 38.8 mW Friis equation output at 2.5 GHz are recorded.