A novel enhanced FBR and low SAR MIMO antenna with limited ground plane for wearable devices

This study explores a novel approach to mitigate the challenge of a small ground plane inducing substantial back lobes in high front-to-back ratio (FBR) microstrip patch antennas. Introducing a combined technique employing rectangular strip and connecting strip methods, this research aims to counteract backward radiation by generating supplementary magnetic currents through an inductive effect. The hybrid method effectively reduces the backward radiation from the original patch. The proposed single antenna element occupies a notably smaller area (approximately 0.029 λ × 0.036 λ, where λ denotes the cutoff wavelength at 5.9 GHz), making it particularly suitable for wearable applications. Additionally, an equivalent circuit model illustrates the coordinated action, offering comprehensive insights into the physical mechanisms. The achieved FBR surpasses directivity by up to 6.03 dB, leading to a diminished specific absorption rate (SAR) when worn while maintaining minimal impact on radiation efficiency due to human presence, a crucial quality for wearable devices.